Is 110°C too hot in 96°F ambient temps?

[gsxr]

Yup, your photos are showing the correct switch. Simply short the blades together without disconnecting (if possible), otherwise unplug the connectors and short the wires on the chassis side (brown / brown+blue with clear rectangular plastic cover over the female blades). You have these marked as "tails" with the lower blue arrows in your photo. With the ignition on (all lights on dash illuminated), the fans should turn on low speed when you short the tails together.

The red switch in your 3rd photo is exactly what you have on your car, it just looks different by itself, not attached to anything.

 

[msq]

will do.
(the 1st photo is my car, the 2nd photo I found on peach parts, the 3rd photo I found on the web somewhere).

If I short the wrong thing thing, since I don't want to ruin my interior, I'll just walk to the hospital.

 

[tomer]

I drove the ~65 miles back home from Dulles this morning. Ambient temps were 68-72F along the way. A couple of small stretches of stop and go traffic, but most of the trip I was moving along fine at speeds up to 90 MPH. The highest temp I saw on the way home was 100C indicated.

This is a photo on US-50, in Annapolis, just before the bridge over the Severn River. I was moving at a good clip, ambient 71F. Indicated temp was 91-92C with A/C on (center button pressed).

Honcho, you park that beauty at the airport??? Door dings!!!! oh the pain of that thought!!! lol

 

[msq]

Yup, your photos are showing the correct switch. Simply short the blades together without disconnecting (if possible), otherwise unplug the connectors and short the wires on the chassis side (brown / brown+blue with clear rectangular plastic cover over the female blades). You have these marked as "tails" with the lower blue arrows in your photo. With the ignition on (all lights on dash illuminated), the fans should turn on low speed when you short the tails together.

The red switch in your 3rd photo is exactly what you have on your car, it just looks different by itself, not attached to anything.

thanks @gsxr. So I was successfully able to short the fan and sure enough the Stage 1 of aux fan worked. I just pulled the protective plastic back and wrapped a paper clip (picture enclosed) and, as instructed, turned key so all dashboard lights were on and sure enough the stage 1 aux fan came on. I can see why you said "short the blades together without disconnecting (if possible)". Not a lot of room to fit hands in and play with connectors. When I was done, even something simple like sliding the plastic protectors back so they overlap, so no metal is exposed, was not easy.

So the stage 1 fan is good, the fuse is now good (it had been fried) so I guess if the stage 1 fan needs a certain ambient temp/AC-pressure I can wait until it gets hotter to see if it will kick on when AC is on (still in high 50's here and low 60's). I can also check the pressure in the system before that.

will report back.

thank you for all the help!

p.s. in the picture it looks like I let the paper clip touch the chassis, but it did not

 

[gerryvz]

Honcho, you park that beauty at the airport??? Door dings!!!! oh the pain of that thought!!! lol

I was on a very wide and end spot, Washington Dulles Daily Garage 1, Level 2, Row 2V, end spot closest to the terminal. Car was fine when I grabbed it today. I was partially parked in the end zone area, so at least 4 feet on driver’s side from the second car parked in the row.

 

[a777fan]

Msq,

Its been a while since I have done this, but if my memory serves me this might help:

- think of the red switch like a light switch you'd have in your house. As such, there is a power feed line coming in to the switch that is always ‘hot’. The other wire runs to whatever the switch controls, in this case the fan circuit. Instead of being actuated by someone manually flipping it as it would be in your house, the red switch uses the pressure from the AC to close the connection between the always ‘hot’ line and the fans.
- in order to test, all you have to do is disconnect the two ‘tails’ of the pressure switch, and then use a jumper wire to physically connect the end of the ‘hot’ wire to the wire that runs to the fans. In a sense you are ‘replacing’ the switch with a length of jumper wire.

Does that make sense?

Edit: oops, dave types faster than I, and it looks like you figured it out!! Yay!

