Funky thermostat?

[dlundblad]

On top of my half shaft starting to go out, my newly installed Mopar 195*F thermostat is acting weird.

According to my temp gauge, the coolant goes up to just below 210*F then quickly drops to about 182*F before slowly rising back up to 196*F. For the most part, it'll stay at 196*F, but yesterday, I noticed it randomly drop down to 182*F again. It took a few minutes, but it went back up again to 196*F. I do not have a scanner that tells me the coolant temp so I just did the math by looking at the gauge, which I realize isn't entirely accurate.

Could it be that I just didn't let the air out of the system? I tried burping it a while back, but the antifreeze eventually starting overflowing from the fill cap in the radiator well before the engine was started to warm up.

Thanks guys.

 

[HTSS_TR]

Your thermostat is working okay, nothing wrong with going up to 210F then settle down to 195F few minutes later.

 

[edwardh1]

some foreign cars I owned has a 1/8 inch hole in the stat "plate" to allow smooth warm up, i.e. some flow always. The us company replacement did not have the hole so I drilled one

 

[SteveSRT8]

Originally Posted By: edwardh1
some foreign cars I owned has a 1/8 inch hole in the stat "plate" to allow smooth warm up, i.e. some flow always. The us company replacement did not have the hole so I drilled one


it's a great idea, but the hole is for steam or air not flow...

 

[rslifkin]

I've noticed the 4.0s sometimes do that. It's possible it's a faulty thermostat, but it also could just be an artifact of those engines not having a ton of bypass flow (only coolant bypass with the t-stat closed is through the heater loop, IIRC). That can make things not warm up 100% evenly and may cause less than smooth t-stat operation until it's good and warm.

 

[simple_gifts]

aka the jiggler valve.

 

[Toaster_Jer]

I really wondered about that myself,because I have an 88' Pontiac 2.0 with that same problem. I have replaced a number of thermostats in it over the years(10+). The only possible answer I have been told is the thermostats made for that engine are all defective and I have dealt with it for over 25 yrs.

 

[Oldmoparguy1]

Originally Posted By: dlundblad
On top of my half shaft starting to go out, my newly installed Mopar 195*F thermostat is acting weird.

According to my temp gauge, the coolant goes up to just below 210*F then quickly drops to about 182*F before slowly rising back up to 196*F. For the most part, it'll stay at 196*F, but yesterday, I noticed it randomly drop down to 182*F again. It took a few minutes, but it went back up again to 196*F. I do not have a scanner that tells me the coolant temp so I just did the math by looking at the gauge, which I realize isn't entirely accurate.

Could it be that I just didn't let the air out of the system? I tried burping it a while back, but the antifreeze eventually starting overflowing from the fill cap in the radiator well before the engine was started to warm up.

Thanks guys.


Is this a genuine mopar parts thermostat? If not, get one. I have had dismal results with after market thermostats. The mopar ones have a little ball check valve for venting air. It really matters.

 

[eljefino]

This could be a mopar thing. Hear me out. Ignore me if it just started though.

I had a 94 dodge spirit. Got it cheap, fixed the head gasket, kept an eagle eye on the temp gauge. I even put a burp hole in the thermostat flange.

When I hammered it uphill in winter time, the thermostat opened *more* to let the heat out. More ice cold antifreeze came back from the radiator and hit the gauge sender, which is on the other side of the head from the thermostat. So the more work I made the engine do, the lower the gauge read.

If I let it idle in traffic, the gauge smoothed out and crept up until the fan came on, then it promptly dipped.

This could be you, too. I recommend the burp hole, I believe it helps water currents near the thermostat pellet which keeps the pellet "more involved". You burped the air the first time the 'stat opened.

 

[dlundblad]

Looks like it is just normal then. I just don't remember the old one doing this.