High Temperature Issue While Driving

[Streetr]

Dave is absolutely correct regarding the difficulty of getting all of the water and old glycol out. I end up blowing as much of the old coolant out of the system as possible and then using the Evans Prep fluid to finish the job. It’s labor intensive, messy and pricey so I tend to do the change to Evans Coolant when I’m replacing a water pump or replacing some other significantly coolant invasive component. Aluminum doesn’t mind being at 120 or 150C, the main issue is that regular glycol based coolant or water has to be under pressure so that it doesn’t boil during engine operation at normal operating temperatures...and If we exceed our normal operating temperatures the risk becomes that the engine develops vapor (steam) pockets in the hotest locations in the cylinder heads (usually around the exhaust valve cooling passages), forcing the coolant or water away from that “hot spot”. The hot spot then exceeds the 200C temperature where aluminum starts to be affected. With Evans coolant (boiling point of 190C at 0 psi) if something causes our coolant temperatures to exceed our normal operating range, even by a fairly large amount, there is very litte risk of engine damage since the steam pockets are unlikely to form until much higher engine temperatures are reached (Over 150C). We’ve seen this on all aluminum Porsche 944 engines where an engine on the track would have been destroyed with normal coolant, but were unharmed when coolant temperatures exceeded 132C due to an airflow blockage on the front of the car.

Changing my 500E to Evans Coolant wasn’t too bad, actually. The old coolant is relatively easy to remove (especially when replacing a water pump). The toughest car I’ve seen is a 2015 VW TDI Golf.

Hope this is helpful.

 

[Gullwing]

Thank you all for the helpful advice and the very valuable comments. Really appreciate it!

With regard to the fan clutch, I managed to track down an original Sachs fan clutch (the one on the far right on the photo posted by @gsxr). The part is NOS. On the photo there is a number on it which could be a date (08/02) so could be August 2002? Am not sure if that is a date or just a number.
Am considering to buy it even though I have already ordered the ACM fan clutch.
Would you guys recommend to buy and install the original Sachs clutch or shall I stay with the ACM?

 

[gerryvz]

@Gullwing, it is a fact that many if not most of the E500E fan clutches were actually defective from the factory, and often never activated correctly even when new. And this goes for replacement fan clutches from Sachs, and more recently Horton (a division of Sachs) clutches. So for many cars, they ALWAYS ran hot even when new.

The ACM clutchs seem to work MORE correctly (not perfectly) but activate earlier and stay on longer than the factory clutches did (per the design when they actually work as they are/were supposed to).

I have heard stories of a couple of folks here on the forum who know how to make adjustments to the factory fan clutches to get them to work correctly, or much closer to how they were designed to. But I have never actually seen a modified clutch in this way. It seems to be a very dark and lost art.........only known by one or two people in the world about how to do.

So I think the easiest solution is to get the ACM clutch, which will pretty much work out of the box.

 

[Streetr]

@Gullwing, it is a fact that many if not most of the E500E fan clutches were actually defective from the factory, and often never activated correctly even when new. And this goes for replacement fan clutches from Sachs, and more recently Horton (a division of Sachs) clutches. So for many cars, they ALWAYS ran hot even when new.

The ACM clutchs seem to work MORE correctly (not perfectly) but activate earlier and stay on longer than the factory clutches did (per the design when they actually work as they are/were supposed to).

I have heard stories of a couple of folks here on the forum who know how to make adjustments to the factory fan clutches to get them to work correctly, or much closer to how they were designed to. But I have never actually seen a modified clutch in this way. It seems to be a very dark and lost art.........only known by one or two people in the world about how to do.

So I think the easiest solution is to get the ACM clutch, which will pretty much work out of the box.

I ran into an interesting issue lately with a radiator. It was a 2002 Audi TT that had been very well-maintained. One of the electric cooling fans had failed so I replaced it, expecting the higher than normal Coolant temperature to return to normal. The new fan operating correctly, but the higher than normal coolant temperature persisted. These cars usually run dead square in the middle of the gauge regardless of the ambient temperature or driving circumstances (keep in mind that many new car temperature gauges are representative rather than exact-they indicate exactly in the center of the gauge as long as the specified range of normal temperature is detected by the engine control unit). By checking the coolant temperature on the inlet side of the radiator versus the coolant temperature on outlet side of the radiator I was able to determine that the radiator simply was not exchanging heat between the coolant and the air even though the air path was clean. I replace the radiator and the problem was resolved. The old radiator looked very good inside except under magnification where it appeared there was a film that had chemically bonded to the aluminum core. Definitely had me scratching my head for a while.

 

[gsxr]

I ran into an interesting issue lately with a radiator. ... By checking the coolant temperature on the inlet side of the radiator versus the coolant temperature on outlet side of the radiator I was able to determine that the radiator simply was not exchanging heat between the coolant and the air even though the air path was clean. I replace the radiator and the problem was resolved. The old radiator looked very good inside except under magnification where it appeared there was a film that had chemically bonded to the aluminum core. Definitely had me scratching my head for a while.

