94 w124 Overheating, Please Help
 

I have a problem with my 94 e320 that I can't figure out. About a month ago the car started to run hotter that normal when sitting still and the water pump made a small squeeking sound that you could hear with the hood open. The thermostat had been replaced about a year ago so I got a new water pump (MB) and after replacing it the problem got '"no better". Actually it got worse. The car started to run to hot while moving, which I figured the radiator was not flowing the way it should. The return hose from the radiator never seemed to get hot and the car has 225,000 so I figured it was time to replace the Radiator. I also felt a little play in the fan clutch.
So, after putting in a new radiator and a new fan clutch and a new water pump(ALL MB PARTS) and refilling the coolant at a 50/50 mix, the car is still not cooling. The heater gets hot and the aux fans come on when they should, but the temp keeps rising.
SO, I say to myself, should have just replaced the thermostat first to see if this was the problem. I take out the thermostat, just to see if that is the problem, it opens and closes in hot water, it is midnight and no where to get a new one so I put the car back togeather without it and refill the coolent and the problem is still there!!!! But now the heater dosent get hot and the motor temp still keeps rising. The return hose from the radiator also dosent seem the get very hot while the hose from the pump is very hot.
Please help!!! What else is there to keep the motor from cooling :confused:

I would recommend checking the sending unit for the temprature gauge. If you have replaced all these items the only other problem could be a blockage somewhere, but I would check the gauge. I have noticed my SL320 running hotter lately, but it is still within the operating range. I have replaced my water pump, thermo, and radiator. I was thinking about the fan clutch, but I am going to check the gauge first. I will let you know what I find.
Brian

First, if it only gets too hot in traffic, you need a new visco clutch, it's no longer working.

If it gets too hot on the highway, something else is wrong.

Your last problem is lack of coolant, these engines are a bear to get full of coolant. The cheap and cheerful way is to squeeze the upper radiator hose flat with one hand, then pinch the small hose from the rad to the reservoir tank shut, then release the radiator hose. This will pull coolant out of the tank into the engine and radiator. Repeat, keeping the tank full, until it won't take any more coolant, then start the engine with the cap off and the heater on full heat and add coolant as it sucks down out of the tank.

The correct method is to take the bleed plug out of the cylinder head (in the "sensor strip) next to the temperature sensors at the left front, on the M103, don't know where it is on the M104) and fill until it overflows, the re-install plug. Chancy, it IS an aluminum head and a steel screw....

You wil still need to add several quarts as the air works out of the head and heater core.

Peter

wow,
Thanks for the information, my 104 gets hot while in traffic. If I put it in neutral and then run the rpms up a bit it cools down. I guess that is my next purchase. Thanks and have a great day!
Best Regards.

Thanks for the replys so far, but the car was running hot moving over 30 or more mph and the system was full of coolant. Is there a mechanical sending unit of some kind before the water pump? The temp will still rise even after the aux fans come on.

No flow through the radiator sure sounds like a bad thermostat to me. Hard to check on this engine, though. Does the upper radiator hose get hot? Is the rad warm?

No, there is nothing between the water pump and cooling system that I know of.

One thing to check is cold pressure -- are the radiator hoses hard with the engine cold? this would mean a bad head gasket, I'm afraid.

Have you replaced the pressure cap? They tend to fail, and this will allow the coolant to boil in the head, causing high temps and cooling problems. Usually burps out a lot of coolant when stopping after highway runs if this is the case, though.

Peter

Any other suggestions?
 

I still can not figure out why this car wont cool.
Any other ideas would be great!!!!!
As I said, it has a new radiator, fan clutch, water pump and the thermostat is out untill monday when I will get a new one.
Anything other than a 44mag.!!!!!!!!!
Thanks, Dan

Do not drive it without the thermostat in place, it will seriously overheat. MB coolant systems require that the bypass orifice be closed by the plate on the rear of the thermostat to force water through the radiator. Without the orifice closed, the coolant will cycle around the block and head (and heater core) only.

Peter

Thanks for that info, the car is not moving out of the shop till I can figure this out.

Could it be the small electric water pump?

I don't know if a 94 still came with the small electric water pump, like the old 87 300E.

Well,
If you have replaced all those items, it would either be a defective head gasket or a bad sending unit for your temprature gauge, or a clogged cooling sleeve in the block or head. Good luck!

Try Bleeding the Air from the Cooling System
 

First buy a new expansion tank cap for $5.
Then, with car off, open the heater valve all the way. Remove the thermostat and leave the housing off. Open the expansion tank cap. With the car off, add coolant to the thermostat opening until full. Then add some more into the expansion tank until it runs out of the theromostat opening.

Reinstall the thermostat and housing cover. Start the car and let run for a few minutes, add some more coolant, if necessary. Put the cap on the expanion tank, and let the car heat up. If it gets too hot, run the heater full blast to keep it from overheating.

If it is still overheating, you must have a blockage or a blown headgasket.

Good Luck,

Charles

Solution? I have the same problem.
 

What was the solution? I am currently experiencing the same issues with my 1994 E320. I have replaced the radiator and am currently replacing the water pump (should finish this evening) and thermistat which was not in place. Before I invest any more time or money I would love to hear your findings.

The findings from that post are 3 years old..
If your car had NO thermostat, then that would cause your problem..the thermo has to be in there ...

It had an empty frame but the guts were out like someone was trying to find out why it was running hot.