When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I was changing the oil recently on my C55 when I noticed that the coolant expansion tank appeared dark. When I opened it, it looked like a chocolate shake and when I rubbed the liquid between my fingers it felt greasy. I checked the oil I removed from the car and it did not appear to have any coolant in it and the oil filter looked normal. There was no condensation or anything on the oil cap. So I thought it could be the transmission fluid, so I checked the fluid with the transmission dip stick, which I bought a while back, and it appeared normal. My car has been running well, no smoke coming from the tail pipes, and no check engine light.
In doing some research I've come up with two possible issues. I could have a blown head gasket or the oil cooler could be leaking oil in to the coolant. Those are the only areas I can think of that the oil could come in to contact with the coolant.
Here's a little background on some of the recent repairs I've done to my car. I've changed the water pump because it was making a whining noise and as preventative maintenance. I had to change the seals on the oil cooler and oil filter housing because of an oil leak. I changed the radiator because it developed a leak on the plastic portion of the radiator. I drove the car a while like that before I discovered the leak, but I never let it over heat. I changed the expansion tank at the same time because it was falling apart and I did not want it to leak. After the radiator change I still had a gradual leak that turned in to a big leak. Turns out that a small, hard plastic coolant tube that runs through the firewall developed a hole. Once I replaced it, everything had been fine. I had refilled the radiator with distilled water until I could determine that there were no more leaks and it had been fine for the pass few months.
I'm thinking that maybe the car heated to the point that it created a small leak in the head gaskets or it could be the fact that I've been running distilled water only that ate away at the head gaskets or maybe it caused a hole in the oil cooler. I'm not too sure and I have not determined either of the issue. If anyone has any other ideas let me know.
I'll keep everyone updated regardless of the outcome so that maybe we can learn from this. My car is a 2005 C55 with about 150k miles.
Last edited by loudandheard; 01-06-2016 at 10:21 PM.
Could it be trans fluid? - if it's a Valeo radiator ... I would be suspecting of that. They were weak units in W203s. They are the same radiators as non AMG W203 bodied cars. Search the non-AMG section for a lot of information.
Could it be trans fluid? - if it's a Valeo radiator ... I would be suspecting of that. They were weak units in W203s. They are the same radiators as non AMG W203 bodied cars. Search the non-AMG section for a lot of information.
I installed a new radiator myself and it was a Valeo, but it was directly from Mercedes. It was the same brand as the original one I replaced. The build date on the radiator is 2014. Plus I checked the transmission fluid and it appeared fine. Also, I think it only affected early models, but I could be wrong.
Just wondering if you found out what was the issue there... I'm having the same issue and wanted ta have an idea of what I'm dealing with here... thanks!
Originally Posted by loudandheard
I was changing the oil recently on my C55 when I noticed that the coolant expansion tank appeared dark. When I opened it, it looked like a chocolate shake and when I rubbed the liquid between my fingers it felt greasy. I checked the oil I removed from the car and it did not appear to have any coolant in it and the oil filter looked normal. There was no condensation or anything on the oil cap. So I thought it could be the transmission fluid, so I checked the fluid with the transmission dip stick, which I bought a while back, and it appeared normal. My car has been running well, no smoke coming from the tail pipes, and no check engine light.
In doing some research I've come up with two possible issues. I could have a blown head gasket or the oil cooler could be leaking oil in to the coolant. Those are the only areas I can think of that the oil could come in to contact with the coolant.
Here's a little background on some of the recent repairs I've done to my car. I've changed the water pump because it was making a whining noise and as preventative maintenance. I had to change the seals on the oil cooler and oil filter housing because of an oil leak. I changed the radiator because it developed a leak on the plastic portion of the radiator. I drove the car a while like that before I discovered the leak, but I never let it over heat. I changed the expansion tank at the same time because it was falling apart and I did not want it to leak. After the radiator change I still had a gradual leak that turned in to a big leak. Turns out that a small, hard plastic coolant tube that runs through the firewall developed a hole. Once I replaced it, everything had been fine. I had refilled the radiator with distilled water until I could determine that there were no more leaks and it had been fine for the pass few months.
I'm thinking that maybe the car heated to the point that it created a small leak in the head gaskets or it could be the fact that I've been running distilled water only that ate away at the head gaskets or maybe it caused a hole in the oil cooler. I'm not too sure and I have not determined either of the issue. If anyone has any other ideas let me know.
I'll keep everyone updated regardless of the outcome so that maybe we can learn from this. My car is a 2005 C55 with about 150k miles.
there are some o-rings on the timing chain cover that can leak . both ways when the engine cools down you get a vacuum in the coolant and a small amount of oil can get sucked into cool .
01-06-2016, 10:11 PM
