OM601 Overheating at idle - PeachParts Mercedes-Benz Forum

mouramen · #1 05-28-2009, 03:48 PM

Need an opinion guys,

My car is overheating a bit, after 10 minutes of driving and than stop but leave the engine running, the fan engages (new 95ºC fan switch) and basically stays that way, for a moment it stops spinning but starts 3 seconds later.
This happens at idle, but if I accelerate the temperature decreases a bit and the fan desingages...
So, with higher engine RPM the engine cools down more easily.

What do u think? I'm thinking of a bad water pump!

Aprecciate you inputs!

scottmcphee · #2 05-28-2009, 03:54 PM

progressively was getting worse, or all of a sudden? (did the weather get hotter quite a bit)

check your coolant ratio first

mouramen · #3 05-28-2009, 04:52 PM

started doing this 3 or 4 months ago, now's getting worse cause this week the sun in frying us with 30+ºC...

LUVMBDiesels · #4 05-28-2009, 05:15 PM

Is the system full? It sounds to me like you have a big air pocket in the system somewhere. Make sure the system is full and there is no air then see how it performs...
I had a similar situation in both the BMW and the truck. I added coolant and burped the system and the issue went away.

JonL · #5 05-28-2009, 06:58 PM

Low coolant/air in system or slipping belt. Unlikely the water pump, though possible. (It would have to be eroded or the impeller would have to be slipping on the shaft.) Also check pressure cap.

mouramen · #6 05-28-2009, 08:35 PM

What's the best way to burp the system?

mouramen · #7 05-29-2009, 11:41 AM

More info!

Just noticed that the temperature was at 70 and the fan engaged, very strange...

One more thing, the coolant never leaves the expansion tank and the radiator is allways cool, maybe a stuck closed thermostat???

mouramen · #8 05-29-2009, 06:54 PM

Bump

dieseldiehard · #9 05-29-2009, 07:07 PM

Quote:

Originally Posted by mouramen

More info!

Just noticed that the temperature was at 70 and the fan engaged, very strange...

One more thing, the coolant never leaves the expansion tank and the radiator is allways cool, maybe a stuck closed thermostat???

The top of the radiator should be very very hot. perhaps its just that, a stuck thermostat. There were a few people who even experienced brand new thermostats that failed to open.

I would also add that there was a case where a water pump impellor was almost completely corroded away (eaten up?) on an OM603. gsxr had some ugly pictures of it. That would be the last thing that one expects but very hard to diagnose I think, perhaps by changing the water pump after everything else has been replaced.

JonL · #10 05-29-2009, 07:35 PM

Sticking thermostat, air in system might also give this symptom. There shouldn't be any obvious fluid motion in the expansion tank, just a small change in level depending on temperature.

mouramen · #11 05-30-2009, 11:35 AM

I think i'll just remove the thermostat and put it in a pot with water on the stove and see if it pops...

It'll be the 5th coolant flush this year...

If it turns out to be good then the next step will be problably the pump, i'll remove it and check the impeler and... one more flush...

JonL · #12 05-30-2009, 01:03 PM

It might be hard to tell if the thermostat is sticking by testing in a pot that way. You won't have a known good reference. Also, it is possible that the thermostat is physically deformed in a way that makes it stick when installed, but work perfectly when free.

I'd just stick a new thermostat in if you are going to open the system anyway. Then make sure you bleed it properly.

mouramen · #13 05-30-2009, 01:08 PM

What´s the best way to bleed the system?

I usually crank the engine, put heater at max, leave the expansion tank cap off and let it idle for 30 minutes...