 

[msq]

Thanks @a777fan. Yes, I did figure out the red switch short (with a lot of great help from @gsxr) and my stage 1 aux fan does work.
For a test today (70F ambient Temp) I let the car run on AC full fan for ~20 mins and the stage 1 aux fan still never came on (see attached pic of engine temp) and the car got pretty hot on a 70F day.
I hate to bring it to the dealer, but I may do that to have them check the refrigerant level, since maybe the pressure does not get high enough. I don't know if the pressure may not be high enough because its just not hot enough outside or if the car is low on refrigerant or maybe the red pressure switch is simply gone and pressure is fine.

The mechanical fan spins at a pretty good rate but per all the threads on this forum on fan clutch, that is hard problem to diagnose correctly. Additionally If fan clutch is a borderline problem and with the history on lack of reliability of new factory fan clutches not necessarily being calibrated correctly, you end up shooting in the dark......uuugh.

Interesting the temp gauge under the speedo showed 36.5C (~98F) when I left the car idling running for 20 mins with AC on, even though the outside temp is 70F. I wonder where the sensor for that is, but it must be affected by engine heat. I know that outside temp sensor is working since it has been accurate all along when driving the car.

 

[gerryvz]

The sensor for the ambient temp LCD sensor is located just behind the front license plate, and yes, when the car is not moving, it is/can be affected by engine heat.

 

[gsxr]

The sensor for the ambient temp LCD is affected by engine heat... however, as of 1988 models (09/97 production IIRC) the display has a speed input signal that will not allow the temp readings to increase while the car is stationary or moving at very low speeds, to avoid showing an inaccurately high reading. Full details are on page 3 and 4 of the FSM PDF, link below.

http://www.w124-zone.com/downloads/MB CD/W124/w124CD2/Program/Chassis/54-6320.pdf

Note that if you turn the ignition off / on, it will lose the stored "low" reading and show the "high" reading.

 

[gerryvz]

My 1989 560SEC is very definitely affected by engine heat. The sensor is in the same place as my E500's.

 

[gsxr]

My 1989 560SEC is very definitely affected by engine heat. The sensor is in the same place as my E500's.

I don't know if the 126 chassis had a temp display with the speed-based control as on 124's. Read the link in post #59 for details on how it works.

 

[a777fan]

Thanks @a777fan. Yes, I did figure out the red switch short (with a lot of great help from @gsxr) and my stage 1 aux fan does work.
For a test today (70F ambient Temp) I let the car run on AC full fan for ~20 mins and the stage 1 aux fan still never came on (see attached pic of engine temp) and the car got pretty hot on a 70F day.
I hate to bring it to the dealer, but I may do that to have them check the refrigerant level, since maybe the pressure does not get high enough. I don't know if the pressure may not be high enough because its just not hot enough outside or if the car is low on refrigerant or maybe the red pressure switch is simply gone and pressure is fine.

The mechanical fan spins at a pretty good rate but per all the threads on this forum on fan clutch, that is hard problem to diagnose correctly. Additionally If fan clutch is a borderline problem and with the history on lack of reliability of new factory fan clutches not necessarily being calibrated correctly, you end up shooting in the dark......uuugh.

Interesting the temp gauge under the speedo showed 36.5C (~98F) when I left the car idling running for 20 mins with AC on, even though the outside temp is 70F. I wonder where the sensor for that is, but it must be affected by engine heat. I know that outside temp sensor is working since it has been accurate all along when driving the car.

Side note: that is amazing oil pressure for that engine temp! Curious what weight oil you are using. Was that pic taken after just letting it idle? Or was it after a drive cycle?

 

[msq]

Side note: that is amazing oil pressure for that engine temp! Curious what weight oil you are using. Was that pic taken after just letting it idle? Or was it after a drive cycle?

Ha, very perceptive! The car had just been backed out of my garage and left idling 20 mins in my driveway and had not been driven in days (I have only had it out of storage two weeks). I had done a ton of preventative maintenance, as well as some deferred maintenance (e.g. wiring harnesses) while it was w/Jonathan at Blue Ridge for a few months. I also had all fluids in the car changed - everything brakes, transmission, cooling etc. and one of the things Jonathan recommended was "Oil Service/Brad Penn Racing w/ oil cooler" so thats what he did. I don't know the weight, but I can find out.

 

[Melville]

I believe Blue Ridge favors 20w50 Brad Penn. That’s what they put in my car.