I've had similar experiences as @Streetr described above... in rare instances, a radiator (sometimes not that old!) simply does not transfer heat as it should, despite looking perfect externally and flowing normally from inlet to outlet. I don't know what causes the film/buildup internally, which cannot be easily seen. On the flip side I've also had a couple cars sort of similar to Gullwing's experience where they ran hotter than expected (but not nearly as severe as his case), despite a new radiator and all sorts of other work done. I've always wondered if the "film" on the inside of the radiator, might also be present on the inside of the block/heads?

But anyway - Gullwing reported that a new Behr was installed and still didn't cure the problem.

 

[gerryvz]

I've had similar experiences as @Streetr described above... in rare instances, a radiator (sometimes not that old!) simply does not transfer heat as it should, despite looking perfect externally and flowing normally from inlet to outlet. I don't know what causes the film/buildup internally, wh ich cannot be easily seen. On the flip side I've also had a couple cars sort of similar to Gullwing's experience where they ran hotter than expected (but not nearly as severe as his case), despite a new radiator and all sorts of other work done.

But anyway - Gullwing reported that a new Behr was installed and still didn't cure the problem.

I had a major hot running problem with my G320 (M104 engine) a couple of years back. The higher the speed driven and more the load, the hotter things would get (110-120C indicated!!). I replaced the (very expensive G-wagen specific) radiator with a new one. No change.

It ended up being a faulty thermostat. Now I cannot get the G-wagen above ~92C indicated in any condition or ambient temp.

 

[Streetr]

I had a major hot running problem with my G320 (M104 engine) a couple of years back. The higher the speed driven and more the load, the hotter things would get (110-120C indicated!!). I replaced the (very expensive G-wagen specific) radiator with a new one. No change.

It ended up being a faulty thermostat. Now I cannot get the G-wagen above ~92C indicated in any condition or ambient temp.

The thermostat issue on my 500E caused mine to run cool in the winter and too warm in the summer. Turned out the thermostat was stuck in about a 90% open position.

 

[maw1124]

110°C engine temp is about the most I'm comfortable with, although technically MB says it's safe to 120°C. Personally, I'd shut the AC off and run the heater on max when engine temps hit indicated 115°C. I think 110C is hotter than it should be assuming there is normal airflow with mechanical fan roaring and electric fans on high speed, even in 45C/110F ambients.

$.02 that I can add here, as my car has been in FL for over 20 years… I see 100* all the time (air on or off, highway speed or stopped, full load oe loafing, yadaX3)… and another longtime FL 500E owner / mechanic has told me not to worry about it until the temps hit the red for sustained times… he’s also worked on MB’s since the 70s beginning with a 6.3… he says they were designed for it, that MB engineers take those temps seriously, not as indicators of potential trouble... that is, RED means trouble and nothing else does… so while I tend to think “cooler is better all the time” (coming from the S55 “more boost but watch IAT” world), his advice has proved sage. If there was a larger flowing radiator for this car I might be interested but not because I need it. And I run the car hard on freeways (3rd to WOT upshift) pretty routinely.

That’s a long way of saying I agree with @gsxr on the temps I’m comfortable with.

Cheers,

maw

 

[gerryvz]

I had my E500 out late last week in some hot (90F+) ambient temps with high summer humidity, with A/C running full blast. Stop and go traffic, freeway, arterials. I did not see my needle go above 100C in any condition. This is after I got the low speed fans working (blown fuse) as part of my A/C compressor diagnosis and install.

Typical running temps with the car moving were 90-95C. At stoplights, 98-100C indicated.

Every major component in my cooling system was replaced with new last year as part of my COVID project -- Behr radiator, MB/Horton factory fan clutch, Graf water pump, Wahler thermostat, MB expansion tank, MB heater hoses, etc.

What I have deduced from all of this is that the low-speed fans (which operate most of the time when the A/C is on) are very important augmentors to the fan clutch in controlling temperatures. I would say that just the low-speed fans by themselves reduce the temp probably about 5C -- just about negating the ~5C INCREASE in system temp that happens when the A/C is operating.

I'll continue to monitor things the rest of this summer, but I'm very happy with the overall reduction in cooling temps. Before I found the blown fuse in the low-speed aux fan relay behind the fuse box, it was not unusual at all to see temps of 105-110C indicated, in high speed driving and at stop lights, with the A/C running; and 100-105C indicated with no A/C running.

If there's a hot running problem, the first thing I would ALWAYS do would be to check the operation of the low-speed and high-speed fans, as well as the associated fuses for the system.


@maw1124 -- I agree that the cars can run for extended periods at 110-115C+ (my G-wagen did it for 18+ months with no apparent ill effects), but I do believe this is too high and more than the system was designed to run at.

