Hello all,

Yes, most, if not almost all of the coolant inside the expansion tank leaked out from the cap after test driving for about 15 minutes with the AC on (Currently HOT here, about 102 deg).

Yesterday, I just finished some work on my 2002 C240. I was driving home few days ago when all of a sudden, the car had some hesitation and stalled on me and the CEL came on. I was able to start the car again and drive it home. Plugged the scanner and got a P0101 code. After searching the threads, I found DIY on MAF cleaning. So I went ahead and ordered parts from Autohaus and RMeuropean and replaced the following:

# 1120940604 Air filter
# 1121590080 Air Boot Seal Ring
# 1121590180 Air Intake Seal

I cleaned the whole Air Filter Housing, MAF (with CRC cleaner), elbow and throttle body (with CRC throttle body cleaner), replaced the air filter and the two seal rings. Everything went smooth, put everything back then drove the car. NO hesitation or stalling.

Now, when I got back and while in the process of deleting the P0101 code, I started smelling that hot coolant. I popped the hood open and there it is! The coolant is coming out from the cap of the expansion tank, sizzling! It seems like the pressure is pushing it out. I unscrewed the cap a little bit (with caution, of course) to let the pressure out. All it did was take more of the coolant out of the expansion tank. When I started the car again to park, I'm now getting a "Check Coolant Level" warning.

I realize that this may be a different issue that just happen to come out after working on something unrelated.

Recent work done:

Radiator: replaced 03/2015 @ 120K mi, hence new coolant.
Radiator Fan: replaced 05/2015 @ 121K mi.

The car is currently @ 122K mi.

I've searched and read threads relating to this issue and I'm coming to a conclusion that maybe the T-stat failed??? I started the car again this morning, plugged the scanner but I'm NOT getting any code.

Your thoughts and input are greatly appreciated. Thank you.

 

A thermostat that's stuck closed would easily cause your car to overheat. Because the coolant doesn't have as much room to circulate with a closed thermostat, pressure builds in the system, which I would assume is why coolant was leaking.

However to my knowledge, a failed thermostat should throw a code. Open or closed. I'd just order a new one if I were you. They're pretty cheap. And by pretty cheap I mean holy **** is this really a part for a mercedes? My god.

 

Get the Wahler they are identical with the MB logo defaced.

Did a shop do the radiator and why?
If they did do it take it back to them as it was not that long ago they should at least do a free quick diag to check it out.

 

Thanks Alswag and Trey.

I just placed an order for the Wahler T-stat and no kidding. This part is pretty "affordable". I ordered the belt too since it will be taken off anyway, might as well. I don't have much history on this car. I got it used. I already have the plugs and valve cover gaskets on stand by to be replaced, as soon as I can find the time.

The radiator I had done in a local shop. I was getting the low coolant level warning that prompted me to have it checked. I wanted to get it fixed right away and the local shop was pretty convenient at the time. I will bring it today at your suggestion Trey.

With the coolant leaking out, should I top it off? It's about a 15 minute drive to the local shop. Would there still be coolant within the circulating area? This is where I'm not familiar as to the coolant content/circulation and at this point not sure if there's any coolant left in the engine.

Thanks again!

 

I would refrain from driving it if at all possible as if coolant is not getting into the engine you could overheat it and do serious damage before you realized it. This is when AAA or a friend with AAA is very useful.
I would top it off with distilled water even if it is being thrown back out once it gets hot at least you know you tried. And if you choose to drive it split it up and let it cool down just to be sure. That said if you feel the water hoses starting to warm up then you know it is circulating you could also turn the heat on and see if it is blowing out hot air.

 

Sorry to say but could very well be a head gasket. Pressure from engine cylinder leaking into the cooling system which over pressurizes the system. When this is the case, one common thing to happen is coolant to 'overflow' several minutes after you come back from a drive and park it.

 

Mtnman, I hope that's not it!

At Trey's suggestion, I brought it back to the radiator shop 3 days ago. He did suggested to have the thermostat AND the expansion tank cap replaced (as was suggested by Rodney at benzworld forum as well).

So, the thermostat and expansion tank cap were replaced. Coolant was replenished and I have been driving the car since.

I have been checking for any blue/white smoke coming out from the back and none so far. The coolant have stopped leaking. I've been checking under the hood after my daily drive and observing the tank for any repeat leaking. None so far!!! I'll keep checking and update you guys in a few days.

THANK YOU for your inputs! Much appreciated.