Also, I think Brad Penn now goes by the name of PennGrade.

 

[gsxr]

Side note... coolant temps can be very different than engine oil temps. The oil temp may have been relatively low, especially if the car was not being driven. Idling doesn't put much heat into the oil (and almost zero heat into the tranny).

 

[gerryvz]

the name of PennGrade.

PennGrade One, actually.

https://penngrade.com/penngrade-1/

 

[tomer]

I was on a very wide and end spot, Washington Dulles Daily Garage 1, Level 2, Row 2V, end spot closest to the terminal. Car was fine when I grabbed it today. I was partially parked in the end zone area, so at least 4 feet on driver’s side from the second car parked in the row.

I should have known this was well planned!!! I have my kids fully educated on this concept as well, my daughter calls this type an "enda" space... I am parked in one today at work, like you said with about 4 feet separating me from the next vehicle... The "enda" is second only to the seldom seen and highly coveted "uni" spot!!

 

[gerryvz]

I was lucky to get an end spot. Trolled through that parking garage for a good 5 minutes before I happened upon it.... and it was very close to the new tunnel where you can walk underground from the parking garage to the Dulles main terminal.

 

[Trae]

Where is the single fuse for the 1992 located?

 

[gsxr]

Where is the single fuse for the 1992 located?

Trae, see the photo in the first post at this link:
https://www.500eboard.co/forums/index.php?threads/what-is-this-fuse-for.13195/

 

[msq]

I am dropping my car off at MB dealer for A/C evac and recharge to ensure system has enough pressure (now that I know fuse is ok since I replaced it and that stage 1 fan works via "shorting it" test). It seems really expensive (~$325). Normally I would have the really good MB independent do anything on my car, but he is booked two weeks out and I know MB will have all the right equipment for this service.
Even when this gets done I wonder "does it simply have to be hot enough/high enough ambient temp, independent of engine temp, for stage 1 aux fan to run?"
Separate, I had seen one of the previous threads on people removing their car from winter storage and having condensation in distributor, so I asked dealer "How much to remove distributor cap and check/wipe moisture and clean contacts, while it is in for the AC service" and the guys said ~2 hours which is $300. I have not worked on this car (or any of my cars) in a years, but 2 hours seems over the top, maybe there is something I don't understand. On my older cars I could pop distributor cap and clean/check and even replace for far less than that.

 

[Jlaa]

Separate, I had seen one of the previous threads on people removing their car from winter storage and having condensation in distributor, so I asked dealer "How much to remove distributor cap and check/wipe moisture and clean contacts, while it is in for the AC service" and the guys said ~2 hours which is $300. I have not worked on this car (or any of my cars) in a years, but 2 hours seems over the top, maybe there is something I don't understand. On my older cars I could pop distributor cap and clean/check and even replace for far less than that.

They are sandbagging / they are taking you for a ride. It could take 10 minutes or it could take HOURS if they strip the little fastener heads and have to resort to easy outs / dremeling a slot / JB welding a torx bit / etc. as referenced in a different thread current on the 500Eboard. It is likely that the dealership no longer has any techs that are familiar with these old w124 cars and they might be "learning once again" with yours.

If your car isn't stumbling, might I suggest either you (a) take off those caps yourself or (b) just wait until your MB independent has availability? It is not urgent.

 

[gsxr]

I am dropping my car off at MB dealer for A/C evacuees and recharge to ensure system has enough pressure (now that I know fuse is ok since I replaced it and that stage 1 fan works via "shorting it" test). It seems really expensive (~$325). Normally I would have the really good MB independent do anything on my car, but he is booked two weeks out and I know MB will have all the right equipment for this service.
Even when this gets done I wonder "does it simply have to be hot enough/high enough ambient temp, independent of engine temp, for stage 1 aux fan to run?"

I wouldn't recommend this unless the AC is not blowing cold. Again, if ambient temps are low, the pressure in the system is low (totally normal). You could end up being out $325 and have nothing change. Now, if they have a clue, they should connect gauges and measure the actual pressures to see if it's high enough to trigger the switch. If the switch is defective (possible, but not common) the system would need to be evacuated / recharged... and you sure don't want to pay for that twice!