 

[Streetr]

I had my E500 out late last week in some hot (90F+) ambient temps with high summer humidity, with A/C running full blast. Stop and go traffic, freeway, arterials. I did not see my needle go above 100C in any condition. This is after I got the low speed fans working (blown fuse) as part of my A/C compressor diagnosis and install.

Typical running temps with the car moving were 90-95C. At stoplights, 98-100C indicated.

Every major component in my cooling system was replaced with new last year as part of my COVID project -- Behr radiator, MB/Horton factory fan clutch, Graf water pump, Wahler thermostat, MB expansion tank, MB heater hoses, etc.

What I have deduced from all of this is that the low-speed fans (which operate most of the time when the A/C is on) are very important augmentors to the fan clutch in controlling temperatures. I would say that just the low-speed fans by themselves reduce the temp probably about 5C -- just about negating the ~5C INCREASE in system temp that happens when the A/C is operating.

I'll continue to monitor things the rest of this summer, but I'm very happy with the overall reduction in cooling temps. Before I found the blown fuse in the low-speed aux fan relay behind the fuse box, it was not unusual at all to see temps of 105-110C indicated, in high speed driving and at stop lights, with the A/C running; and 100-105C indicated with no A/C running.

If there's a hot running problem, the first thing I would ALWAYS do would be to check the operation of the low-speed and high-speed fans, as well as the associated fuses for the system.


@maw1124 -- I agree that the cars can run for extended periods at 110-115C+ (my G-wagen did it for 18+ months with no apparent ill effects), but I do believe this is too high and more than the system was designed to run at.

Gerry. Those are about the temperatures I see on my 500E. Aside from a few seconds after a hot restart, I don’t recall seeing my temps above 100 C since I replaced my defective thermostat, at which time I switched over to Evans Coolant.
I have a new challenge at the moment. I was getting ready to go through my transmission valve body last night and I dropped the valve body. I have done countless valve body rebuilds and transmission overhaul’s and I’ve never dropped or damaged anything. I managed to break the selector shaft and where it sticks out of the valve body. I haven’t found the spring loaded reed valve yet, either. Challenges and opportunities. I will figure it out.

 

[gerryvz]

Ouch. I'm sure that you can get a replacement selector shaft. I believe that the @gsxr may have a couple of "parts" quality valve bodies, that may have donate-able parts. Please query him about spare/replacement for the selector shaft and anything else you need.

Glad to hear that your temp experience is similar to mine.

I have always found it normal for when a parked car (that has been run) first starts up, the temp spikes high, but then quickly comes back down as coolant begins circulating.

Does the Evans Coolant make a significant difference in temps overall, above the Zerex G05?

 

[gsxr]

... another longtime FL 500E owner / mechanic has told me not to worry about it until the temps hit the red for sustained times… he’s also worked on MB’s since the 70s beginning with a 6.3… he says they were designed for it, that MB engineers take those temps seriously, not as indicators of potential trouble... that is, RED means trouble and nothing else does…

I was told the basically same thing by the dealer back in the late 90's with my hot-running 87 300D that was constantly at 110-115C engine temp in 100F+ ambients. "Don't worry about it unless it's in the red (over 120C)".

The problem is, there's a difference between "not dangerous", and "not normal". For all years/models of 124 regardless of engine, if the cooling system is in top shape and can hold the full 1.4 bar rated pressure, the statement it is "not dangerous" up to 120C is accurate. But those temps are not normal.

When everything is working correctly (i.e., factory new) the temps should be far lower. "Normal" will vary depending on the engine, for example with the OM603.960 300D it should run at 85-95C at all times and never exceed 100C; but on the 500E the high end / never exceed number is 5-10C higher (105-110C). Again, this is for the "normal" range, not "safe" range. I eventually sorted the 300D issues and it runs in the "normal" range again.

 

[gerryvz]

The problem is, there's a difference between "not dangerous", and "not normal". For all years/models of 124 regardless of engine, if the cooling system is in top shape and can hold the full 1.4 bar rated pressure, the statement it is "not dangerous" up to 120C is accurate. But those temps are not normal.

This is an important distinction -- what is "normal" vs. what is "safe" and the car can actually handle. The 20C above the 100C mark is a pretty large safety margin.

I believe for the E500E, with a more or less properly operating cooling system:

• "Normal" temps are from 90-105C depending on a variety of external factors
• "Safe" temps are up to 115C for prolonged operation, but not advisable

 

[maw1124]

I agree with all of this… I don’t think I’ve ever seen mine over 100*C… but until it got halfway to 120*C it wouldn’t register to me to even think about it, was the point of my comment… 105*C is a non-occurrence basically.

But if and when I ever need a thermostat, @jhodg5ck sage advice will be implemented.

maw

 

[gsxr]

Yup! Agree 100% with both of the above posts.

