Bad Thermostat?

[Drey]

My 91 K5 had a thermostat that was sticking and it was gettin way to hot. About a month ago I put a new one and its been working great up till about a week and a half ago. Its a 195 thermostat. But my K5 gets up to about 210 before it opens up, once it drops it goes to that 170 range and then doesnt climb again hardly at all.

Im taking it on a roadtrip end of january and really want to have this worked out.

 

[4X4HIGH]

On my 89 blazer with a 195 t-stat the factory temp gauge shows right about the 200-210 range and always stays right there. Have you verfied the temps with an IR gun? Maybe your gauge is faulty?

 

[Drey]

Whats do you point your gun at to verify the temp? I would guess a hose would give the most accurate rating.

 

[toomany]

I'd say thats fairly normal. My K5 runs around 200-210 going down the road with a 195* t-stat in it. What makes you think that it isn't working? Is the sending unit in the head or the intake? Point the IR gun at the hoses, thermostat housing, coolant in the radiator, that should give you a good idea on what the actual temp is.

 

[Drey]

just that it has to get to 210-215 before it opens up, and after that it never gets above 170. Im wondering if something is bound up and it is hard to get open then it gets stuck open.

 

[broke73]

Sounds like a bad t-stat to me. If you bought it from auto zone I would almost gaurantee it. I had to replace mine from there 3 times then finally went to carquest and threw the one from auto zone in the trash. No problems after that.

 

[Drey]

OReillys, Ive usually had good luck with stuff from there.

 

[4X4HIGH]

Whats do you point your gun at to verify the temp? I would guess a hose would give the most accurate rating.

Well since you want to compare your temp gauge with what the engine is actually doing you want to point the IR gun at the temp sender.

 

[dyeager535]

It's gotta be the thermostat, IF the gauge is proven to be correct. If the engine can be kept cool, which yours can based on the temperatures given (and probably bears out that the gauge works) I'd suggest going and getting a Delco thermostat.

Have yet to hear of a problem free aftermarket brand. Even the expensive hi flow ones have gone downhill from what they used to be.

 

[bp71k5]

To me it sounds kinda normal too unless it stayed at that high temp for a long time.

The thermostat probably opens at 195 and with some innaccuracy between the temp sender and the thermostat it just takes a bit of time for the extra water flow to start reading at the gauge.

I guess it depends how long it takes but mine drops from 200-205 pretty quick.

 

[dyeager535]

Thermostat on mine seems to swing pretty quick on the gauge, but it's a very small amount between open/closed. 40* temp swing doesn't sound good to me.

 

[willyrocket]

Wow, I have just recently started the same problem. Only mine goes up to about 240 max, and the longest it sits there is no more than a minute, then it drops quickly to about 200-210 with no further discreps. Its a 195 from autozone also. Could there still be some air in there for it to cause this problem? Or just the fact its an autozone part.

 

[dyeager535]

If the temp spikes like that, there is only one thing that can cause it, the thermostat. When coolant goes through the block too slow, it gets hot, and the only thing that is a restriction to flow is the thermostat. Being sticky is a common aftermarket thermostat problem.

 

[willyrocket]

Kind of what I thought also. T stat thats in it now, was a replacement due to the previous one having same issues. Looks like I need to shop somewhere else for parts..........

 

[dyeager535]

I hate to say it, but Delco is about the ONLY thermostat I'd trust anymore. Used to be that Robertshaw made a good one, but it too got bad after time.