OM601 temperature problem... or not...

[mouramen]

Hi guys,

w124 OM601 engine!

A wille back my merc started to heat a bit more than normal!
Now if I stop at idle after a trip for more then some minutes the car heats up and the fan only engages at this temperature - see attached pic!

Is this normal?? It started doing this a wille back! It scares the hell out of me!!!

I also noticed that the operating temperature droped a bit to near 80!

A question, how much is the temperature at the white line between 80 and 120?

Thanks in advance guys!!

[sixto]

That would be too hot for me unless you climb hills all day long. I'd start with a new thermostat.

We call the middle white line 100*C since it's between 80 and 120 even if not geomterically centered. 80 isn't geometrically centered between 40 and 120, either.

Check the archives for gsxr's posting on fan temp switch ratings by sensor color. Your mark is at about 105*C which is about where I'd expect the fan to kick in. I wouldn't worry about that if the fan works. I'd be more concerned that engine temp gets there at all without unusual load on the engine.

Sixto
87 300D

[mouramen]

Originally Posted by sixto

That would be too hot for me unless you climb hills all day long. I'd start with a new thermostat.

We call the middle white line 100*C since it's between 80 and 120 even if not geomterically centered. 80 isn't geometrically centered between 40 and 120, either.

Check the archives for gsxr's posting on fan temp switch ratings by sensor color. Your mark is at about 105*C which is about where I'd expect the fan to kick in. I wouldn't worry about that if the fan works. I'd be more concerned that engine temp gets there at all without unusual load on the engine.

Sixto
87 300D

Yeap, the temperature gets there always at idle, if I crank the car in the morning, after 10min at idle the temp gets there and the fan kicks in...

[sixto]

Overheating after 10 mintues of idling from a cold start? Could be a bad head gasket or cracked head if not a bad thermostat. Can you compress the upper radiator hose by hand at that point? Is there a rush of air out of the cooling system if you pull the cap 12 hours after shutting off the engine?

Sixto
87 300D

[mouramen]

Originally Posted by sixto

Overheating after 10 mintues of idling from a cold start? Could be a bad head gasket or cracked head if not a bad thermostat. Can you compress the upper radiator hose by hand at that point? Is there a rush of air out of the cooling system if you pull the cap 12 hours after shutting off the engine?

Sixto
87 300D

Ok, 12 hours after a 200Km trip I pulled the cap and no air came out of the expansion tank!

I have to see about the hose, should I be able to compress it?

[sixto]

It should resist with its rigidity, not with internal pressure like a properly inflated bicycle tire.

Sixto
87 300D

[mouramen]

I'll test the pressure inside the hose today, keep ya posted!

[charmalu]

Use a hand held infrared temperature gun, and check the temps at different locations around the engine.

hope you are something simple like a temp sensor or t-stat.

I pulled out my radiator one time and was amazed at how much crap was between it and the ac condensor. check for air flow.

Charlie

[mouramen]

New symptoms,

When cruising on the freeway in 4th (4 speed manual) and stepping on the accelerator the temp is about 85ºC, but if I take my foot of the pedal and put the car in neutral the temp increases a bit (5ºC maybe), it looks like that with less engine rotation the temperature increases. Can this be a bad water pump? I also listen to a uuuuuuuuu sound coming from the engine bay!

Could a bad water pump cause the "overheating" problems described in my first post?

[mouramen]

bump...

[tombance]

Well lets this about it logically. The only thing engine RPM affects is the water pump and the fan speed. At high speed and at 85-90C the fan shouldnt be engaged enough to play a part in the cooling at all, which would suggest it is your water pump.

Probably best to get it off and have a look. If it turns out fine all your out of pocket is a cheap gasket and then you wont have to do it again anytime soon.

Have you cleaned the radiator core? It could be plugged with dirt blocking airflow.