 

[Streetr]

Ouch. I'm sure that you can get a replacement selector shaft. I believe that the @gsxr may have a couple of "parts" quality valve bodies, that may have donate-able parts. Please query him about spare/replacement for the selector shaft and anything else you need.

Glad to hear that your temp experience is similar to mine.

I have always found it normal for when a parked car (that has been run) first starts up, the temp spikes high, but then quickly comes back down as coolant begins circulating.

Does the Evans Coolant make a significant difference in temps overall, above the Zerex G05?

 

[Streetr]

Correct. Heat soak is absolutely normal. Modern cars are designed to register any temperature that is in a normal, expected range by basically placing the temperature gauge needle in the middle. These gauges are referred to as „representative rather than exact“. Our classic Mercedes register the actual temperature.
Thanks for your thoughts on the transmission parts. Good thinking. I will check with him.

 

[Streetr]

Ouch. I'm sure that you can get a replacement selector shaft. I believe that the @gsxr may have a couple of "parts" quality valve bodies, that may have donate-able parts. Please query him about spare/replacement for the selector shaft and anything else you need.

Glad to hear that your temp experience is similar to mine.

I have always found it normal for when a parked car (that has been run) first starts up, the temp spikes high, but then quickly comes back down as coolant begins circulating.

Does the Evans Coolant make a significant difference in temps overall, above the Zerex G05?

Regarding the Evans Coolant. Technically it doesn’t quite have the heat transfer ability of typical Ethylene glycol coolants. However, I have used it in numerous cars and have not noticed a change in actual coolant temperatures. The main reason I use it is due to the benefit of being able to run zero pressure in the cooling system and having a boiling point of over 360 F. I’m sure you can imagine the benefit of having zero pressure on your cooling system as far as a reduction in system stress. Everything from hoses to water pumps essentially become flow devices as opposed to flow and pressure containment devices. The biggest issue was getting all of the old coolant out. I use low pressure air to blow as much coolant out as I can and then I use the Evans prep fluid to do the final rinse out. Because of this, I generally switch things over to Evans Coolant when I’m replacing something like a radiator or water pump. Evans Coolant will develop a low amount of pressure on its own if you leave the coolant cap in its normal, fully closed position. On my 500 E I leave the coolant cap in its first lock position so that no pressure is developed. I do the same thing on the Porsche 944 system. On cars with a screw down coolant cap, such as Audi and later Porsches, I remove the gasket from the coolant cap.

 

[Gullwing]

Guys I have reached a dead end. The problem is still there. Just to recap - have changed the radiator, thermostat, fan clutch to Behr and now to ACM as well as the expansion tank cap. Test drive today at 42 Deg. C. ambient temp. again indicated a temp. of between 110-115 Deg. C.
I am puzzled. Returning from the test drive and checking with an IR Temp gun at different locations showed temperatures of 88, 94.2, 93.2 and 89 Deg. C.
Am not sure what to do next. Can anything else be causing these higher temperatures? Any of the 3 temp. sensors or the air intake sensor?
Should I get an OBD1 diagnostic tool and read out the codes? Will that gave me any useful information to solve this problem?

 

[JC220]

This is looking increasingly like another subject matter which we require a large white Paper PDF report on

 

[gsxr]

You should have an OBD-1 blink code reader to help with general diagnostics, and you should confirm there are no recurring codes, but it's unlikely to reveal any useful information / smoking gun cause of the hot running. This is cheap and easy though, and you have nothing to lose at this point.

Next step, IMO, is confirming the dash gauge is accurate since an IR temp gun is showing much lower temps than the dash gauge. If you have access to live data, see if the temps reported by the LH or EZL match the dash gauge. The numbers should be within ±2°C or so, very very close.

If you don't have access to live data, get the engine up to ~100C, unplug each of the 3 temp. sensors at the intake manifold, and measure the resistance with an ohm meter. Use the attached PDF files as a reference for what resistance to look for at a given temp. All three should read very close together in temperature, after converting from ohms to degrees. The air intake sensor behind the headlight can also be checked but should have little to no effect on engine operating temps, AFAIK.

If the engine really is 110-115C, and you are positive the condenser fins are not blocking airflow, and the fan shroud is in place with all rubber flaps in place, and the fan is roaring... my final ideas are:

1) Replacing the t-stat (again) as people have reported receiving defective t-stats out of the box
2) Modify the t-stat by drilling 2 small holes near the ball valve as described in this thread starting at post #29
3) Performing a citric acid flush to remove scale in the cooling system (this is time consuming and requires multiple flushes afterwards)




EDIT: Attached PDF files.

 

[gerryvz]

I believe you need to bring the car to a specialist who can properly diagnose each component of the system. Yes, these cars run hotter than other W124s, and this is because of the size of the engine in the engine compartment, and lack of airflow. And this is exacerbated in higher ambient temps.

However, as I have finally found, with new components, the system DOES run cooler when things are diagnosed and working properly. I believe that 110+C indicated temps is not normal, and that something is not correct with your system.