Separate, I had seen one of the previous threads on people removing their car from winter storage and having condensation in distributor, so I asked dealer "How much to remove distributor cap and check/wipe moisture and clean contacts, while it is in for the AC service" and the guys said ~2 hours which is $300. I have not worked on this car (or any of my cars) in a years, but 2 hours seems over the top, maybe there is something I don't understand. On my older cars I could pop distributor cap and clean/check and even replace for far less than that.

Sounds like standard dealer quotes for an old car that nobody understands. Again, I would not even consider this unless you actually removed the car from winter storage and had misfiring problems. The vast majority of people on this forum have zero issues with condensation under any circumstances, including extended storage. Don't pay to fix problems that don't exist! Better yet, invest in metric Allen wrenches and check them yourself. Even for a first-timer it should be less than 1 hour.

 

[msq]

I wouldn't recommend this unless the AC is not blowing cold. Again, if ambient temps are low, the pressure in the system is low (totally normal). You could end up being out $325 and have nothing change. Now, if they have a clue, they should connect gauges and measure the actual pressures to see if it's high enough to trigger the switch. If the switch is defective (possible, but not common) the system would need to be evacuated / recharged... and you sure don't want to pay for that twice!



Sounds like standard dealer quotes for an old car that nobody understands. Again, I would not even consider this unless you actually removed the car from winter storage and had misfiring problems. The vast majority of people on this forum have zero issues with condensation under any circumstances, including extended storage. Don't pay to fix problems that don't exist! Better yet, invest in metric Allen wrenches and check them yourself. Even for a first-timer it should be less than 1 hour.

...I think I'll just ask them to measure the pressure. The system is blowing somewhat cold, but hard to tell since its such a typical warm spring day here in MA (42F ....).

....the car did run rough after I left it in storage from Jan - early May, and Jonathan thought it may be condensation, as it was running great when I got it from him. I then saw the others on the forum who had initial winter condensation problem.
After short period of it running rough, I let idle for about 15 mins twice then drove it a couple miles, let it sit and restarted and it has been great ever since so I suspect it was condensation from winter storage. Car runs great now.

...I think you're right, I'll just do it myself. I'll break out my 20 year old (now) rusty metric allen wrenches....it will take me longer to clean them up than it will to check the cap & contacts. I feel like if this was back when I worked on my own stuff this would take 30 mins (I just don't know how much stuff is in the way on the E500E's that I have to undo to get easy access, but I'll figure it out)

 

[northNH]

1¢: make sure your old allen wrench tips (ESP 3mm, and also 5) are good as new i.e. unworn, or replace them BEFORE having to start a how-to-remove-stripped-rotor-screws thread.

1¢: worth getting a Haynes 124 manual.

= my 2¢

 

[gsxr]

If removing distributor rotors, DO NOT use ball-end 3mm Allen wrenches. That alone should be adequate unless the bolt heads are buggered up.

The three 5mm heads on the caps are usually problem-free, even with ball-ends.

 

[msq]

1¢: make sure your old allen wrench tips (ESP 3mm, and also 5) are good as new i.e. unworn, or replace them BEFORE having to start a how-to-remove-stripped-rotor-screws thread.

1¢: worth getting a Haynes 124 manual.

= my 2¢

Yea, I have to get new allen wrenches anyway, last time I used them (for some non auto related thing) it wasn't worth the mess.

I saw the Haynes 124 manual, but it didn't look like it covers the E500E based on whats on the cover - maybe it does?
If not is there another "nearly as good" alternative.

 

[a777fan]

Yea, I have to get new allen wrenches anyway, last time I used them (for some non auto related thing) it wasn't worth the mess.

I saw the Haynes 124 manual, but it didn't look like it covers the E500E based on whats on the cover - maybe it does?
If not is there another "nearly as good" alternative.

Why use anything other than the factory FSM, which should be readily available to you as an active and contributing member of this site? *clicky clicky*

 

[gsxr]

The FSM is usually the best, but it's not written for DIY'ers... and doesn't cover "non sanctioned" work, lol. It's available several places free, including the official MB site (StarTekInfo). The "aftermarket" versions have a nicer HTML index courtesy of Steve Nervig; the OE index is Flash-based and pretty awful.

