M104 running 100C
 

Hello

Water pump was leaking,replaced WP and thermostat 87C with Zerex G-o5 coolant.
Now the temp. stays at the 100C mark before it was staying just past the 80C mark the old thermostat was 87C. I drove the car around let it idle for 1hr. with heat running before it went to the 100C mark in summer time stop and go traffic. It's 27F outside right now. Any thoughts. Car is 95 E320 176k mi.
thanks

My former 95 E320 did the same when I replaced the pump and hoses, sealing all leaks. Car ran hotter thereafter -- which is normal.

Leaky coolant system runs cooler -- seems counter intuitive but that has been my experience.

Is the fan clutch locked up at this temperature? It should be howling, my car is a diesel but it was doing something similar, my clutch was dead - refilled it, now working - then also cleaned out the condenser fins which were packed with dirt and bugs.

After that the temperature came back to normal

Have you fully bleed the system? You might have air locks!

kranje, two potential causes come to mind for the elevated engine operating temperature: stuck thermostat and less-than-full cooling system. What brand and temperature thermostat did you install? Recommend a Wahler. As mentioned it's possible the cooling system is not completely full. I normally fill the engine block via the thermostat housing before installing the thermostat. Before installing the upper radiator hose I attach a short piece of clear hose (same size as radiator hose) to the upper radiator connection and use it as a funnel to fill the radiator with coolant mix ... leave the cap off the expansion tank while filling the radiator. Once the radiator is full install the upper radiator hose, reinstall the cap on the expansion tank and run the engine with the heater on until the engine reaches operating temperature. It may be necessary to add coolant to the expansion tank so it's at the proper level when the engine is cold.

It might be time for a new radiator as well. My friend Hit Man X recommends changing them out after 10 years or so. I've done all but one car and they all sit at 80C during most situations. The m103 will inch up above towards 85-90C but only with AC on and at idle/traffic.

As you said you have only installed new wp and thermostat due to leaking wp, so you never had a over heating issue prior to this. The only possible cause that's coming to mind is an air lock In the system, my suggestion to you would
Be to run the engine with heater on and rev the engine at about 3000 rpm or so for a few minutes giving the engine a break every now and then in-between, with the expansion tank cap off. This should Get rid of any air locks you have (hopefully), if This didn't help check for correct operation of the circulation pump, just feel it with your hands and make sure the motor is running. If this was also working and you were getting the heating issue then feel around the radiator all around an make sure you don't have any hot spots, if the temp is the same all around then there is nothing wrong with. All these tests should bring you to a conclusion, good luck :)

I alway drill one tiny hole in thermostats to let air burp.

Thanks for all the replys.The WP was a Graf and thermostat was Behr 87C.I think I got all the air out from the system and now it runs around 90C-95C outside temp. is 30F.The car ran just a bit past the 80C mark before.I'll put back the old thermostat see what happens its 10min job.

thanks in advance

I used a 76c thermostat,to keep her a tad under 80c

Check to make sure you have the thermostat installed the right way. Undoubtably you do, but well you know!

I put back the old thermostat it read 87C.Behr I think it's stil the original one I've owened the car for 12yrs. tempeture is back were it was running before just a bit past 80C mark it always stayed there from day one. I don't get this the new one read the same thing it ran 90C-95C what will run at in summer with a/c on 110C.
I forgot the user name here on this forum. He always writes (if it works don't replace it).
Thanks for all the replys

I need to replace my radiator. I have replaced waterpump, fan clutch, and tried all of the thermostats, including the one from MB and engine still runs hotter than it did prior. Have all of the air out of it. What is left, is an original 20 year old radiator that may not be flowing as well as I'd hope. Who knows what crud is plugging it up inside from additives and head gasket sealant?

I think I paid just under $200 for my w201's radiator. Same for the 420SEL.

I think you are going to spend a lot of time chasing something that is normal. you cant compare an old tired thermostat to a new one. There are numerous threads about this very issue and they all come to the same conclusion. A new 80c thermostat is going to have the car anywhere from 85-100c for a normal day.