High Temperature Issue While Driving

[gsxr]

There's not a unit with a lower opening temp that I'm aware of. (Edit: There may be one, but I don't have photos or a part number, and I can't recall anyone posting details about this on the forum in the past 10+ years. As described below, this still should not have any effect on reducing temps of well over 100C.)

Please keep in mind that the t-stat should be fully open by 94°C. Since you are seeing temps of 105C+, a thermostat with lower opening temp would have zero effect.

I'm not familiar with the holes drilled to modify the thermostat - I don't know where they would be located, or if this will make ANY difference in function at 100C°+ temps.

 

[gerryvz]

I believe for many MB thermostats there were versions available that allowed the vehicle to run cooler. There definitely is for the M104 (I've seen the "cooler" version in MB literature) and I seem also to remember a cooler-running version for the late M117/M119 as well.

However, these cooler-running versions are designed for extreme environments (for example, if running in desert-type environments) and not for regular/ordinary motoring conditions.

In my opinion, they should never be used unless conditions warrant.

I will have to do some digging to find these cooler thermostat part numbers for the M117/M119 and M104 (they are different models of thermostat).



Behr made the part, 116 200 02 15 75, and I believe it was a 71C thermostat. It is permanently NLA.
EDIT -- this is for the early M116 and M117 engines, not the 5.6-liter later M117s, which share the same thermostat with most all M119s as found in the E500E.

Will keep digging......

 

[gsxr]

Gerry, the EPC is showing 116-200-02-16 as rated 84C...? And based on photos, that p/n won't fit the M119.

 

[Pat]

@Gullwing, based on a report in a different thread, have you confirmed that vacuum is present at the EZL? And when the vacuum hose is connected / disconnected, the idle speed changes briefly?

Someone else mentioned that engine temps dropped noticeably when this vacuum line was repaired, and the engine ran hot without the vacuum signal to the EZL.

I have low compression on two adjacent cylinders on my 1994 E420 with 140,000 miles. There is no white smoke or coolant/oil mix. After I replaced the fan clutch, I realized that engine temperatures never exceeded 100 whereas before the new fan clutch temps would creep above 100 to where the electric fans would come on and temps then slowly drop to below 100 and the electric fans would turn off. I put some of that head gasket sealant into the coolant and the car ran great for a few thousand miles but now it is back to running rough at all speeds.

I've convinced myself that there is a head gasket compression leak between these two cylinders. I've had the car since 2006 and temps have never gotten into the red but they have always triggered the electric fans to engage. I'm just about ready to pull the one head and replace the gaskets. The two adjacent low compression cylinders are at 100psi, the other six are all right around 180psi. Am I lost or does this sound like a reasonable approach.

 

[gsxr]

I have low compression on two adjacent cylinders on my 1994 E420 with 140,000 miles. There is no white smoke or coolant/oil mix. After I replaced the fan clutch, I realized that engine temperatures never exceeded 100 whereas before the new fan clutch temps would creep above 100 to where the electric fans would come on and temps then slowly drop to below 100 and the electric fans would turn off. I put some of that head gasket sealant into the coolant and the car ran great for a few thousand miles but now it is back to running rough at all speeds.

I've convinced myself that there is a head gasket compression leak between these two cylinders. I've had the car since 2006 and temps have never gotten into the red but they have always triggered the electric fans to engage. I'm just about ready to pull the one head and replace the gaskets. The two adjacent low compression cylinders are at 100psi, the other six are all right around 180psi. Am I lost or does this sound like a reasonable approach.

I'd do a leakdown test before pulling the heads (which is a major job). Verify the low compression isn't due to valvetrain or rings, which wouldn't be cured with new gaskets. However, if a sealant in the coolant helped for a short time, that does seem to imply a gasket problem.

That is a huge compression loss on the two cylinders, btw. I generally see 15-20 psi max difference from highest to lowest, 80psi would explain the rough running...