In my case, I found that the low-speed fan was not working because of a blown fuse, when the A/C was working.

I think you need to find someone who can methodically evaulate each component of the system, as well as the system as a whole.

 

[Gullwing]

@gsxr
Thanks for tour support and advice which steps to carry out next. I will get the workshop to check the temp. sensors as per the procedure you outlined.
One more point I was thinking about is that I have this temp. issue since the MAF was replaced. My MAF was faulty and engine was running extremely rich with CO readings of 10.00. Temp at that time was in the normal range. Could the faulty MAF have masked the problem of the temp. issue? There must be some connection. I have also previously replaced the upper and lower wiring harness as they were still original and the car has the cooling harness installed. Am just racking my brains.

 

[gsxr]

One more point I was thinking about is that I have this temp. issue since the MAF was replaced. My MAF was faulty and engine was running extremely rich with CO readings of 10.00. Temp at that time was in the normal range. Could the faulty MAF have masked the problem of the temp. issue? There must be some connection.

This is pertinent information. ^^^

Was the replacement MAF new or used? How was it determined to be working correctly, other than not triggering a fault code? The only way to test the MAF is view live data, along with knowing what values are normal. Along the same lines, how old is the O2 sensor? Mixture is controlled primarily by MAF+O2.

As a very rough test, you could disconnect the MAF and go for a test drive. The engine may have a bit less power with MAF disconnected and it will trigger a fault code, but if engine temps drop dramatically, something may be fishy with the MAF. If there's no change in temps, the MAF may be ok. Again, live data would be more accurate. If you try this, clear the MAF fault code afterwards.

I have also previously replaced the upper and lower wiring harness as they were still original and the car has the cooling harness installed. Am just racking my brains.

The harness replacement shouldn't have any effect unless something was done incorrectly, but I'd expect other problems besides high coolant temps. And the "cool harness" which runs the electric fans on high speed would just mask the problem slightly.

 

[Gullwing]

This is pertinent information. ^^^

Was the replacement MAF new or used? How was it determined to be working correctly, other than not triggering a fault code? The only way to test the MAF is view live data, along with knowing what values are normal. Along the same lines, how old is the O2 sensor? Mixture is controlled primarily by MAF+O2.

As a very rough test, you could disconnect the MAF and go for a test drive. The engine may have a bit less power with MAF disconnected and it will trigger a fault code, but if engine temps drop dramatically, something may be fishy with the MAF. If there's no change in temps, the MAF may be ok. Again, live data would be more accurate. If you try this, clear the MAF fault code afterwards.



The harness replacement shouldn't have any effect unless something was done incorrectly, but I'd expect other problems besides high coolant temps. And the "cool harness" which runs the electric fans on high speed would just mask the problem slightly.

Hi fellow E500 Enthusiasts!

I have a 1995 E500 Limited with 74k KM. I had an issue with the MAF. Symptoms were very high CO readings, cutting out and hesitation. Diagnosis was faulty MAF PCB. While the MAF issue was present, engine was running mostly at normal and sometimes even at low temp. My explanation is that probably it was due to running very rich. I had the MAF replaced with a reconditioned unit and all issues of bad emissions, running poorly and cutting out are now solved. The engine now runs perfect and response is as it should be. Hot and cold start is also good now.

The issue I have now since replacing the MAF is that the engine is running too hot especially while under load/driving. The engine is continuously on 100 Deg. C and the temp. climbs to 105 Deg C. while driving 110-120 km/h. Once I reduce the speed or stop the temp. goes down again to 100 Deg. C. The electric fans are continuously on high speed. I can hear the fan clutch kicking in when accelerating but it does not change the temperature. I checked also while in idle/parking and temperature is on 100 Deg. C to accelerate to 2000-3000 RPM and hold it there. Fan clutch is engaging and electric fans are on high speed but temperature steadily climbs to 110 Deg. C. We do have high ambient temperatures here - was around 40 Deg. C with AC on.

The fan clutch has been replaced recently. Any idea what this could be? Radiator, water pump or thermostat? Would appreciate any help or inputs to troubleshoot this issue. I have heard that tase engines tend to run hot especially with high ambient temperatures but 105-110 Deg. C at a speed of 120 km/h does not seem normal.

Maybe someone has experienced something similar before. Thank you for your help.

@gsxr
Have mentioned the MAF issue in the first post of this thread quoted above. I tried to get a new MAF but none available and no luck anywhere. Purchased a used unit from a donor car in the UK and it turned out to be faulty. Luckily I got my money back. Did not want to take another gamble and bought a remanufactured/reconditioned unit from a company specializing in electronic parts like ECM's, ECU's and MAF's with one year warranty. Since changing the MAF, emissions (CO and HC readings) back to normal and no more stalling or hesitation.
O2 sensor has never been changed as long as I have the car which is many years. Do you suggest I change it?
Was just thinking maybe there could be a connection with the higher temps and the MAF as this problem was not there before. What I am suspecting though is that the faulty MAF causing the engine to run very rich and much cooler masked the temp. issue. I could be wrong though.
I will ask the workshop to carry out the MAF test as you suggested.

