Mechanics

MY CAR TEMPERATURE KEEPS REACHING 120 DEGREES CELSIUS

1987 Mercedes Benz 300e • 120,000 miles

Temp gauge is close to the red zone. What can be the problem and the solution? I have replaced the radiator, fan clutch, thermostat. My auxiliary fan comes on at around 105 degrees Celsius but my temperature still doesn't drop. I was told that the car has to run at 90-95 degrees Celsius. When I accelerate the car when stopped, the temperature drops a little bit. The temperature increases the most when it is in idle.
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Scarfaze
September 29, 2011.




You might try a new radiator cap as they tend to go bad. You could have an internal engineprobalem as well causing this. You canalso get some coolant additive that will allow theengine torun coooler, it works pretty well. You also might have a water pump problem.


Hmac300
Sep 29, 2011.
I don't think its the cap because there is no leakage of coolant through the cap and the water does not boil. Also I put special Mercedes Benz antifreeze I think its g-05 and there is absolutely no difference. I already removed the water pump once and I noticed that the impeller was like brown in rust but the bearing is good and the impeller would move with no problem. When the car is running I touch the return hose and you can feel the water pressure and how hot the water is. The odd thing is that it doesn't overheat right away it takes a while, and it mostly happens when i'm idle. P.S: Thanks for the info. I really appreciate it.


Tiny
Scarfaze
Sep 29, 2011.
Radiator caps go bad because they won't hold the pressure that they are required to. Not because they leak. Any mechanic with a pressure tester or maybe an auto parts store can test to see if it is holding the correct pressure. If a cap doesnt' hold the correct pressure it causes a system to start to overheat or run hot.


Hmac300
Sep 29, 2011.
Alright. I will check it. Let me ask you one more question. When a car overheats will the water boil or are there cases that it wont? Because I noticed when the temperature in the car reaches a high level the water doesn't boil.


Tiny
Scarfaze
Sep 29, 2011.
That is why there is a radiator cap, it pressurizes the system so as the temp goes up it has to go higher due to pressurization. With normal water boiling at 212 with a 15# cap it woldn't boil until about 245 degreesF. Ha this car been checked for a possible head gasket leak?


Hmac300
Sep 29, 2011.
Yes. There is no head gasket leak because there is no oil in coolant. And coolant smells normal. And if there was a head gasket leak my car would overheat a lot faster due to the fact that the oil is hot it would just heat up my engine even more. The overheating is not that serious because while I rev and drive the car the temp goes down. Ive repaired the whole cooling system myself. The only thing I havent replaced was the water pump because I saw the bearing was fine and the impeller was spinning well. I would have to test the cap but I checked it and it looked fine. The gasket was perfect and I would squeeze the spring and when I would let go it would return back to the original position.


Tiny
Scarfaze
Sep 29, 2011.
I would consider having the radiator core tubes cleaned, a back flush is not good enough, the radiator core is made up of rows of tubes and they are all joined by the top and bottom tanks, so if say 20% of the tubes are blocked you will still get flow through the radiator but at a reduced rate and this can cause over heating, I would look at this.


Mhpautos
Sep 30, 2011.
It's a brand new radiator. I got it last week actually. I will have to look into the radiator cap and the water pump. Thanks for all your help I really do appreciate it.
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Tiny
Scarfaze
Sep 30, 2011.
I replaced the radiator cap and there is no difference. I did a self inspection of the engine when the temp gauge reads hot and I noticed that the car wasn't overheating. I actually touched the radiator cap with my bare hands and it wasn't hot it was warm. I also got a second opinion from a mechanic and he said that the water isnt boiling and the engine isnt overheating, but yet the temp gauge on the dash reads that the engine is overheating. Any ideas?


Tiny
Scarfaze
Oct 3, 2011.
First does this have the silicone filled clutch fan or is it a flex fan. The clutch fan may be bad and not working at idle an dlower speeds when it is supposed to. The flex fan should flatten out when you reve it. You could also try replacing the coolant sender, pic inclosed.


Hmac300
Oct 3, 2011.

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