After replacing the old thermostat with a new one the SDL is now overheating, even at idle!

The new one was slightly smaller than the stock one, so I figured I wouldn't need to do a modification, but instead it overheats worse than the original. I'm thinking maybe the foreign auto parts place possibly gave me the wrong make and model thermostat. My mech. said he's almost 100% sure he put the thermostat in correctly, but now he has to go back and double check, p.i.t.a. .

Any ideas or opinions are greatly appreciated!!!
Thank you!

P.s. I'm probably going to have to put the old thermostat back in worse comes to worse. Is this a bad idea? I was thinking about moding it before it's put back though...

There's nothing wrong with the new thermostat.

Remove the upper hose at the connection to the radiator and completely fill it with coolant. Reconnect it quickly without losing any coolant.

Problem solved.

Your fan clutch may be shot.

Your temperature sensor that triggers the electric fan may also be shot.

Don't ask me how I know this.

Dan

__________________
Dan

86 300 SDL
New odometer gears, new rubber fuel lines, removed and plated EGR, redone underhood vacuum system, BoostValve on the turbo, IPod only sound system, changed a couple of window motors, refinished the console wood, changed a couple of switches, removed welded and replaced my oilpan after I cracked it (driving like an idiot), new glowplugs, new/used glowplug relay, sunroof repaired, antique brass boost gauge on the hood.

There are also different styles of thermostats. Most of the Behr ones have a little "rivet vent" on them which has to be installed pointing up on a vertical housing to work right. These will vent out trapped air much better than the ones which don't have the vent. If yours has the little vent be sure it is pointing up and if it doesn't I would exchange it for one that does. Also, you should know that the temperature ratings of these has been raised over the years. I still use 79C models but have been given 87C ones even from the dealer and told they do not make the 79C any more. This is not true, you can buy 79C Behr thermostats...those are the ones I recommend using.

__________________
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

I ended up having to put the old one back in, after moding it just a little bit! Now it runs better than it did before!


Is there any thing I should be worried about as far as putting back in the old thermostat? I used the new seal, but I'm thinking about the new thermostat back in exchange for either cash or the correct one.

Thanks for ALL replys and posts!