 

[Gullwing]

Hi Guys,

I am still fighting with the high temp. issue on my E500. The problem is still not solved. The issue is as follows. When driving slow below 90 km/h or in traffic and in idle the temp. stays normal. When driving above 90/100 km/h and the engine is under more load the temp. rises above the 100 Deg. C mark/line and climbs to 105-110 Deg. C. Once I slow down or am in traffic the temp. gradually drops down again. This with the help of the electric cooling fans at high speed. What has been done so far:

New radiator OEM
New fan clutch aftermarket ACM
New thermostat OEM
OEM water pump removed and inspected. Re-installed as found to be ok
Replaced MAF
Replaced Lambda sensor
Replaced all temp. sensors
New ETA/Throttle Body
New upper and lower engine wiring harness
Citric Acid flush
No faults with the OBD1 blink code reader

Several tests for head gasket failure turned out to be negative. EZL and control units still original. Another issue which I am not sure whether related or not came up. After a short drive and engine at operating temp. I switched off the engine to refuel. Then after re-start it was running very sluggish and rough like it was not running on all cylinders and there was no power. I drove to the next parking possibility and after re-start it was ok. This does not happen every time but this problem appears sometimes. Again no fault codes detected with the blink code reader after this issue.

From the emissions test we are reading a lean mixture on idle with practically nil CO and HC ppm after a hot run. Lambda around 1.1.
The on-off ratio using a duty cycle measurement at pin 14 on the x11/4 socket is averaging about 18%. Does that tell you guys anything?

In addition can the coolant flow through the heater circuit monovalve and the aux. pump have something to do with the issue? We noticed that on connections 3 & 4 of the monovalve, which we believe are the return lines from the heater, the temperature even with the heater on after a hot run was only 52 Deg. C measured with an IR thermometer.

Thank you guys for any inputs to solve the issue. Greatly appreciated.

 

[Gullwing]

@gsxr
Further to my previous post also noted the following: The E500 was parked for about 6 weeks with coolant level in the reservoir full and without being started. After starting, the warning light for low coolant came on. Checking the reservoir there was no coolant at all left in the reservoir. Empty.
No leaks detected anywhere and pressure tested the cooling system. No leaks. So am wondering if there was an air pocket in the system which after extensive parking disappeared causing all the coolant to flow from the reservoir into the radiator?
Today we noticed that the heating is also not working. So could there be an air pocket in the cooling/heating system causing all this?
Is there any method we can use to get rid of the air lock? Could the mono valve or aux. pump be causing an issue?

 

[gerryvz]

If the aux coolant pump is not working, that would ONLY be apparent during idle / standing. This is because the purpose of this pump is to continue to circulate a small amount of coolant through the heater core when the main water pump is running at very slow (idle) speeds.

The monovalve could indeed be an issue with regard to heat not coming on during operation of the vehicle.

 

[nocfn]

Air. Did the citric solution sit to long or could there be any residue mixing with the mew coolant/warer mix making the air lock?

edited for fat finger spelling issues

 

[gsxr]

Another issue which I am not sure whether related or not came up. After a short drive and engine at operating temp. I switched off the engine to refuel. Then after re-start it was running very sluggish and rough like it was not running on all cylinders and there was no power. I drove to the next parking possibility and after re-start it was ok. This does not happen every time but this problem appears sometimes. Again no fault codes detected with the blink code reader after this issue.

What you describe, particularly after a short drive & switching engine off, plus no blink codes, is 99.9999999% likely to be secondary ignition issues. VERY common. Almost guaranteed there was moisture in the cap after your short drive & shutdown, which caused several cylinders to misfire. While not related to your overheating issue, adding additional ventilation slots to the cap as described in this forum thread may cure that problem.

From the emissions test we are reading a lean mixture on idle with practically nil CO and HC ppm after a hot run. Lambda around 1.1.
The on-off ratio using a duty cycle measurement at pin 14 on the x11/4 socket is averaging about 18%. Does that tell you guys anything?

I don't speak duty cycle, but @jhodg5ck might know if this means anything significant.

In addition can the coolant flow through the heater circuit monovalve and the aux. pump have something to do with the issue? We noticed that on connections 3 & 4 of the monovalve, which we believe are the return lines from the heater, the temperature even with the heater on after a hot run was only 52 Deg. C measured with an IR thermometer.

Heater core flow should not affect cooling, assuming there is no air pocket in the system.

@gsxr
Further to my previous post also noted the following: The E500 was parked for about 6 weeks with coolant level in the reservoir full and without being started. After starting, the warning light for low coolant came on. Checking the reservoir there was no coolant at all left in the reservoir. Empty.
No leaks detected anywhere and pressure tested the cooling system. No leaks. So am wondering if there was an air pocket in the system which after extensive parking disappeared causing all the coolant to flow from the reservoir into the radiator?