I think you are correct that the Haynes manual doesn't cover V8 engines. However, all of the other content (chassis, body, interior, etc) still applies. It can be a handy reference for certain jobs.

 

[gerryvz]

Savvy E500E owners use & implcitly trust the "E-Class Owner's Bible" as the authority.

https://www.amazon.com/Mercedes-Ben...Owner's+Bible&qid=1557926808&s=gateway&sr=8-1

 

[gsxr]

Savvy E500E owners use & implcitly trust the "E-Class Owner's Bible" as the authority.

https://www.amazon.com/Mercedes-Benz-Class-Owners-Bible-1986-1995/dp/0837602300/ref=sr_1_1?keywords=E-Class+Owner's+Bible&qid=1557926808&s=gateway&sr=8-1

Nice yank, Gerry. While that bible has some neat info, there were quite a few minor technical errors in the original printing. I doubt these were ever corrected. I picked one up shortly after release and it's collected dust on the shelf ever since. Neat trivia, but of limited use as a manual for anything, except some basic maintenance stuff. I'm not saying it isn't worth buying - just don't expect to use it to troubleshoot your M119 misfire after being parked 2+ weeks.

Oh, also, the M119 fan clutch mod described in there... we now know the root cause, and the mod is yet another Band-Aid. I think it also talked about a wiring mod that keeps low beams on with high beams, which is a no-no for multiple reasons. Be careful out there.

 

[gerryvz]

You're right....it was a

I haven't even picked up my own Owner's Bible for at least 15 years. I think it's in a box in my basement somewhere. Likely never to be found again.

 

[geraniumtr]

Dave & Gerry: Your comments on the usefulness of Stu Ritter's 'Bible' book seconded.

I would say that the trouble shooting section is quite comprehensive and helped me on a few occasions especially one time with a pesky door creaking issue.

Regards,

Peter Weissman

 

[msq]

Savvy E500E owners....

ok, you ruled me out with your first 3 words.
I am going to seek psychological counseling now for the blatant rejection, and will check into distributor caps after that

 

[msq]

ok, I got the car back from the dealer. The service advisor is actually a good guy and they have an MB Master Tech (he's been working on the MB's for 25+ years) at this dealer and he made sure he was on the car. As soon as I drove in the service advisor and master tech came out and the Master Tech said "never seen one of these" and I let him know they were never brought into the U.S.
No surprise @gsxr was right - coolant system was low on refrigerant (it had less than 1/2 the pressure that it should have) and they did evac & refill. It was blowing cold before (but was hard to tell on 42F day) now it really blows cold (it was 65F today and system had been evac & refilled). Funny enough when I got it home the stage 1 fan did not come on with A/C, but I am wondering now if its just not hot enough out (as gsxr mentioned)?(I know the fuse is good. I know when I short the stage 1 aux fan that works.....like a dummy I forgot to ask them to check the red pressure switch, since when they told me the car was low on refrigerant I assumed that was the issue with stage 1 aux fan.

A bunch of the people at the dealer were out checking the car out and the service advisor put a big "do not wash" black and white sign on the dashboard and told me "if we wash it, it won't look as good"

I am also wondering if fan clutch is ok (I know fan clutch is a weak point in these cooling systems) as when I let the car idle in my driveway with hood open and I was standing there listening all the sudden I heard a click/engagement type of sound and the mechanical fan sounded a bit louder.

 

[Jlaa]

@msq - is this you? If so, your car just got posted on reddit.

https://www.reddit.com/r/mercedes_benz/comments/bpbxum

 

[msq]

yes that is mine...not sure where they got the 1 of 100 number, I guess this is how rumors start, reddit....thanks for the heads up @Jlaa!

p.s. I just read the reddit thread.....$250K huh.....no, that is not the case, no clue where the person got that....although I am not planning ons selling it, $250K would get me thinking

 

[gsxr]

ok, I got the car back from the dealer. ... when I got it home the stage 1 fan did not come on with A/C, but I am wondering now if its just not hot enough out (as gsxr mentioned)?

