I replaced my own thermostat this weekend, however the part I purchased only came with a small thin rubber gasket that fit around the thermostat, and the entire unit dropped into the thermostat housing. Put a little goop in for safe measure, and bolted it down.

Well, a few miles later, the gasket blew out - together with the entire contents of my radiator. Did fine driving down the freeway with no water (Stayed at the "L" of Normal), but once I pulled off the freeway, got the "overheat" light.

So....what am I missing here? Is there a gasket my friendly parts store failed to provide me, or is there an art to the thermostat?

Thanks.

 

I dont' know if they are different on trucks older than '99, but I just flushed my coolant so had my thermostat apart, and it's just a rubber 'o-ring' gasket, sits on top of the thermostat, a couple bucks for a new one from O'Rielly's. You might of not had it in there correctly, that would be my guess anyway. I was worried about it popping out when I put it back together, but it hasn't been leaking. That's all there is to it anyway, just the one gasket. I'd go buy another new one and try again. My .02 cents.

 

Sounds like it was the wrong gasket. It should be a square-cut O-ring that sits on top of the thermostat, not around it. The recess in the waterpump should keep it in place. Check to see if the bottom of the water neck is flat. You may need to straighten it, if it is warped. Put a little bead of RTV (silicone) on the water neck and bolt it down. Give the RTV a little time to "set up" before driving. This is how I did mine, with no leaks.

 

Also be sure you have the right thermostat. Did you compare the new one to the old one? From what I understand the auto parts will sell you the wrong part. The one you need is longer than a typical thermostat. If you have a shorter one the coolant flow will be wrong and cause incorrect cooling flow.

Jeff

 

Jeff brought up a good point. The thermostat should have the stem on the bottom that closes a bypass hole when the thermostat opens to allow full flow to the radiator.

 

Also part of the problem is the use of too much "goop". O-rings do a fabulous job of sealing things up all on thier own. All you want to do is to slightly wet the contact surfaces with no extra blobs anywhere. See, the extra goop will get trapped in the groove and when you tighten it down it creates extreme hydraulic pressure in the o-ring channel because liquid is not compressable. It will simply shred the rubber of the o-ring and then you effectively have no gasket.

 

Thanks for all the great posts. The truck had NO thermostat to begin with (it used to be run in Calexico, California. Average temp is 80 degrees, so I guess they didn't need it. Also likely why they by-passed the A/C clutch and left it in the "on" position 24/7)

The only gasket I got, was an o-ring, that went around the thermostat. It fit perfectly into the water neck, and I had placed only a thin coat of goop.

Anyway, I drove straight to my trusted mechanic, who will be doing it the right way, including a new Thermostat, for $60.00

My in-laws have a saving, "Cheap usually ends up being expensive". I should have let the mechanic change the thermostat.

 

Hahahaha. (Good natured laugh here)
I am a mechanic by trade and have fixed few "repairs" too. Thanks for the chuckle. And I don't charge a ripoff price either.