I have a 93 MAX 4 cylinder
A few weeks back I noticed that the temp gauge was only getting up to 1/4 to 1/3 of the way up. Before then, the gauge would always stay right in the middle after warming up.
I figured it was the thermostat so I decided to replace it.
The thermostat that was in the truck was rated at 190F.
The closest thermostat I could find was 195F so I bought that and installed it. It was a Stant basic thermostat.
Now, only when the engine is totally cold and I start the truck, the temp climbs very close to the upper limit, about 3/4 of the way up the gauge, then the temp goes back down to the middle of the gauge and it stays there.
However, if I drive somewhere and let it cool off some, but not totally cold and re-start the truck, it doesn't spike the gauge, just goes to about halfway and stays there.
I went ahead and got a different thermostat (Stant Superstat, supposed to somehow be better than the basic thermostat I guess) and it's doing the same thing.
I'm sure I installed it in the proper orientation with the jiggle pin at 12:00 and the spring side towards the engine.
I've considered that maybe there is air in the system, but did not see any sort of bleeder on the thermostat housing.
I just filled the radiator and reservoir and started the truck but never saw any bubbles coming out of the radiator fill neck.
Sadly, I cannot find my shop manual for assistance.
So I'm wondering:
1. Could it just be air in the system messing things up?
2. Could it be an issue with the temp sending unit or gauge?
3. Would a 180F thermostat solve the issue?