Wait for ambient temps to get to at least 80F. If it's above 80F, and you are getting ice cold air out the vents, it's pretty likely the fans should be on. At this point you could also check yourself using gauges (easy to connect), a cheap R134a manifold gauge set is well under $100 and would allow you to diagnose at home. A name-brand gauge set would be a bit over $100.

I am also wondering if fan clutch is ok (I know fan clutch is a weak point in these cooling systems) as when I let the car idle in my driveway with hood open and I was standing there listening all the sudden I heard a click/engagement type of sound and the mechanical fan sounded a bit louder.

The click noise you heard should not have been the fan clutch. When the viscous fan clutch engages, there's not an audible clicking noise. The click could have been the AC compressor turning on or off (you can see this, if you watch the face of the compressor).

 

[msq]

thanks @gsxr will do on waiting for ambient temp. I suspect all is ok now that system is full and i know that fan works. Will also look into R134a manifold gauge set.

I am sure you are right that the clicking was AC Compressor engaging.

 

[msq]

@gsxr was right (no surprise). After vac & refill on A/C, today with ambient temp ~75F and the A/C on the stage 1 aux fan came on as designed and temp of car never got about 100C idling and driving it was probably in the high 80's and mid/low 90's. Net: Stage 1 aux fan works well and after replacing fuse and doing short test to make sure it works and an A/C service, everything works as it should and temp are in ranges expected during driving and idle.

 

[linjam]

I was on a very wide and end spot, Washington Dulles Daily Garage 1, Level 2, Row 2V, end spot closest to the terminal. Car was fine when I grabbed it today. I was partially parked in the end zone area, so at least 4 feet on driver’s side from the second car parked in the row.

That's just how I like to park mine

 

[linjam]

Last summer, I noticed my temperature gauge fluctuating in hot weather. Often it would get above 100 Celsius. I checked the forums here, which indicated below 90 should be average. My mechanic at Mercedes-Benz of Arlington said the three year old Genuine Mercedes fan clutch was pulling well, and the aux fans seemed fine. Everything else checked out fine. Very puzzling.

Last week in slow traffic on a 90 degree Fahrenheit day (first hot day of the year, at least that I was driving in) and with the A/C on, I took the below photo of the temp gauge. What??!! 112 degrees Celsius! I then checked out these forums and read that many had had problems with the Mercedes brand fan clutch.



I drove the car for a couple of days with NO A/C. In temps between 65 and 80 Fahrenheit, the temp stayed cool when on the highway or at least moving at a good speed but started to climb all the way up to 108 Celsius when stationary, at which point, it sounded like the aux fans would come on, and the temp would go back down to 100 Celsius or so.

I took the car back into MB of Arlington. The fan clutch, now 4 years old, worked well at first, but later was slipping badly. An intermittent problem of some sort. Further, one of the two aux fans was barely working. As the temp reached 107 Celsius, the aux fans would come on and pull the temp back down to around 100. I have ordered an ACM aftermarket fan clutch, new aux fans, and new fan shrouds. I will report back after they are installed.

 

[gerryvz]

Don't automatically assume it is the fan clutch, though it may well be. You should also consider replacing your thermostat. Reason being, a bad thermostat that is sticking closed, is going to be limiting the amount of coolant that is getting from the engine into the radiator for coolant.

Consider carefully the circumstances under which your temperature is climbing, irregardless of the ambient temperatures:

1) Is it climbing to hot temperatures under high speed running? Is it staying hot when running at high speeds, or does it cool down when airflow increases at high speeds?

2) Or is the temp climbing when sitting at stop lights and/or low speed running (as you seem to indicate above), and then drop down to cooler levels when the car is moving again? Or does it stay at the higher temps when you are moving again?

Having the A/C on is going to automatically raise the running temps 3-5C no matter what. I would say that on a hot day (80+F ambient temps) that anything up to and including 100C is pretty normal, particularly with the A/C on. Sitting at a stop light on a hot day, particularly a long light, I would not be surprised to see temps go up to 105+. This is just fine as long as they go down again either by the fans, or through motion adding airflow through the radiator.