 

[IBNR]

Hello Gents...quick question about reading coolant temps on the oddly graduated and inconveniently labeled coolant temp gauge. Assuming we all agree that the gauge is reading exactly 100C in the first picture below, what would you call the reading in the second picture? 105C, more or less?

BTW, these pictures were both taken this afternoon, around 30 miles/45 minutes of driving apart, just loping along with traffic on my way home to Orlando from my initial visit with Pierre Hedary in Titusville; *not* a high-speed run by any means, I wouldn't even call it spirited. You can see the ambient temps as registered by the car's outside temp gauge, but those readings do not take into account today's truly hellish levels of humidity around here...the heat index this afternoon was near 100F if not above. Would these readings cause you any concern under such circumstances?

Thanks as always!

 

[gsxr]

Yes - the second picture indicates ~105°C. And the unmarked line is 100°C.

If this was with extended cruising at 65mph, it seems a little higher than I'd like, but not a cause for concern if temps normally remain under 100C in less miserable ambients.

 

[gerryvz]

I would say those are pretty normal temps for a high ambient and high humidity Southern US summer day, moving in traffic with full A/C on.

I personally have NEVER liked it when temps get above the 100C mark, but it’s an unfortunate reality with these cars with high ambient temps and is compounded by high humidity. They just DO NOT like hot and humid ambient temps.

The only thing I would do would be to test/listen/observe to make sure your low-speed fans are operating when the A/C is running, and that your high speed fans are running at the 107C mark.

For folks uncomfortable with temps shown much over 100C, a Cool Harness or equivalent homemade product set for say 102C could be an option.

It is frustrating because both with my M117 (560SEC) and M104 (G320) I can’t get them to go above 95C indicated.

In my opinion the biggest problem is the M119 fan clutch, which is not set properly. I would say that 90-95% of the people on this forum are running around with faulty fan clutches that are not kicking in early enough and doing their job.

 

[IBNR]

Dave and Gerry, thanks both. I did some digging on this and, following Dave's diagnostic trees for the AUX fans in other threads, discovered that the passenger-side fan wasn't running at all, under any circumstances. I gave it a few light taps with a screwdriver handle and it fired right up and now seems to be running just fine. I've also confirmed that the fans are correctly coming on at low and high speeds, so hopefully getting that second fan running again will help. Now I just have to figure out why I'm seeing a consistent loss of coolant in the expansion tank in fairly significant volumes without constantly finding big puddles on my garage floor!

 

[JC220]

Dave and Gerry, thanks both. I did some digging on this and, following Dave's diagnostic trees for the AUX fans in other threads, discovered that the passenger-side fan wasn't running at all, under any circumstances. I gave it a few light taps with a screwdriver handle and it fired right up and now seems to be running just fine. I've also confirmed that the fans are correctly coming on at low and high speeds, so hopefully getting that second fan running again will help. Now I just have to figure out why I'm seeing a consistent loss of coolant in the expansion tank in fairly significant volumes without constantly finding big puddles on my garage floor!

Probably a weak coolant cap which is leaking it off into the overflow reservior behind the fender.

 

[gerryvz]

It was interesting. I too was having to fill my coolant expansion tank from time to time, with a cup here, and a half-quart of coolant there.

Past engine oil analysis didn't show any coolant in the oil. No obvious external leaks, and no issues visually/externally with the Nissens radiator (which I'd replaced around 2012-2013).

When I did my top-end refresh job, and removed/reinstalled the intake manifold and gaskets, I have not had to add one drop of coolant, and I'm around 3,000 miles after the work. Everything is staying at the level of the seam in the expansion tank.

@IBNR -- when I very recently found that my low-speed fan wasn't working (when the A/C was running), I found the fuse in the relay was blown. After replacing that, the right-side fan didn't work. Touching it immediately engaged it, and it has been working fine ever since. So, I had the same issue as you. Mine was probably from non-use over a few years when I didn't realize that the fuse had blown and the fans weren't working.

 

[IBNR]

Probably a weak coolant cap which is leaking it off into the overflow reservior behind the fender.

Thanks, I'm really hoping that's the culprit. I have a new genuine MB cap on order, should be here in a few days. Fingers crossed!

Edited to ask: Does that overflow reservoir ever fill up and then leak and/or overflow itself?

 

[JC220]

Thanks, I'm really hoping that's the culprit. I have a new genuine MB cap on order, should be here in a few days. Fingers crossed!

I have personally observed one of my own m119 cars idling with an old coolant cap. Occasionally it would barf out some hot coolant into the reservoir. Then I wondered why it's coolant level was dipping

In that case nothing else was at fault all it needed was a new coolant cap and it was 100%.

