MeInQ8

I took it to a radiator specialist since I have this bad radiator water smell and every 10 days or so the car display check coolant level "it needs about 1/2 to 3/4L of water" so replaced that old dirty water but they said no radiator issues but still check with a mechanic it could be a hose issue somewhere else. I took it to a mechanic no leaks from the front or under BUT he found it raining water from behind the motor dripping on the exhaust when he lifted it. He unscrewed a small plastic short hose something from behind the motor, cleaned it up, added an extra rubber to it and he said I should be good and he also said it’s a common issue with the CLKs.
The smell is much lesser now but I still have the same issue so I thought it could be the water reservoir plastic cap so I got a new one from the dealer but again no luck it still need water?

DanielFD

Testing water leaks can be tricky. The mechanic is right in the back of the engine towards the top there is a hose that either breaks or the seal deteriorates and water will leak and its common. The correct way to diagnose the issue is by pressuring the coolant system using a small hand pump that's installed in place of the cap of the expansion reservoir, then you search for leaks which should be pretty obvious to find.

Rudeney

A bad reservoir cap is a common source of coolant leaks. Another is the water pump. It can leak and the movement of its pulley and belt will sling the coolant away so there is no wet spot. You might remove the pulley and look behind it to see if there are any signs of coolant leaks.

MeInQ8

Checked the water reservoir no leak and I got a new cap but still every 7 to ten day it needs 3/4L of water. How easy is to check the water pump pulley?

Rudeney

Remove the belt, then remove the pulley (4 bolts hold it in place, 13Nm). You may need to remove the "wide-band silencer" from the intake duct if it's in the way.

MeInQ8

Thanks...
I was about to check the pump but then yesterday I found oil in the water reservoir "beige/tan color" took it to couple of mechanics/radiator specialists some said motor and some said transmission. Last shop said transmission oil 99% because of the water color and the texture so they replaced the radiator and cleaned up the oil 80% of it, they even added some soap to the water in it now and they said come back in a week for a second clean up.

The shop advised to replaced the motor color because 100% when the transmission cooler goes bad the motor cooler goes bad as well in couple of days?

DanielFD

I'd make sure you have the valeo radiator first then it will most probably be your radiator, but you should be feeling a lot of weird things from your trans by now. If that's not the case, I noticed you have a CLK200 which means its not a US model car which means most of them are equipped with oil coolers. Mercedes's Oil coolers are notorious for leaking oil into the coolant, I'd check that first, if you have one its most probably shot. Exactly what do they mean by Transmission Oil Cooler?? Unless I've never heard of that its most probably the radiator they are talking about, in that case the motor oil cooler and radiator are not related at all.

DanielFD

ugh i apologize for the hyperlinks.. i have no idea how they got there..

MeInQ8

Tired of repairs, I'm about to sell it : ) I was told that the motor oil cooler isn't easy to get to it to check/replace...but I see no issues with the transmission, the car drives normal. It's dark now but I just checked with the water reservoir I saw a little less water in it and some of that light tan color still but I will check back in the AM. I was told that to have a 100% clean water it may take two or three full cleaning to have a clean water again.
Thanks!!

DanielFD

Interesting.. I had an old 1989 XJ6 Daimler had tons of oil in the coolant, didn't have the space or tools then so i just kept poring water into the coolant expansion box until all i could get was clear water and repeated for about a week everyday. I dont know about the CLK200 engine but if its anything like the C230 kompressor m271 (if i'm not mistaken its the same engine, just smaller supercharger) those engines are a handful when it comes to repairs, i eventually got rid of it. The M112 (clk320) is just gold compared to that engine. Engine cooler is really simple to reach on the M112 btw. I'd look into replacing the Motor oil cooler see if that fixes your problem, and since your loosing water open up the engine oil cap you should see some tan color there or on the cap itself then you'll know for sure its the engine oil cooler.

MeInQ8

Ohh..then maybe I will wait a week or so I can do more cleaning for the water to clear up. I see no tan color on the cap or inside I waited couple of min when I shut the car off. Is there is a better way to check because the oil cooler job is about $250 total you know : )
Thanks

DanielFD

mmm we'll i'm not sure about this but maybe the glycol test that they use on the trans oil to check for water will work on the motor oil..

MeInQ8

The other day I noticed mix oil/water in on the motor right on the oil cap also lots oil in the coolant reservoir as well. I Took it to a garage to check it...They are running diagnosis because they suspected a head gasket and it will cost $$$

DanielFD

gaskets rarely fail especially since your car isn't so old. Make sure they check the motor oil cooler. 99% of the times its just the motor oil cooler like we discussed before.

MeInQ8

They said the motor oil cooler will pass oil to the radiator but not coolant to the engine?

DanielFD

That is not correct. It is directly related to both oil in the radiator and water in the oil. I say this from experience, friend is an Indy mechanic and has changed out as many oil coolers as the amount of hair on his head.