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Leaking Thermostat Housing ?

Hylander

NAXJA Forum User
Location
Texas
I can't seem to get my TH to stop leaking.
It is leaking through the gasket.
I have replaced it twice, once just last night and today it is still seeping.
I tried Gasket with no RTV, then Gasket with RTV.
Leaks at the same spot each time.
I'm thinking the Housing is warped ?
 
I can't seem to get my TH to stop leaking.
It is leaking through the gasket.
I have replaced it twice, once just last night and today it is still seeping.
I tried Gasket with no RTV, then Gasket with RTV.
Leaks at the same spot each time.
I'm thinking the Housing is warped ?

Which spot, specifically, is it leaking from?

If it's coming from somewhere near the base, inspect the mating surface on the cylinder head (pay particular attention to the screw holes) and on the housing. If no defect is visible, get a flat bastard or mill file (or 120-grit sanding sheet stuck to a rigid flat surface) and clean up just enough to get it flat. I'd probably put a coat of machinist's blue dye on the thing before I started cleaning it up - it will show up any unevenness in the surface (as soon as you start sanding/filing) and tell you when to stop. You should only remove enough material to make the surface flat (it is unlikely that you have to do any cleanup work on the head casting.)

Again, pay attention to the screw holes in the housing - check for any cracks between them and the "main chamber" that could be passing water when hot or under pressure.

Make sure you haven't "corroded through" anywhere on the two hose nipples, which could give you a leak from under a hose. Also, you can get a "corrosion channel" on the outside surface that can do much the same thing. In either case, the repair is actually replacement.

Tell us the specific location of the leak on the housing, and you'll get more specific advice.
 
just use RTV. I applied 1/4" RTV bead, finger tighten the bolts, but leave some room between the surfaces. I waited 24 hours, then went back and tightened them down, and no more leak.
 
It is leaking just about 1/4" above the Lower Bolt and
extending up about 1.5" right through the gasket.
I'm thinking I should just order a new Housing, But will try the Flat File
to clean it up.
 
It is leaking just about 1/4" above the Lower Bolt and
extending up about 1.5" right through the gasket.
I'm thinking I should just order a new Housing, But will try the Flat File
to clean it up.

Wrap some sandpaper around a piece of 2x4 and hit the gasket surface--that will show you if you have high/low spots.

Getting the mating surfaces clean is a must--bare metal. Check around the bolt holes in the head with your finger and feel if the surface is raised. Use a regular scraper to clean the head of any left-over gasket/sealant.

I'm old school. I use Permatex non-hardening on the t/stat housing, with a couple dabs to anchor the t/stat in the housing, and I never put anything on the head mating surface. You don't want sealant on the head itself where it is so hard to clean up.
 
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I had the same problem a while back. For me the problem was a small amount of coolant in the head. With the housing off no coolant would drip out but with the housing in place a tiny bit would seep and ruin the gasket/rtv enough that it would then later leak really bad.

I took a fluid pump and got as much of the coolant from the head as possible, solved my problem.
 
I had the same problem a while back. For me the problem was a small amount of coolant in the head. With the housing off no coolant would drip out but with the housing in place a tiny bit would seep and ruin the gasket/rtv enough that it would then later leak really bad.

I took a fluid pump and got as much of the coolant from the head as possible, solved my problem.


I noticed this when changing my tstat - I sucked some out and jacked the front of the engine up to make the coolant sit back. Problem solved! Need a dry surface.
 
I cracked the Hesco unit I bought for my XJ earlier this summer, and with a little grinding and JB weld (ghetto I know) it works great now. DO NOT torque the tstat housing down very hard!!!
 
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