I have a 91 240 that i have recently replaced the water pump and thermostat, i dont have any leaks and there is no water in my oil. For the past 2 days the temp gauge has read on the cooler side ( a little under the middle mark) as it should and then today out of nowhere it jumps to almost the 3/4 mark, it was slowly coming down as i got home but is this normal? I was hoping my car would remain cool with a new pump and thermostat, what else could it be? Im pretty sure my head gaskets fine because when i turn on the heater , it gets cooler and the gauge goes down. any ideas? IT was a hot day but come on , can i keep the car cool?

matt

 

radiator man....same crap happened to me and burnt my tranny oil.....I replaced the thermostat and pump and the temp sensor. Still hot and erratic so the culprit is the radiator. check your trans fluid(if automatic) might be brown already.

 

new you could get one for 120 or used for 35 junkyard though....? Maybe with shipping one of the sponsors can give you a deal. IPDUSA OR FCPGROTON

 

What was the ambient temp when it went to 3/4's? What sort of driving...stop and go or freeway? Were you running the a/c? How about as it was gradually cooling back down...freeway or stop and go? I agree with redbottle to a point it does sounds like the radiator BUT...generally clogged rads don't allow the car to cool down unless...it got hot in stop and go traffic w/ a/c on and then you got out in freeway traffic and the extra wind helped cool it down.
If you decide to swap the rad out be sure to get the 3 row version. Also, keep in mind an air lock in the cooling system could do what you describe...although I'm guessing it was already having cooling issues before and that's why you swapped the t-stat and wp. A neat trick to allow more air to the radiator is to loosen the mounting hardware of the a/c condenser. Wedge a 1" thick piece of wood at the bottom on either side and tighten it back down. This allows more airflow to the radiator. The only other thing it could be is your fan clutch. If you replace it, give serious thought to buying one of the Asin tropical HD fan clutches from davebarton.com They provide a lot more airflow at slower speeds than the stock one.

 

that's right the fan clutch...
3 row version? what are the stock?

 

2 row. Actually, the 2 row aluminum and plastic ones by Blackstone or Nissens are pretty good too but I've had really good luck w/ the 3 row all metal.

 

OK EVERYONE STOP!!! Here's the proper way to proceed...go get yourself a IR laser temp gun or borrow one...then when your car get "hot" take the temp of the radiator and the thermostat...point the laser at the bolt right on top of the thermostat housing...should read 180-190 the taken temp of radiator..if the temp of radiator is same on both sides..you have a bad radaitor if it differs by 20-30 degrees you just svaed yourself $150...and time... TEST TEST TEST TEST TEST TEST...EVERYBODY NOW...TEST TEST May just be a bad temp circuit board...who knows?? Or your using your A/C and your aux fan is not kicking on...could be nothing...TEST

 

Only other thing fan clutch??...sorry but I strongly disagree. Ummm bad temp circuit board? Aux fan not kicking on if he's using A/C? Assuming he's not low on fluid...fan clutch is only bad if car overheats at idle...if car is overheating while driving(truly overheating not false readings cause of a bad temp circuit board...) then usually thermostat,aux fan not kicking in if using a/c,radiator,low fluid...but sounds like he has a bad temp circuit board if it's already registering low...should not register low should be right in middle if everything is clicking along just right...