No I don't mean it's "cool" when it's running. I tried to find the thread about our 400 running cool, taking forever to get to running temp. I have owned my 93 400 since last September and have been fixing issues as they arise. I thought maybe my old thermostat was probably stuck open. I replaced it with a new quality thermostat 180F (about the easiest thing to do on a 400) and now she gets up to running temp quickly. As most of you know running your car cool can cause problems in the long run so if you notice this problem I suggest you replace the thermostat ASAP. Also a great time to replace your coolant.

 

was the old one all caked up or broken? glad you got it figured out thanks for the info on the fix for those who have the same problem.

 

No it wasn't caked up or broken. I think it was so fatigued that it opened up as soon as any warm coolant hit it. When I pulled it out it was closed. I think I'll put it in some water on the stove and see how long before it opens.

 

I had a thermostat with piece of rubber keeping it open....... Same issues. Good info

 

Hmm.. I just replaced my thermostat with a brand new oem unit and mishimoto radiator. Now the car takes forever to warm up.

 

Another part to go into the "SC Doctrine" as a popular break.