hello guys i have a 1990 240DL, just change the water pump flush the radiator and the car still runs hot, any suggestions. thanks

 

Does your temp gauge loom up around the top of the gauge, right under the red zone? Mine does that, especially on hot days. When it gets up right to the red, the fan kicks on and brings it back down. I'm gonna put a 180 degree thermostat in it soon here and see if that keeps it down in the comfort zone.

 

realize, the 240s (and 740s and 940s) have an equalizer circuit on the temp gauge on the dash.... if its anywhere in the 'normal operating range', the needle should be pretty much dead center. it only goes above this when its really really hot.

I'd wonder if you have a sticking thermostat that finally pops and lets the water into the radiator when its really hot. you need a new thermostat, doesn't have to be a 180 one.

also, the first poster, the thermoswitch on your fan might be out.... or, I believe those are supposed to be two speeds, and only go into high when they are really hot, so maybe your medium speed isn't working at all.

 

Same thing happened to me, changed fluid, ran hot. I finally just said the heck with it, and DROVE it around right under red, and it just finally cooled down to normal operating temperature. Like said before, sticky thermostat is the likely culprit, especially if the system had air from a flush and little fluid was in contact with the thermostat.

 

I went through the same thing too. Changed the water pump, rad fluid, hoses, thermo, thermo housing and my 1988 240 wagon still ran hot. Took my radiator to get it professionally cleaned-still ran hot. Finally I decided to replace the radiator and my car been running great. I live in Phoenix,AZ so it's been +105F every day(40 mile daily commute). I run my AC too and the needle stay right at 9 o'clock. Your radiator could be clogged-->"damaged cooling fins on your radiator core". Good Luck

 

I am tempted to think that this is NOT my issue, as I mentioned before, right when it starts to creep up to the red, the fan must kick on, because it cools down so qwikly I can actually watch the needle drop back down, all the way to 9 o clock, until it gets hot again and this cycle repeats itself. Pierce, you mentioned that when I replace the thermostat, that it doesnt have to be a 180 degree. I was wondering, why not? I'd prefer the fan to kick on earlier before it gets way up there...but then again, there might be a reason it runs at a higher temp than newer cars, that I'm simply unaware of.

Rock Auto ( a GREAT place to buy car parts online, I might add) shows thermostats ranging in temps from 195 down to 180...The ones that say "OE Temperature" are 195. So Pierce, you've had all the answers so far, how bout this???

Thanks buddy!!

 

ok, there's two separate things here. the thermoSTAT is a purely mechanical thing on the output of the water pump that controls whether the water circulates inside the block, or gets routed through the radiator. there is also a thermoSWITCH, which *is* another sort of thermostat, which controls the electric fans.

I am thinking the thermostat could be causing these symptoms, its staying closed until the engine is really hot then snapping open and letting the water go through the radiator.

 

You're the man Pierce. Thanks as always!

 

btw, you normally always replace the thermostat when you replace the water pump, just as a matter of practice. my mechanic replaces both of them when he does a head gasket whether they need it or not (the labor for the headgasket job is already high enough that the extra work and parts to do the pump-n-thermostat is trivial).

 

There was a thread in July '11 about replacing the thermostat in the 240 series -- which is what I'm aiming to do in my '92 240 DL. HOWEVER, the good guys at my local NAPA (and the distributor they called) said there's two temps for my make and couldn't make out which one I should get -- a 180 and a 195. I saw Pierce wrote, in one post, that the thermostat someone was gonna replace need not be a 180. But can it be a 180? Or should it be a 195? Can I use either one?

Thanks
Elsa

 

a lot of people like to put the lower temp thermostat in to 'keep the engine cooler'. but, engines run optimally when they are at the full operating temperature, so I'm not 100% sure of that justification is valid. I'm pretty sure the 195F one is the standard one.

 

I would use the 195° one like Pierce recommended or look at your owners manual (there is one online). The thing that most people don't understand is, the temp needle is programmed to sit at 9 o'clock from the time the motor temp gets to about 175° and stay there until it gets as high as 220°. So the 195° stat will be wide open far before the car gets real hot. Coolant under pressure does not boil until 275°, so you have a long way to go.

The car will preform better and last longer at the proper designed temp.

 

Thanks Pierce and RSPI,

I was leaning towards the 195 and I'm glad to hear yall think its the better choice. My manual says the "opening temp" is 190. So 195 is closer I guess. Good to know the coolant boiling temp, too! Thanks