This won't always be the case but when losing coolant it's highly advisable to ensure a good condition cap is on there it's a cheap part.

 

[gsxr]

Edited to ask: Does that overflow reservoir ever fill up and then leak and/or overflow itself?

Yes, the overflow reservoir will spill out onto the ground when it is full / overfull.

 

[JC220]

Yes, the overflow reservoir will spill out onto the ground when it is full / overfull.

View attachment 136649

If you want to test of this is your current leak - zip tie in a plastic bottle etc and run a temporary hose from the reservoir overflow into it. Take the car for a drive and let it idle fully up to temp for 15 mins or so then see if any coolant has collected in the test bottle

 

[Gullwing]

Did some more troubleshooting. A comparison between an ECM data stream and the temp. gauge reading shows no discrepancy. So the temp. gauge sensor and the gauge reading tally (see the images). Hence can rule out the temp. gauge sensor or the gauge itself.
Air temp. reading is fine as well as there will be some heat dissipated from the hot engine bay.
The MAF data stream is not supported on the scan tool so tested the car with another M119 MAF and it showed absolutely no difference.
So can rule the MAF out.
We do get an unknown fault code which appears sometimes when scanning. It says "32 Current" (see image). Don't think this points to anything.
Are now thinking it seems to be a water circulation issue. Now planning to inspect the aux. water pump and maybe open the main water pump and also check the thermostat again. Will also check the coolant lines to the aux. and heater.
The new ACM fan clutch seems to be churning out enough air.
Drove the car with aux. fans direct at continuous 2nd speed to rule out the fact that they may be cutting out while driving. It did not make any difference.
The temp. sometimes doesn't even drop at idle and other times it drops to around 90 Deg. C. and stays there. Strange behavior. There seems to be no consistency with the problem.
EZL is pulling enough vacuum. You can immediately notice the change if you pull off the vacuum at idle. Unless the EZL is doing something odd which could mess up the timing and cause hotter running.
Have ordered an OBD1 scan tool. Maybe this will tell us something.
Any thoughts or inputs you guys have are greatly appreciated.

 

[gsxr]

What scan tool are you using? HHT-WIN and Snap-On both will show MAF data. There are not many others which will show all the live data from the LH module (or any other computer modules). At least you were able to test with a different MAF.

The "32 current" fault code is due to the scan tool you are using, not being fully compatible with these OBD-1 systems. A hand-held blink code reader will give you most fault code info, but for serious diagnostics I'd consider investing in a Star Diagnostics (SDS) system that supports HHT-WIN (required for OBD-1).

The electric auxiliary coolant pump is only for the HVAC heater, it doesn't affect engine cooling.

Given that people have reported in the past receiving defecting new thermostats, it may not hurt to try another one, but I would be surprised if either a new t-stat or water pump made a difference.

I'm still a little suspicious about residue built up inside the engine block that could prevent thermal transfer, since a new radiator didn't help. But otherwise I'm at a loss.

 

[gerryvz]

I am no longer recommending Behr thermostats for M117/early M119 applications, nor M104 applications. Where possible, Wahler is a better bet.

 

[gsxr]

FWIW, the early M119 t-stat (116- part number) OEM is Behr. If you buy Genuine MB, it will be Behr in the package. Wahler is also available via aftermarket, although I don't know if one is any better. I see a Febi available which definitely should not be used.

Search for '116-200-03-15' | FCP Euro

parts online. Buy OEM & Genuine parts with a Lifetime Warranty, Free Shipping and Unlimited 365 Day Returns.

www.fcpeuro.com

Wahler is OEM for the later M119 t-stat (119- part number). Behr appears OOS at most vendors. Both early (116-) and late (119-) are silly priced at the dealer, $70/$80 respectively MSRP.

 

[JC220]

FWIW, the early M119 t-stat (116- part number) OEM is Behr. If you buy Genuine MB, it will be Behr in the package. Wahler is also available via aftermarket, although I don't know if one is any better. I see a Febi available which definitely should not be used.

Search for '116-200-03-15' | FCP Euro

parts online. Buy OEM & Genuine parts with a Lifetime Warranty, Free Shipping and Unlimited 365 Day Returns.

www.fcpeuro.com

Wahler is OEM for the later M119 t-stat (119- part number). Behr appears OOS at most vendors. Both early (116-) and late (119-) are silly priced at the dealer, $70/$80 respectively MSRP.



View attachment 136663

I personally have only every seen Wahler Branded MB m119 thermostats. Both early and late version although the recent early one was a NOS purchase so supplier could have changed.

In any case I always buy genuine MB thermostats there is so little to save its hardly worth the effort.

I do need to buy an M275 thermostat that is a whole different story. (Only MB and about 400bux)

 

[gerryvz]

My problem with Behr is only in recent years. I have had Behr M104 and M119 thermostats go bad after a very very short life. No issue yet, ever, with any Wahler.

