87 300TD,can't get it to stop running hot. - PeachParts Mercedes-Benz Forum

#1 08-09-2003, 03:17 AM

I bought this car on E-bay and hte moment I got it the temp would go up to 120 plus when there was a heavy load put on the engine(I live in the mountains).Shortly we learned that the head gasket was bad and the dealer we bought it from agreed to buy us a salvaged motor that is supposed to have 120000 miles on it.When the mechanic finally finished putting the motor in it still did the same thing.We did everything possible to the cooling system,short of a water pump and it still did the same thing.The mechanic said that his 300TD went up to 115 degrees and he thought the car was ok as long as it didn't go into the red.We drove the car about 2 weeks and then it fially went into the red,and blew it's head gasket .We figured that the engine we got must have had a bad gasket when we got it and went ahead and got the head gasket replaced and the car was still running hot on the mechanics first test drive.The mechanic says he dosn't no what it could be and we despartly need the car fixed on Monday(my wife is driving to Ohio),Please help,thanks.

speedy300Dturbo · #2 08-09-2003, 05:18 AM

Actually I'm thinking that the cylinder head itself is cracked. The motor on these 87's has a fragile cylinder head which is VERY prone to cracking when overheated.

haasman · #3 08-09-2003, 12:11 PM

Powerstroke

What a nightmare .... have you checked:

-The radiator for being hot all over. Idea here that possibly the radiator's internals are partially clogged. Use your hand (engine off) and check to make sure it is hot all over.

-Thermostat. Is it clogged or not opening fully?

-Coolant, what is your ratio in mixture? Certainly not more than 50/50 water to coolant ratio.

-Does your engine have an external oil cooler. Does this get really warm as well?

-Are all the coolant hoses getting really hot as well?

Have you posted in the Diesel Discussion Group

Keep us posted,

Haasman

MichaelW124 · #4 08-09-2003, 12:43 PM

Maybe the car you have had the engine head machined
while gaskets where replaced(several times before you bought the car ???) down to its limits and now as well when the gasket
was replaced. Can you measure the height of
the head in your engine to see if is within limits-
maybe somoene who has the same engine here online can
measure theirs and you can compare .
Previously I had a 190E mercedes and they machined
the head by 3mm way beyond "normal" which caused etxtreme pressure increase and constant damage to the main gasket.
Michael, Poland

psfred · #5 08-09-2003, 03:16 PM

Running at the mark between 80C and the red zone is normal in heavy traffic, sitting with the AC on. Otherwise, you shouldn't get that hot.

What have you replaced in the cooling system?

Coolant tank cap? These do go bad and will cuase overheating since the coolant will boil at about 120C.

Radiator -- aluminum, they only last so long, and tend to fill up with corrosion, limiting cooling capacity. It's worst in a circle that matches the fan.

Bad radiator hoses -- lower one can collapse under load, reducing coolant flow.

Bad thermostat (very common), won't open or close fully, so you run hot when it's warm out, cold when it's not.

And so forth.

Peter

#6 08-10-2003, 12:21 AM

We've changed the radiator,all the hoses,the cap,sensors,fan clutch and nothing seems to help.The head was checked for cracks at the machine shop and nothing was seen.The tempature is not affected by the a/c since is not working.It is possible the head has been overmachined bit the engine is only supposed to have 120,000 miles.Can anyone help?

MichaelW124 · #7 08-10-2003, 02:36 AM

question/suggestion: open the engine coolant reservoir.
Turn the engine on, add some water to fill it above the fill line
so that it spils over the top of the reservoir, look at the
fluid. Have somoene step on the gas pedal while
the other person looks at the fluid. Are there air bubbles
coming out from the fluid? Try this several times with a cold
engine. If there are air bubbles coming out than it means
that the engine coolant is emerging from your cooling system
either in the engine or elswhere.
ALSO you might want to replace the thermostat-not the housing
just the thermostat. Is your heater working properly-do you
smell engine coolant in the cabin?