This is not good. Either the system was never properly filled before (which seems unlikely), or it mysteriously lost a significant amount of coolant. If a vacuum filler is not available, fill the block through the upper radiator hose before topping off at the reservoir. When the t-stat opened after reaching operating temp, and heater working normally indicating the heater core is filled, the system may need another ~1 quart after cooling down. You'll need to properly fill the system and then monitor the level. If you lose more coolant without explanation, something really fishy is going on.

Today we noticed that the heating is also not working. So could there be an air pocket in the cooling/heating system causing all this?
Is there any method we can use to get rid of the air lock? Could the mono valve or aux. pump be causing an issue?

Heater not working, assuming the control panel & monovalve/duovalve are functioning, does mean an air pocket. Make sure the aux pump is working, drive the car with heater on MAX heat, with cooling system FULLY filled (at reservoir seam when cold), and the heater should work when engine temp exceeds 80C. If not, verify the climate control (pushbutton unit), mono/duovalve, and aux pump are all working and not blocking flow into the heater core.

The valve / aux pump should not cause the overheating problems, and would only affect heater operation inside the car.

 

[nocfn]

AIR

 

[Gullwing]

@gerryvz
@gsxr
@nocfn
@jhodg5ck

Hi Guys,

Thank you all for your inputs to solve my issue. Today we got another scanner so we managed to get some more data for troubleshooting.
Before we were only relying on the OBD1 blink code reader.
In the video below you can see the open loop duty cycle (on/off ratio)) measurement once warm at idle. What should this measurement be at for the M119/E500 once warmed up at idle? Does it point to a lean mixture which would explain the hot running?
With ignition on with coolant temp. low duty cycle measurement is at 30% which is the correct value as per spec. as far as we know. This data can be seen on the photo below among other readouts.
We are also suspecting the MAF as the reading has stayed on -0.10 kg/h when the car was running.
Disconnecting the MAF does prompt a fault code in the scanner. So the culprit could be the MAF or maybe the ECU is not interpreting the output from the MAF as it is supposed to.
The photos also show "No Fault" registered with the scanner which confirms what we got with the blink code reader.
We have also looked at the data of the ECU which is also below. The coolant temp. also matches what the temp. gauge is showing.
Any inputs would be great appreciated. Thanks!

 

[gsxr]

I don't trust the data shown by your digital scanner. Hot wire voltage should be around 1.20v at idle, increasing to 2-3 volts at higher RPM / airflow. 170v is not a valid reading. If the MAF was that far off, there should also be a fault code stored. Very odd.

Is there any way you can get access to SDS (Star Diagnostics) with HHT-Win support? Or buy a kit from AliExpress?

MAF readings in kg/hr (no load, revving with car parked) should be roughly:

Idle = 20kg
1000rpm = 30kg
2000rpm = 60kg
3000rpm = 90kg

Also, you can go for a test drive with the MAF disconnected and see if there is any significant change in operating temp. After the test drive, reconnect the MAF and clear the fault code.

 

[masayoshi]

I replaced the MAF because the data displayed by the X431 diagnostic machine was strange. So I bought a new MAF, but the result did not change. After that, I got STAR and examined it, and found that the data of X431 was strange. I recommend you to check it once with STAR.

 

[Gullwing]

@gsxr

Thank you for your post. We got some more data with regard to the afm as per below. Installed a Windows XP simulator to run the Star HHT but that needs to be perfected.
Anyway this was at idle closed loop engine warming up. Do you see any abnormalities?

 

[gsxr]

Nothing jumps out other than low battery voltage, if the engine was running.

Best to view data at operating temp, 80-90°C to eliminate any warm-up variables.

Again, a simple test is driving the car with MAF disconnected, if you haven't already done this... originally mentioned August 2021 but I don't see where you confirmed doing this?

 

[Gullwing]

@gsxr

We did the test drive with MAF disconnected some time ago. No change in temperature behavior.

Video below of live data with engine now fully warmed up. Do you guys notice any abnormalities?
Should the on/off ratio not be around 50%?
Have also added screenshots of air mass at different engine rpm.

Anxious to hear your comments/thoughts

 

[gsxr]

The air mass reading at idle seems high by ~50%, although ideally you'd compare to another M119.97x local to you and see if it has similar readings. I'd need to look at injection time as well and see if 3.8ms is normal at idle (can't recall offhand).

I don't usually pay attention to on/off ratio, I'm not sure what it means when your idle ratio is fluctuating between 7-15%. Dunno if that's normal, and if not normal, what it may indicate. @jhodg5ck / @Klink ??

