Hello to all... Newbie here.

I am sending this post for my father. He has 1977 Mercedes Benz 450sel 4.5l (he said it was the small V8) that keeps overheating. He lives in queen creek AZ (maybe that’s why it keeps overheating. lol)
I am in the Army and I can’t help my father out except some internet leg work....

They have replaced the water pump, thermostat, clutch fan and reservoir tank, and the radiator rodded and flushed, and still no luck. It keeps overheating. They are thinking maybe a head gasket could be blown?? I told him he should try the reservoir cap and they r going to take the thermostat out and make sure it is not defective.
Does anyone have any suggestions on possible cause for the overheating? Any help would be greatly appreciated...


Thank you all for your help
SGTLARSEN

 

Car would have white smoke comming out of the exhaust if head gasket would be bad.
I would blaim faulty fan clutch. You should feel resistance when trying to spin the fan blades with cold engine. It would be like springing back effect if you try to spin it. If it is easy to spin, clutch is no good. Is the car running fine? I would have them check the exhaust for back pressure or flow restriction and timing for correct firing point.

 

Mbenz80,

Thanks for the info. Do you think we could have got a bad clutch fan? is that common? Could you put a Thermostat in backwards? would it go in the wrong way?

How do you bleed air out of the system? Is there a bleeder valve?

Thanks again

 

There is no bleader and on older cars like mine not even coolant reservoir, only radiator. There is two different types of cooling fan viscous clutches, maybe you got the wrong kind for your dad's car.
You can take the thermostat out and try it without it, car should not overheat but cabin heater will not work (not that he needs it in Az.).
Drop it into hot water and you should see the operation of it. Every one is stamped with opening temperature, yours should be 87 deg. C. Thermostat should be positioned with springs down and small weep hole with ratheling steel ball in it should be in the highest possible spot. Turn the thermostat in the housing untill this position is achieved.
Is your temp. gauge working properly? Is the radiator and evaporator clean without any air flow restriction?
I had overheating problem on my 1980 280SE at low speeds and traffic, after replacing thermostat (cheepest part of the system oem German Wahler for $8) it was the fan clutch. I've found one on local junk yard for $20.
Bad head gasket would pressurize your cooling system before warm up, it would be evident. To blead it, loosen up the highest positioned hose clamp of the whole system, fill up the radiator all the way, squeeze lower hose few times and crack the highest point opened just a little to let the air out. Ones coolent is flowing out, reconnect and retighten the hose.

 

Mbenz80,

Thanks you for all your help. Guess what it was the thermostat. They had originally replaced it, so either they put it in the wrong way or it was bad. So they waisted alot of money buying fan clutch, and having raiator rodded. But its all fixed now. Thanks again

 

check the fuel air ratio, it may be too lean.
check the oil viscosity... put in S.A.E. 30 or 40