Attached is a photo of my E500 running this past weekend on US-50, coming into Annapolis, about 6-7 miles west of the Chesapeake Bay Bridge. A/C was on when this photo was taken. This is a nice temperature for running. When I lived in Texas, with 95+ ambient temps with high humidity for months on end, temps of 105-115C were normal with the A/C on.

 

[gsxr]

My mechanic at Mercedes-Benz of Arlington said the three year old Genuine Mercedes fan clutch was pulling well, and the aux fans seemed fine. Everything else checked out fine. Very puzzling.

Last week in slow traffic on a 90 degree Fahrenheit day (first hot day of the year, at least that I was driving in) and with the A/C on, I took the below photo of the temp gauge. What??!! 112 degrees Celsius!

View attachment 83331

Your photo shows a temp of around 115-118°C. That is much higher than normal, for only 90C ambients, even if it's humid and the car is stationary.

I don't trust the mechanic's assessment that the current fan is "pulling well"... the vast majority of mechanics don't know how to tell good vs bad. As discussed in other threads, the clutch is an analog device, and varies infinitely between fully disengaged and fully engaged. Engagement is entirely based on AIR temp at the face of the clutch, not coolant temp. Obviously there are myriad variables which can affect this.

The ACM clutch is engaged almost all the time, so installing that will tell you pretty quickly if it was an airflow issue. Based on your description, it does sound like airflow, because when the electric fans turn on and/or the car is moving, the temps drop. If it were a bad t-stat or radiator, electric fans running would not help much; ditto for cruising at freeway speeds.

Side notes: If the t-stat is more than 7-10 years old, replacing proactively would be a good idea. If the radiator is original from 1992-ish, that wouldn't hurt either, but when it's removed to replace the electric fans+clutch, the radiator AND condenser should be cleaned thoroughly with compressed air. The OE twin electric fans are expensive; if you get ACM, the brackets from the original fans may need to be swapped to the new ACM motors. Also pressure test the cooling system and confirm it's tight to at least 1.2 bar; replace the cap if it isn't recent, ditto for the plastic reservoir if it's original.

And yes, the OE clutches are often mis-calibrated from the factory, which is ridiculous. If it turrns out your old clutch was bad, drop me a line if you want to sell it...

 

[Kyiv]

Last summer, I noticed my temperature gauge fluctuating in hot weather. Often it would get above 100 Celsius. I checked the forums here, which indicated below 90 should be average. My mechanic at Mercedes-Benz of Arlington said the three year old Genuine Mercedes fan clutch was pulling well, and the aux fans seemed fine. Everything else checked out fine. Very puzzling.

Last week in slow traffic on a 90 degree Fahrenheit day (first hot day of the year, at least that I was driving in) and with the A/C on, I took the below photo of the temp gauge. What??!! 112 degrees Celsius! I then checked out these forums and read that many had had problems with the Mercedes brand fan clutch.

View attachment 83331

I drove the car for a couple of days with NO A/C. In temps between 65 and 80 Fahrenheit, the temp stayed cool when on the highway or at least moving at a good speed but started to climb all the way up to 108 Celsius when stationary, at which point, it sounded like the aux fans would come on, and the temp would go back down to 100 Celsius or so.

I took the car back into MB of Arlington. The fan clutch, now 4 years old, worked well at first, but later was slipping badly. An intermittent problem of some sort. Further, one of the two aux fans was barely working. As the temp reached 107 Celsius, the aux fans would come on and pull the temp back down to around 100. I have ordered an ACM aftermarket fan clutch, new aux fans, and new fan shrouds. I will report back after they are installed.