 

[Gullwing]

The air mass reading at idle seems high by ~50%, although ideally you'd compare to another M119.97x local to you and see if it has similar readings. I'd need to look at injection time as well and see if 3.8ms is normal at idle (can't recall offhand).

I don't usually pay attention to on/off ratio, I'm not sure what it means when your idle ratio is fluctuating between 7-15%. Dunno if that's normal, and if not normal, what it may indicate. @jhodg5ck / @Klink ??

Thanks for your response. Air mass reading at idle is 33-35 with engine at operating temp. The air mass reading of 57 is at 1.500 rpm and 88 at 2.000 rpm

Regarding on/off ratio, I have seen live data of other cars where the on/off ratio reading was around 50% in idle at operating temp.
So not sure what spec is supposed to be.

 

[Gullwing]

@gsxr

An update: We have now tried another MAF and the temp. issue has improved. While driving between 100-120 km/h the highest reading we got on live data was 99 Deg. C. Before it used to climb to 105-110 Deg. C. So it stayed below the 100 deg. C line. This is however with the electric
cooling fans kicking in early on high speed due to the cooling harness.
The live data also confirmed air mass and on/off ratio readings to be in spec. Now the on/off ratio hovers around 50%.

One thing we still noticed though is that after a drive and the car parked......if we hold the rpm steady at 2.500-3.000 you can watch the temp. needle climb to over 100 deg. C to 105/110 deg. C. What could be the cause for this? The cooling fans are on high speed and we can hear the fan clutch. Is that maybe a fan clutch issue? It has been replaced with the ACM unit.

In addition we noticed that opening the coolant reservoir cap with fully cold engine the next day, there is still a small whoosh of air pressure however the coolant level is staying constant. Is this normal? Not a huge amount of pressure with coolant splashing out like before.
Again both leak down and dye test were negative.

 

[gsxr]

That sounds like a big improvement, temps staying under 100C. You could repeat the test without the electric fans running. The temp should be the same (under 100C) at only 120kph / 80mph.

At a steady 3000rpm and over 100°C coolant temp, is the mechanical / viscous fan roaring? If so, this means the clutch is engaged. The noise of the fan roaring is unmistakable and is much louder than the engine noise at 3000rpm. If the clutch is NOT engaged, that may be the reason for the abnormal temps at 3000rpm when parked.

With a cold engine there is normally zero pressure, but if it's a very low pressure, I wouldn't worry about it - as long as the coolant level remains constant (no coolant loss).

 

[Gullwing]

@gsxr

Hi Dave,

Very weird and odd development today: On a 50km test drive with exactly the same route, same ambient temperature and same way of driving as the previous two test drives, the temperature rose to 106 deg. C. We did not change anything compared to the last identical test drives where the temperature did not climb over the 100 deg. C line as reported. So now we are even more confused as to what could have changed.
Could it be an LH or MAF issue considering that we get different results every time we re-start? Or do you have any other ideas?
Seems the car has a mood of its own.

 

[gsxr]

That is bizarre. The LH will adapt to the change in inputs, so you can look at the adaptation values (low, high, idle) and see if any are significantly different, or far off from typical numbers. Also see if the on/off ratio is still around 50%. I'm definitely running low on ideas.

 

[Gullwing]

@gsxr

Hi Dave,

Thank you for the advice. We noticed from the live data that the idle on/off ratio now dropped again to between 20 and 30%.
So now we have swapped the LH thanks to a spare LH kindly supplied by @e500.org
We are now seeing an idle on/off ratio of around 50% again after the LH swap. So that is good.
Our original LH is 016 545 1432 and the replacement LH is 014 545 1832. Below is the data of the original and the replacement.
Seems the replacement LH is from an early W140 and it says LH whereas the original one says LH1.
Do you know if the replacement LH is compatible?
Tomorrow we are planning the same 50km test drive again and will see how it behaves. Fingers crossed.

 

[gsxr]

014-545-18-32 is an early LH module with WOT enrichment, and yes it is 100% compatible.

