rydberg
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- Jul 14, 2024
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- Your Mercedes
- E220 W212 OM651 722.646
Hi all,
I am new to this forum, and I am posting this because I have not found this problem described anywhere, and it is dire indeed.
Many people here probably know about the Valeo radiator issue present on models up to 2003. The glycol would mix with the ATF, resulting in catastrophic transmission failure. New radiators and cars equipped with external oil coolers have been considered safe in this regard. Until now, anyways.
I own a E220 CDI W212, built 2009. It is equipped with the 651.924 diesel engine and the reliable 722.646 transmission, approaching 30 years in the industry. This particular model has an external transmission cooler, at the front of the engine, mounted at the bottom of the bay, close to the radiator.
There are quite a few documented cases of leaking coolers, but leaks are relatively easy to find and fix. In my case, the cooler leaked internally, instead mixing the fluids. I have only found one reference to this problem, showing the issue quite clearly (
). The video is a couple of years old, but I imagine this problem is currently under development in a number of cars, so I thought I had better bring it up.
As you might have guessed by now, the consequences of not spotting this in time is a replacement of the whole transmission. The anti-freeze liquid will cause overheating and will wear down the clutches very quickly. My car is currently at the shop, waiting for a new (used) transmission.
So were there no signs, I hear you say? Alas, there were signs, but I managed to ignore them all. Here is a list, it might help someone with similar issues.
* A couple of times over a year, you get a coolant top-up message from the car.
You suspect a leak, maybe you bring it to the shop to have it fixed. Maybe you replace the water pump, thinking you have resolved the issue.
* The engine is showing tiredness under load
Going up a hill, you feel the engine not responding quite as normal. Maybe you suspect an issue with the compressor, or a vacuum leak. Maybe you find a small leak, and think perhaps you solved the issue.
* The cooler expansion tank looks odd
Now we are getting closer. Days before the failure, I noticed that the expansion tank appeared to have separated slightly at the middle seam. I made a mental note to have a look at that when I got the time.
* When checking the water level, you notice a faint amount of creamy substance on the cap
This is the certain tell that there is oil in the cooler system. At this point, the car should not be driven another inch. There is likely already a fair bit of contamination in the gearbox. The cooler needs to be replaced ASAP, and all fluids need to be thoroughly flushed. Even small amounts of coolant in the ATF will change its lubricating properties. My guess is that if the problem is fixed at this stage, the transmission can be saved.
Note that up to this point, there are no error codes, everything appears normal. So perhaps you disregard the issue for now, thinking how bad can it be?
* Running the car with a whole family in it, there is a sudden RPM increase, then back again
The gearbox is slipping, most likely due to the worn clutches. Pulling up the OBD2 codes in transit you may see P0710 or P0714, indicating an overheating transmission. The CEL is still not on, so you may be attempted to keep on driving.
* Half way through the journey home, there is a jerk during gear change and the CEL is lit. You pull up the codes and may find P1731 or P0730. The car goes into limp mode. By now, the contaminants, the incorrect ATF level and the high temperature is causing gear failures. There may be severe slippage. Faced with the prospect of towing the car, you may decide to limp home, after all that is what the mode is for, right?
Once home, opening the door, you feel the smell of the burnt transmission. Checking the engine, you see a definite separation along that expansion tank seam, and there is strawberry milkshake along it, maybe even along the side of the tank cap. At this point, the transmission is most likely gone.
As you can see, it is a quite a long list of indications, probably going back quite some time. People with more experience might catch on early and may be able to save the transmission. But many people will probably discover this too late, especially since the problem seems so rare and basically should not happen.
As for repairs, the cooler is replaced, the expansion tank replaced, coolant system flushed, pan dropped and cleaned, transmission flushed. In retrospect, the last step could have been skipped, but of course you hope for the best.
In any case, I hope this post helps bring awareness to this problem, and that it may need to be considered moving forward.
I am new to this forum, and I am posting this because I have not found this problem described anywhere, and it is dire indeed.
Many people here probably know about the Valeo radiator issue present on models up to 2003. The glycol would mix with the ATF, resulting in catastrophic transmission failure. New radiators and cars equipped with external oil coolers have been considered safe in this regard. Until now, anyways.
I own a E220 CDI W212, built 2009. It is equipped with the 651.924 diesel engine and the reliable 722.646 transmission, approaching 30 years in the industry. This particular model has an external transmission cooler, at the front of the engine, mounted at the bottom of the bay, close to the radiator.
There are quite a few documented cases of leaking coolers, but leaks are relatively easy to find and fix. In my case, the cooler leaked internally, instead mixing the fluids. I have only found one reference to this problem, showing the issue quite clearly (
As you might have guessed by now, the consequences of not spotting this in time is a replacement of the whole transmission. The anti-freeze liquid will cause overheating and will wear down the clutches very quickly. My car is currently at the shop, waiting for a new (used) transmission.
So were there no signs, I hear you say? Alas, there were signs, but I managed to ignore them all. Here is a list, it might help someone with similar issues.
* A couple of times over a year, you get a coolant top-up message from the car.
You suspect a leak, maybe you bring it to the shop to have it fixed. Maybe you replace the water pump, thinking you have resolved the issue.
* The engine is showing tiredness under load
Going up a hill, you feel the engine not responding quite as normal. Maybe you suspect an issue with the compressor, or a vacuum leak. Maybe you find a small leak, and think perhaps you solved the issue.
* The cooler expansion tank looks odd
Now we are getting closer. Days before the failure, I noticed that the expansion tank appeared to have separated slightly at the middle seam. I made a mental note to have a look at that when I got the time.
* When checking the water level, you notice a faint amount of creamy substance on the cap
This is the certain tell that there is oil in the cooler system. At this point, the car should not be driven another inch. There is likely already a fair bit of contamination in the gearbox. The cooler needs to be replaced ASAP, and all fluids need to be thoroughly flushed. Even small amounts of coolant in the ATF will change its lubricating properties. My guess is that if the problem is fixed at this stage, the transmission can be saved.
Note that up to this point, there are no error codes, everything appears normal. So perhaps you disregard the issue for now, thinking how bad can it be?
* Running the car with a whole family in it, there is a sudden RPM increase, then back again
The gearbox is slipping, most likely due to the worn clutches. Pulling up the OBD2 codes in transit you may see P0710 or P0714, indicating an overheating transmission. The CEL is still not on, so you may be attempted to keep on driving.
* Half way through the journey home, there is a jerk during gear change and the CEL is lit. You pull up the codes and may find P1731 or P0730. The car goes into limp mode. By now, the contaminants, the incorrect ATF level and the high temperature is causing gear failures. There may be severe slippage. Faced with the prospect of towing the car, you may decide to limp home, after all that is what the mode is for, right?
Once home, opening the door, you feel the smell of the burnt transmission. Checking the engine, you see a definite separation along that expansion tank seam, and there is strawberry milkshake along it, maybe even along the side of the tank cap. At this point, the transmission is most likely gone.
As you can see, it is a quite a long list of indications, probably going back quite some time. People with more experience might catch on early and may be able to save the transmission. But many people will probably discover this too late, especially since the problem seems so rare and basically should not happen.
As for repairs, the cooler is replaced, the expansion tank replaced, coolant system flushed, pan dropped and cleaned, transmission flushed. In retrospect, the last step could have been skipped, but of course you hope for the best.
In any case, I hope this post helps bring awareness to this problem, and that it may need to be considered moving forward.
