Thermostat / Temp Gauge / Cooling Question

[miketegra]

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?

Thoughts? Advice?

Thanks!

Mike

[LSR Mike]

Sounds like the thermostat is slow to react and not opening fast enough from a cold start.

[pennyman1]

the jiggler in the stat is there to bleed the air out, it does sound that the stat is the issue here. For some reason, stant stats act weird in these trucks most of the time.

[vaprobe87]

Mine has a Stant 195 and does the same thing. I always keep a eye on it to make sure it don't get too hot but have never had a issue.

[miketegra]

Thanks for the replies.
I think I'm going to just get one from the dealership. (P/N MD972903 if anyone is interested). It's rated at 88C.
I'll post results after I put the new one in.
I do have another question about bleeding air from the cooling system.
I've noticed there does not appear to be a bleeder valve.
After I changed the thermostat, I just filled the radiator, tried to burp the upper radiator hose, and let it run with the radiator cap off. I never really saw any bubbles come out. I swear it feels like there is a bubble stuck at the top of the upper radiator hose. I know, sounds kinda crazy. It sorta gurgles when I squeeze it.
The upper hose is aftermarket and has a small hump in it. Don't know if this is normal? It looks like the top of the hump is above the top of the filler neck. Wondering if this is causing a bubble. I would think it would quickly work itself out. upperhose.jpg
Radiator and reservoir have stayed at the full level since I first filled it after changing the thermostat.
Any tips on bleeding the system?

[itsnotthesizeofthedodge]

Screenshot_2013-11-10-18-25-05.jpgGo to harbor freight and buy a coolant funnel replace the tstat fill it up with the funnel on the radiator untill it stops going down leave the funnel half full crank it up let it run when the tstat opens up it will drink some of the coolant let it run untill the water is warm in the funnel system is bled

[miketegra]

Thanks! I will pick up one of those filler kits.
Do you think the shape of the upper rad hose could be an issue?

[camoit]

It should not be an issue. Just be sure to turn on the heater when filling it. When you rev it up a bit when cold it should suck down the water. Then top it off. Just stand there tell the T stat opens. The water will start to rise up into the filler neck. At that point pop on the cap and make sure your bottle is full. That should do it. Just remember thermostats are built on a production like whizzing along at 300 per minute so the 8 year old Chinese kid with the missing finger operating it dosn't check opening tempters for quality that often.