 

[gsxr]

Joe, I've received OE / Genuine MB t-stats that were Behr for *early* M119, and Wahler for late M119. They may change suppliers so it's possible you received a Wahler early t-stat at some point, although usually MB adds a -64 suffix to the part number when there is a supplier change.

In the past I would buy OE but with the ridiculous price increase, I can't justify paying 3x for what is very likely to be an identical product.

 

[nocfn]

I just replaced a Behr Tstat with a Wahler. I installed this not long ago when I did the coolant flush and hose replacements but it was not impressing me. I suddenly saw temps (all sensors are new) pushing the 112-117 range while at idle in heavy traffic. Yes the feels like temp was 107 with gulf coast climate, and my fans were running ans was the fan. I just think I had a bad one.

So I drilled two holes as suggested by Jono in a new Wahler, stuck it in and replaced coolant. Went for a drive after the car got to temp and cycled thru defrost, heat and AC for 4 minutes each, added more coolant after cool down and did the process again. For now, things appear to be better than the last Tstat - now in the trash heap!

 

[Jlaa]

Just putting this here for comparison’s sake. Behr radiator, unmodified Behr thermostat (maybe I will modify next time) coolant hoses are all 3.5 years old, as is the ACM fan clutch.

First pic - gentle grade up for the past 5 miles, on the freeway after a full throttle blast with the AC cranked - 100F ambient, not humid, 100C coolant temp at 80mph.

Second pic - no more constant grade - lots of rolling hills so the car has had some time to relax going down as well as up … also slower speed …. AC still cranked - 98F ambient, approx 85C coolant temp at 50 mph.

BTW @TerryA this is in Mendocino National Forest neat Fort Bragg, which explains why the ambient temps are not

 

[gerryvz]

Those are completely normal and appropriate temperatures for the conditions. Exactly what I am seeing these days (though our summer ambients in Maryland tend to be more in the 91-95F range). Higher humidity may add a couple of degrees to those readings. But I too am not seeing any of my temps pass the 100C mark in the hottest ambients/highest humidity with the A/C running on high.

Looks good !

 

[Gullwing]

These are the readings I wish to see even though ambient temps are higher here

 

[gsxr]

@Jlaa, your numbers are perfect for those conditions.

Although Gullwing's ambient temps are higher, it still seems his engine temps are a bit higher than they should be. I don't get it. Are there other E500E owners in your area that you can compare engine temps with on a given day?

 

[TerryA]

Just putting this here for comparison’s sake. Behr radiator, unmodified Behr thermostat (maybe I will modify next time) coolant hoses are all 3.5 years old, as is the ACM fan clutch.

First pic - gentle grade up for the past 5 miles, on the freeway after a full throttle blast with the AC cranked - 100F ambient, not humid, 100C coolant temp at 80mph.

Second pic - no more constant grade - lots of rolling hills so the car has had some time to relax going down as well as up … also slower speed …. AC still cranked - 98F ambient, approx 85C coolant temp at 50 mph.

BTW @TerryA this is in Mendocino National Forest neat Fort Bragg, which explains why the ambient temps are not View attachment 136793 View attachment 136794

@Jlaa, Perfect Temps from what I see. Not sure I’ve seen that forest. I have been thru the Redwood forest just above or belo SF. Beautiful country up there. In the past I have driven PCH and 101 all the way up to Depot Bay Oregon. I great drive.

BTW, Knowing that your ACM fan has worked for 3-1/2 years is inspiring me to install my ACM fan that I bought about 3-1/2 years ago.

For what it’s worth due to health issues of having a painful hip and knee reducing my lack of enthusiasm, my 500E has been on sabbatical for about that same 3-1/2 years.

I now have newly rebuilt my own personal wheels (new hip & knee) and am getting ready to put my 500E back on the road. I have all of the top end hoses & fittings, VC gaskets, upper chain rails, new upper harness, the ACM fan and a lot of other stuff to install. Close to $1K in parts that I’ve purchased over time. I’m feeling better and it’s time to get started. Registration is due in September.

Just wish it would cool down a bit. It’s out there.

 

[Gullwing]

@gsxr
I have several friends who own E500's and they don't see temp. readings as high as mine in summer. Am receiving the OBD1 code reader in the next few days and am hoping this will shed some light on the issue and point us in some direction. Otherwise am puzzled and have reached a dead end.
Checked the vacuum lines to the EZL. They are fine. One line to the EGR was found defective and has been repaired. Drove the car with a MAF from another car. No impact at all. Checked ignition timing. Also in spec.
Removed thermostat and drove the car with distilled water only and no coolant for better thermal transfer. Also no change.
No symptoms of head gasket failure or water pump issues.

 

[gsxr]

I hope you didn't test drive with the thermostat completely removed - if so, don't do that again, it's not a simple 1-way valve as on other engines.