You'll need to look at live data to see the adaptation values. "Normal" is generally between 0.9000 and 1.0500, approximately, depending on the engine/LH combination. I've noticed that 1993-up engines with 1992 LH modules can trend slightly above 1.000 while "stock" combinations trend below 1.000. Screenshot below of my 1994 with 1992/WOT LH module, along with a video of live data from the same E500 you can use for reference:

 

[Gullwing]

@gsxr

Hi Dave,

Thank you very much for the helpful information. We noticed some unusual erratic behavior with our air mass readings today.
Please see video and air mass readings. The readings drop to 0 and also peak to 50. This sequence was continuous.
Any idea what could be causing this?

 

[gsxr]

I'm not sure what is causing the readings to oscillate. But I still do not trust your live data readings. Idle RPM when hot should be 650, not 750 - what is causing that? And idle MAF reading should be 18-20, not 27. If those values are correct, something is weird.

 

[Gullwing]

Hi Guys,

Does anyone have a source for the HHT software that runs on Windows 10 64 Bit?

 

[gsxr]

Does anyone have a source for the HHT software that runs on Windows 10 64 Bit?

@Jlaa, did you come across this in your SDS journey?

Gullwing, the easier solution is to use an older laptop (typically Dell D620/630) with an SDS software image designed for that specific hardware. I think there are SDS software images available for select IBM laptops and Panasonic Toughbooks as well. The software is often virus-laden so you don't want it running on a "good" laptop anyway, it's safer as a workshop-dedicated unit that is never connected to the internet. Bigger problem may be finding a good 38-pin cable, as Jlaa recently discovered with his SDS purchases...

 

[Gullwing]

Hi Guys,

Just wanted to give you an update. Replaced the LH and the temperature issue is still present.
We now got SDS HHT and video of live data is below. Have also attached a photo of the adaptation values
which seem to be in spec.
We are still having very low on/off ratio readings as you can see in the video of between 8-15%.
In all other live data videos I have seen, on/off ratio was around 50% which is as per spec. 50% (+/- 10%).
Any ideas what could be causing this? Both O2 sensor and MAF have been changed.

@gsxr

 

[gsxr]

I think you are on the right track with the on/off ratio but I'm not sure what would cause this, with new O2 and MAF.

Completely grasping at straws here, but has the crank sensor (CKP) at the rear of the engine been replaced? It's a rare failure mode, but sometimes those can cause really bizarre behavior related to mixture, with no fault codes stored. Relatively inexpensive gamble. I think a forum member posted here with details a few years ago.

EDIT - found the old thread where a faulty CKP resulted in wacky on/off (lambda) ratios:

SOLVED: Uneven idle, hesitating when accelerating, power is down (Faulty CKP) | Troubleshooting and Diagnostics

ADMIN EDIT: Final solution, after 1 full year of troubleshooting and replacing parts, was a defective crank sensor. The faulty CKP (crank sensor at rear of engine) was the root cause of the lambda (on/off ratio) malfunction and incorrect mixture. See post #76-#81 (link) for details. The title...

www.500eboard.co

 

[Gullwing]

@gsxr

Thank you of pointing us in the direction of the crank sensor (CKP) to be the possible cause. This is something we haven't looked at yet. Definitely worth a try.
We do have some odd and bizarre behavior with the MAF air mass. Please look at the air mass readings in the live data videos below.
Each video is with a different MAF and we have the same behavior. Unusual variations of air mass going down to 0 and up to 50. I shortened the videos to make them fit. It continues to fluctuate like that in the same way.
Any ideas what could be causing this?

 

[gsxr]

We do have some odd and bizarre behavior with the MAF air mass. Please look at the air mass readings in the live data videos below.
Each video is with a different MAF and we have the same behavior. Unusual variations of air mass going down to 0 and up to 50. I shortened the videos to make them fit. It continues to fluctuate like that in the same way.
Any ideas what could be causing this?

I've seen that behavior on some MAF's, and initially I thought they were defective, or in the process of failing. However the intermittent spikes of ±25kg/hr do not seem to affect engine operation, and if there is no fault code stored, the MAF may be ok.

That said, your second video shows the reading spiking up/down more frequently than I've seen personally. If you have a third good MAF to try it wouldn't hurt, but don't be surprised if there is no difference. The readings otherwise seem ok for the engine temp and RPM. I don't have any explanation for the variations, btw... @Klink?

 

[Gullwing]

@gsxr

We have tried another MAF and O2 sensor today. Please see videos of live data below. Now there was no more spiking of air mass up and down. It was more steady.
What has happened now though is that the O2 sensor voltage once warmed up got stuck at around 790 mV and did not oscillate and on/off ratio at 0%. Adaptation lower and upper 1.0004 and idle speed 0.0 kg/h.
Any idea what can be causing this?
Could the EGR have something to do with it? We found the purge valve to be defective. Was leaking. We blocked the line though.