I've driven on a totally shot factory clutch back from 1993 in the ultra dense traffic in Los Angeles for 4 years. Even going uphill in hollywood hills in a bumper-to-bumper traffic with multiple stop signs, in 95F, aux fans on their own would arrest coolant temperature at about 110-112C and bring it down fairly quickly

Also, once, in a fully loaded car in about 95F +/- ambient on several-miles-long uphill stretch of a freeway, at full throttle, going 85-95 mph., A/C on, I touched 115C briefly. On a shot fan-clutch with aux fans only

It very well could be that your abnormally high temperature is caused by the bad aux fan, with the underlying problem either a fan clutch or a thermostat. My ACM clutch solved my issue completely. Just today, 91F, highest I see when stopped in traffic is 95F, with A/C blasting. Highly recommend ACM clutch - cheap and works well

 

[Kyiv]

Gerry, your 500E needs an ACM fan clutch. You'll never see 110C in your car with it

 

[Melville]

I will let others with more knowledge correct me, but I'm not sure that a fan clutch that is engaged almost all the time is really that great. Yes, it means the engine stays cool, but an engaged clutch draws power. That is why MB designed a clutch that would engage when, and to the extent, needed to keep the engine within acceptable operating temperatures.

Also, an always-engaged clutch might reduce engine temps, but if the high engine temps were caused by anything other than a bad clutch, it is just masking another problem.

 

[gsxr]

I will let others with more knowledge correct me, but I'm not sure that a fan clutch that is engaged almost all the time is really that great. Yes, it means the engine stays cool, but an engaged clutch draws power. That is why MB designed a clutch that would engage when, and to the extent, needed to keep the engine within acceptable operating temperatures.

Correct. This is why I'm not a big fan [rimshot!] of ACM, mostly because I don't like the constant noise from the fan roaring. And it doesn't help power or economy either, but it does keep things cooler by eliminating airflow as a variable. I understand why some people prefer to just install ACM and sleep better.

Also, an always-engaged clutch might reduce engine temps, but if the high engine temps were caused by anything other than a bad clutch, it is just masking another problem.

If temps are still higher than normal with the ACM roaring, you definitely know the issue lies elsewhere!

 

[gerryvz]

As I said earlier, you have to very carefully examine and think about and reason the circumstances under which the temps are climbing (and diving, if they do). The circumstances will determine whether the radiator, water pump, fan clutch or thermostat (or some combination thereof) are the root cause of the issue.

 

[linjam]

Don't automatically assume it is the fan clutch, though it may well be. You should also consider replacing your thermostat. Reason being, a bad thermostat that is sticking closed, is going to be limiting the amount of coolant that is getting from the engine into the radiator for coolant.

Consider carefully the circumstances under which your temperature is climbing, irregardless of the ambient temperatures:

1) Is it climbing to hot temperatures under high speed running? Is it staying hot when running at high speeds, or does it cool down when airflow increases at high speeds?

2) Or is the temp climbing when sitting at stop lights and/or low speed running (as you seem to indicate above), and then drop down to cooler levels when the car is moving again? Or does it stay at the higher temps when you are moving again?

Having the A/C on is going to automatically raise the running temps 3-5C no matter what. I would say that on a hot day (80+F ambient temps) that anything up to and including 100C is pretty normal, particularly with the A/C on. Sitting at a stop light on a hot day, particularly a long light, I would not be surprised to see temps go up to 105+. This is just fine as long as they go down again either by the fans, or through motion adding airflow through the radiator.

Attached is a photo of my E500 running this past weekend on US-50, coming into Annapolis, about 6-7 miles west of the Chesapeake Bay Bridge. A/C was on when this photo was taken. This is a nice temperature for running. When I lived in Texas, with 95+ ambient temps with high humidity for months on end, temps of 105-115C were normal with the A/C on.

Thanks for your valuable input, Gerry. Much appreciated.

The radiator, condenser, and thermostat have all been replaced in the last 2-3 years, so that should eliminate them as possible culprits. My mechanic, Marv (he's the most old school mechanic at MB of Arlington and is the one most of the other guys go to when they need help) said the water pump was working normally.

Gerry, I'm no expert, but getting up to 115 Celsius, even in Houston summers, sounds pretty hot. I would think that level of heat would be hard on other components in the engine compartment as well, no?

In my case, the temperature would climb when moving slowly or not at all and would drop when moving more quickly. The night is was 65 Fahrenheit, this was the case, with the gauge reading between 108 and 82 Celsius -- pretty dramatic shift up and down, depending on vehicle motion or lack thereof.