My '90 Bronco with 5.8 was running on the cool side so i bought a replacement 195F thermostat and replaced it.

The old one had no O Ring and the new one bought at Autozone didn't come with an O ring but i would think there would be one.

Anyway replaced it and still running just as cool. I am guessing an O ring was needed.

TIA for answers

Matt

 

shouldn't be an o ring anywhere. the T-stat housing should have a resesed area for the tstat to sit in, a gasket or bead of silicon round that and bolt it down evenly making sure the stat doesn't move out of that groove.

now if you are simply going by the stock gauge its not accurate at all. get a mechanical aftermarket gauge to see what the temp accurately is.

 

Thanks.

The top hose out of the radiator and the T-stat housing show about 160F with my IR temp gun.

The truck runs cool which is why i did a compression test today. I was worried there was a cold cylinder situation but i doubt that as the compression number as decent for a 25 year old truck.

All cylinders were 148 - 150psi but cyl # 4 which was 126 psi.

I cut cardboard and covered about 80% of the radiator to get it to rise into normal. I then checked with the IR temp gun and got the above 160F off the T-stat housing and top hose which was lower (150F)

If i'm at 160 at the housing why is the T-stat opening?

 

perhaps your fan clutch is not working correctly. basicly stuck and operating all the time which may cause it to run cool. is it easy to turn the fan by hand? it should spin freely for the most part and tighten up when it gets hot.

 

I checked it, the fan spins or can be turned by hand with the same moderate resistance as the new fan clutch i looked at at the parts store today.

My fan spins in the very cold, is it supposed to? The new fan clutch i held today would do the same as there is moderate resistance. In other words the fan would not be still on any start up if this new clutch was installed. It felt just like mine.

I assumed they always spin even in very cold but spin faster once a certain temp is reached correct? But this seems wrong to me.

Does yours sit still on cold start ups? Mine does not, it always turns the fan even on 10F mornings like this morning. It is not seized though, i can turn the fan with my hands as i said. It feels as good as the new one i held with no slop or binding.

Thanks in advance for the help.

Matt

 

yea it will still turn when its cold.