 

[gsxr]

We have tried another MAF and O2 sensor today. Please see videos of live data below. Now there was no more spiking of air mass up and down. It was more steady.

The different MAF is causing the lack of spikes, which is fine, but the previous MAF may not be defective. It's still odd to me that you are seeing airflow readings of almost 30kg/hr at 80C and 650rpm. This is ~50% higher than I'd expect, but I don't know the root cause, and with 2 MAF's showing the same reading I don't think it's a bad MAF.

What has happened now though is that the O2 sensor voltage once warmed up got stuck at around 790 mV and did not oscillate and on/off ratio at 0%.

That isn't right. Are you using brand new O2 sensors? If so, what brand and part number? I doubt this is the problem, just curious...

Adaptation lower and upper 1.0004 and idle speed 0.0 kg/h.

Adaptation usually won't change until you drive the car for an hour or two, possibly with some shutoffs / restarts. Idling in the shop it will remain at the standard/mean values.

Any idea what can be causing this?

No, but I'd still replace the CKP with OEM (it's good preventive maintenance anyway). Zero fault codes stored, correct?

Could the EGR have something to do with it?

It's unlikely to be EGR related. If the EGR opens at idle, it causes a rough idle. You can perform this test with SDS activations, press a button and EGR activates & idle gets rough, press another button and EGR closes and idle should smooth out, etc.

We found the purge valve to be defective. Was leaking. We blocked the line though.

Good. One less item to worry about. If you haven't done a smoke test yet, I'd do that to verify there are zero vacuum leaks on the intake tract.

 

[Gullwing]

@gsxr

Thank you very much for the useful advice. Ordered an original CKP from Mercedes as well as the purge valve. Good news is that after installing the CKP we definitely have noticed an improvement in the air mass and on/off ratio readings.
Air mass is now more steady between 23-25 kg/h at idle whereas before it was much higher. On/off ratio while under load is around 50% now which is good compared to much lower values before.
On/off ratio at idle is between 27-35% which is still not quite at spec. (50% +/-10%) but still an improvement to before.
O2 sensor changed previously is new from Mercedes with part # 000-540-45-17. Now values are good.
Yes no fault codes stored.
We are still having intermittent air mass readings of 0 kg/h then peaking to 50 and then normalizing again. We had this with two different MAF's,
with one of them the variations are more frequent. Does this point to a faulty MAF or can we ignore this?
New purge valve is installed but we haven't connected it yet as we noticed charcoal powder in the old valve. Have ordered a new charcoal canister and will connect the new purge valve once we have replaced the canister.

 

[Alphasud40]

Gullwing I have to admire your perseverance. I tried my best to read all the threads so I missed something I apologize. Have you checked the intake path for leaks with a smoke machine? I was also thinking about your purge valve issue as I have had cars with a failed purge valve drive mixture/ and idle adaptions crazy. A stuck open purge valve can also be a source of hard starting poor running especially with high fuel levels. I am unfamiliar with this particular engine and the SDS system is there a throttle angle value at idle with this software? I’m hung up on the 750RPM. If throttle angle is low then suspect a vacuum leak. If it’s high then the LH wants it there for a input like A/C or coolant temperature.

 

[gsxr]

Thank you very much for the useful advice. Ordered an original CKP from Mercedes as well as the purge valve. Good news is that after installing the CKP we definitely have noticed an improvement in the air mass and on/off ratio readings.

Fantastic! I'm glad this worked - I don't understand why it worked, but this is at least the third different vehicle with a similar issue.

Air mass is now more steady between 23-25 kg/h at idle whereas before it was much higher. On/off ratio while under load is around 50% now which is good compared to much lower values before.
On/off ratio at idle is between 27-35% which is still not quite at spec. (50% +/-10%) but still an improvement to before.
O2 sensor changed previously is new from Mercedes with part # 000-540-45-17. Now values are good.
Yes no fault codes stored.

That sounds great. And, no fault codes matches what I saw on my car a couple years ago.

We are still having intermittent air mass readings of 0 kg/h then peaking to 50 and then normalizing again. We had this with two different MAFs,
with one of them the variations are more frequent. Does this point to a faulty MAF or can we ignore this?

