Howdy. Ever since I replaced my radiator, the car runs super cold on the highway/mountain driving. First thing that comes to my mind is the thermostat maybe rated for temperature that are a lot higher? The only thing that makes me think otherwise is that even on the highway the car runs cold. Any suggestions?

The car in questions is a 740, NA, 1990, Automatic. Thanks!

 

A respectfully dumb question, but are you sure the thermostat was in place when you did the swap, assuming you changed the hoses as well?

That's where I would start questioning.

 

I'm pretty sure the thermostat was in place prior to the swap. I replaced the radiator and the upper hose. I've never touched the thermostat and I don't even know where the sucker is. I was assuming it was either integrated in the radiator or somewhere on the block...

 

How cold is it outside when you run? Sometimes on cold days, driving at high speeds just cools it down real fast.

 

The thermostat is at the block where the upper radiator hose connects. Just remove the two nuts that hold the domed shaped piece that the hose connects to. Pop it off and you will find the thermostat.

My be is that it is stuck open. Replace it with a decent brand - Wahler comes to mind. If you are in cold climates (like the upper midwest), use a 92 degree C temperature rating. If you are down south, an 89 degree C rating would be more appropriate.

 

Where does the neddle in the temp gage when the car is warm? Is it in the middle? Also when the car is running feel the upper rad. hose to see if it is hot.

 

I'm in the NW. When the car does warm up (sitting in traffic or going up a hill), the needle will move CLOSE to the middle but never really gets further than 2/3 of the way to the middle.

I will pop the housing off and see if that sucker is in the open position. In which case I imagine I have to replace the tstat? Is nobody recommending cleaning it and trying it as is?

Thanks guys!

 

Those are too cheap to not replace it. Cleaning it is a bad idea and more than likely won't do anything to it.

 

How long does it take for the needle to get to 2/3? Also, do you get heat then?

With a properly working thermostat, the engine should get to operating temperature within 5 min of normal driving. If it takes a lot longer than that or only does it in stop & go traffic, most likely it is your thermostat.

Like icthus says, thermostats are cheap - usually less than $15. If your going to pop the dome off, no reason not to replace it.