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Old 01-09-2019, 05:54 PM
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scout4bta scout4bta is offline
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Join Date: Apr 26, 2018
Location: SE Arizona
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New thermostat broke Tstat housing

Bought a new Tstat same brand as the old one. Cleaned every thing up, installed the new Tstat and preceded to tighten down the bolts. As I was alternately tightening down the bolts heard a "snap". Found a crack above the bolt flange on the drivers side.
On the new Tstat the formed edge on the outside was .068" high, the old one was .048". The depth of the counter bore in the manifold for the Tstat is about .035" deep. Seems an additional .020" is too much for the gasket to compensate for.

The Tstat brand is Fail-Safe manufactured by MotoRad, Hecho En Mexico.

Anyone else have this problem?
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Old 01-09-2019, 06:33 PM
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Tripwire Tripwire is offline
hey,does anyone here know how to.......
 
Join Date: Jul 30, 2000
Location: WA State
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its happened to me on baby jeep 2X.. on a OEM one and on a aftermarket.....luckly the local parts store had them in stock...NAPPA should be able to get you one, or i can send you one i have off a old rig..

Me thinks it was a thermal stress failure or a speck of grit between the mating surfaces

PM me

steve
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Old 01-09-2019, 08:33 PM
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scout4bta scout4bta is offline
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Join Date: Apr 26, 2018
Location: SE Arizona
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Quote:
Originally Posted by Tripwire
its happened to me on baby jeep 2X.. on a OEM one and on a aftermarket.....luckly the local parts store had them in stock...NAPPA should be able to get you one, or i can send you one i have off a old rig..

Me thinks it was a thermal stress failure or a speck of grit between the mating surfaces

PM me

steve
The Tstat housing is "pot" metal, very brittle. There was no grit on the gasket, the only stress was the extra .020" height of the new Tstat flange that was formed wrong.
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Old 01-10-2019, 12:39 PM
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tgreese tgreese is offline
 
Join Date: May 29, 2003
Location: Medford MA USA
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When I worked parts counter (30 years ago!), broken thermostat housings were very common. The usual cause is misaligning the thermostat with the recess in the housing or manifold. This traps the edge of the stat on one edge and the housing breaks on that side. Not saying this was what you did, but it was a very common problem. The housing must set down tight on the gasket all the way around before you start tightening the bolts. If the stat flange is too thick, you could use an extra gasket.
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Last edited by tgreese : 01-10-2019 at 12:50 PM.
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Old 01-10-2019, 01:02 PM
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scout4bta scout4bta is offline
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Join Date: Apr 26, 2018
Location: SE Arizona
Posts: 41
tgreese,
I was thinking of using 2 gaskets, but figured that it would give it a source for more leakage. So Im going get my money back on the new Tstat and reuse the old one.
I tested the old one and it does work, heated it in a pan of water and it does indeed start opening at 195℉, I thought I was doing my self a favor by getting a new one not knowing the history on the wagon/engine.

As far as the misalignment that was my first thought but after removing the Tstat housing the Tstat was fully seated in the counterbore.

If the old Tstat does ever fail I'll know what to look out for.
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1980 IH Scout/4BTA/NV4500/Atlas 4.3/DYNO:172(HP),432(ft-lbs)25mpg
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Old 01-10-2019, 03:04 PM
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acct21 acct21 is offline
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Join Date: May 20, 2014
Location: Austin, TX
Posts: 721
I changed my T-stat a few years back, and have been ignoring a weeping leak at the T-stat flange for several months.

I pulled everything off, prepped the top of the intake with a Dremel and a wire wheel (same to the bottom of the T-stat housing). Then I put a thin layer of the Permatex water pump sealant on the intake, a thin smear on both sides of the Fel-Pro gasket, and a thin layer on the T-stat housing. Carefully put it all together, and hand-tightened the bolts until the Permatex just started to squish out. Waited 48 hours, pulled the bolts, put thread sealer on them, and tightened to spec.

That little extra smear of Permatex in there should hopefully have 'levelled' out the gasket and prevented any stress on the T-stat flange. So far it's been a couple of months, and absolutely no leak whatsoever.
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