I would ignore this. I've seen identical behavior on multiple MAF's that otherwise perform normally and are in vehicles that run & drive normally. You may see similar spikes at higher readings too, for example when holding RPM's at 3000 and reading ~90 kg/hr, you may see random jumps up or down by a fixed amount. The hot wire voltage may show similar spikes up/down that match the kg/hr readings. Sure would be nice to get a NOS / reman MAF but, well, thanks a lot Robert Bosch for NLA'ing them.

New purge valve is installed but we havent connected it yet as we noticed charcoal powder in the old valve. Have ordered a new charcoal canister and will connect the new purge valve once we have replaced the canister.

Smart moving waiting for the new canister. An old / failing canister that "leaks" carbon particles can clog and possibly ruin a new purge valve. For test purposes the valve can be completely disconnected / blocked at the intake side.

 

[gsxr]

I was also thinking about your purge valve issue as I have had cars with a failed purge valve drive mixture/ and idle adaptions crazy. A stuck open purge valve can also be a source of hard starting poor running especially with high fuel levels.

Yes - if the purge valve is stuck open, even partially, this can cause issues... and it is worse if stuck fully open. If the valve is stuck closed, you can just leave it alone.

 

[aliking]

Hello, i would like to know if the BEHR fan clutch is the reason of your problem, because i have spare one that im planning to change soon. Thank you

 

[TerryA]

Hello, i would like to know if the BEHR fan clutch is the reason of your problem, because i have spare one that im planning to change soon. Thank you

@aliking, Unless I missed something, in post #170 above @Gullwing said he used an ACM clutch. I am and others here are using ACM clutches and so far no complaints.

 

[aliking]

@aliking, Unless I missed something, in post #170 above @Gullwing said he used an ACM clutch. I am and others here are using ACM clutches and so far no complaints.

Yes Terry thank you, but i couldnt find any ACM it seems NLA, i wonder if anyone used the BEHR to know if its good or no

 

[Alphasud40]

I replaced the clutch on my 300E with the Behr/Hella unit. Worked like the OEM. The URO brand was a fail right out of the box.

 

[gerryvz]

I replaced the clutch on my 300E with the Behr/Hella unit. Worked like the OEM. The URO brand was a fail right out of the box.

You should do a search for “Tales of Woe” here on the forum if you want details on URO parts failures.

 

[Gullwing]

Hello, i would like to know if the BEHR fan clutch is the reason of your problem, because i have spare one that im planning to change soon. Thank you

Happy New Year! The Behr fan clutch was working fine and was not the cause of my issue. Since we were troubleshooting and to rule out the fan clutch we changed the Behr to an ACM.
I have been trying to source the original Sachs Horton but no luck so far.

 

[Gullwing]

Gullwing I have to admire your perseverance. I tried my best to read all the threads so I missed something I apologize. Have you checked the intake path for leaks with a smoke machine? I was also thinking about your purge valve issue as I have had cars with a failed purge valve drive mixture/ and idle adaptions crazy. A stuck open purge valve can also be a source of hard starting poor running especially with high fuel levels. I am unfamiliar with this particular engine and the SDS system is there a throttle angle value at idle with this software? I’m hung up on the 750RPM. If throttle angle is low then suspect a vacuum leak. If it’s high then the LH wants it there for a input like A/C or coolant temperature.

Thank you. Honestly I was on the verge of throwing in the towel on many occasions. If I wouldn't love the car as much I would have called it a day. Yes we checked the intake path for leaks. Purge valve and charcoal canister now changed. Yes there is a throttle angle value at idle and it is within spec.

 

[aliking]

Happy New Year! The Behr fan clutch was working fine and was not the cause of my issue. Since we were troubleshooting and to rule out the fan clutch we changed the Behr to an ACM.
I have been trying to source the original Sachs Horton but no luck so far.

Happy new year Gullwing, glad to hear that its good, i will use it in my car also, thank you again.

 

[gsxr]

You'll know if a clutch is not working. When fully engaged it sounds like a hurricane under the hood to at least 3500rpm (OE Sachs/Horton) or even higher RPM (all aftermarket). No hurricane = no clutch engagement. OE/OEM should be fully engaged by 100C coolant temp, but many aftermarket will be engaged at a much lower temp, sometimes under 80C. This isn't as great as you'd think, the noise gets irritating when ambient temps are low and the clutch doesn't need to be engaged...

 

[gsxr]

@Gullwing - any update on your cooling system woes?