Question about 1988 Mercedes-Benz 300

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Over heating Mercedes 300te 1988, Over heating on side of of radiator hot other side cold. How can I trouble shoot the water pump to see if the water is flowing through radiator?

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  • mdcaudle Apr 19, 2009

    Looking at the engine compartment on the right side of the radiator where top and bottom hose hook up, the tank is hot, on the left side where the over flow tant and the transmission oil cooler hook in is cold.

  • mdcaudle Apr 19, 2009

    Yes, that is the way the radiator is set up. the inlet is about half was down the tank and the outlet to the thermostat is on the top. The other side of the radiator goes to the heater system which hooks ur to the auxiliary water pump. The overflow tank hooks up at the top of the radiator on the inlet and outlet side. Which is on the right side looking into the engine compartment/

  • Roberta Smith
    Roberta Smith May 11, 2010

    first suspect would be the thermostat... if it is stuck closed water will not circulate and it will over heat.... feel the top radiator hose is it hot... careful of the fan when you do this

  • Roberta Smith
    Roberta Smith May 11, 2010

    from what you are saying .... your inlet and outlet hoses for your radiator are on the same side

  • Roberta Smith
    Roberta Smith May 11, 2010

    what side is hot ... the lower hose side or the upper hose side of the radiator ?



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Hello,seem your thermostat element maybe defective,if you change with new one,ask a lower degrees for early opening of thermostat element,ty

Posted on Apr 20, 2009


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Heatere core replacement

Be careful you dont over heat soon. I posted this in a different web sight I hope it helps you.

Re: Overheating and blowing cold air
I have been a mechanic for 20 years. Your problem is the heater core is plugged. The cold water from the radiator blows directly at the thermostat keeping it closed even when you are overheating! BAD DESIGN!! If you look at the water flow charts in AllData you will understand. If you rev the motor to 3,000 rpm's the turbulent HOT water at the water pump impeller (near the thermostat) will reach the thermostat to open it and the car's temp will fall very fast to the correct temperature. If you remove the thermostat it will not overheat but will run way to cold. If you bypass (loop) the heater core it will not over heat.

The hot water that leaves the heater core returns to the engine at the thermostat. It is the only hot water introduced to the thermostat to keep it open and allow the water to flow from and to the radiator. I normally just back wash the heater core and get large chunks of rust flake out then its fixed. Back wash then froward wash repeatedly many times. Also flush out the motor so you don't re plug the heater core. I hope you have now blown the head gaskets or cracked a head yet. Make sure to run the proper coolant in the car so you don't promote more rust flakes. And bleed the air out as mentioned in detail by other posters.

Nobody knows this little secret. Not even Subaru mechanics at the dealer, no TSB (Technical Service Bulletins a special note after the fact to mechanics). After days and days of trouble shooting a 1993 Subaru Impreza (2.0?) I looked at the water flow chart and then it was clear what was happening. This phantom overheating problem stumps the best mechanics and sends many Subarus to the crusher.

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2002 dodge 1500 Changed radiator, thermostat, and hoses. No heat

Why was radiator replaced?Did it have heat before ? If it was plugged, the heater core may also be plugged. Try flushing it with a water hose in both directions. I dont know why the botton radiator hose would be cold, the radiator should be a uniform temp and the air coming through the radiator should be HOT, when the engine is at operating temp. What condition was the old coolant? if it was rusty, the water pump may have lower flow than normal.

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1 Answer

Mercedes 300te, overheating

put alot of antifreeze on the radiator.this just happened to me last week and now it is fine
bet it cools a bit while driving NO? and than when you stop the gage goes up

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1 Answer

Runs hot

Your coolant level sensor has stopped working, my 93 olds regency is doing the same thing. You will need to goto the a Buick/GM dealership to get the part, it plugs into the side of the radiator.


am guessing you mean overheat. To "heat up" is normal. We want the car to heat up, but to go any higher than about 225 degrees would be to overheat, and that would be bad. If that is what you mean, then there are a number of things that could be causing it. It could be as simple as to high of a concentration of anti-freeze to water mixture(should be a bout 50%), to something as costlty as a blown head gasket. The water pump could have the impellers rusted off and not pumping, the radiator could be stopped up, there could be air trapped i the cooling system, there could be an obstruction to air flow in front of the radiator like leaves trapped in front of it, the cooling fan may not be working, even the thermostat you installed could be defective or installed backwards. It boils down to this: You either have a coolant flow or an air flow problem. (I am including the blown headgasket in the coolant flow catagory) As simple way to narrow it down is when then car is running hot, put your hand on the radiator. If the radiator is hot, then you probably have an air flow problem, see if the fan is working, or there are leaves in front of the radiator. If the radiator is cold, then you have a coolant flow problem, something is keeping coolant from flowwing into the radiator. (water pump, ai in the system, stopped up radiator, etc)
AS you changed the parts this maybe problem with the air flow in the car

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