thermostat gasket leaking

[mad dog]

I ended up filling the pits with an industrial epoxy product and then sanded the intake smooth as can be, i then installed the O- ring housing that Cruze recommended.
Im going with the flowkooler WP and the Robert Shaw thermostat....trying to cover all the bases...

 

[jeff alder]

I didn't see where any clearances were an issue to warrant chucking a manifold on a Bridgeport table. I used a palm sander. Flat is flat no matter what you use to get it there.

 

[ddart cart]

Mine leaks a tiny bit with a new china gap, new housing, and blue felpro. No sealant. Doesn’t bother me much, I have things higher on the to do list like the heater core that started to leak a little, but I’ll get to it. I’ll try a little sealant on both sides and see if that does it.

 

[Dana67Dart]

I had the part number for Real Gasket once upon a time. Try Ebay.com , search Real Gaskets Tennesse

I put a real Gasket on 8 years ago and have not leaked a drop I even removed it once and changed the thermostat to a high flow (which did nothing to improve my cooling)

MOST IMPORTANT...

FOLLOW THEIR DIRECTIONS AND USE A INCH POUND TORQUE WRENCH!!!!

 

[harrisonm]

The best way is to toss it and after making the surfaces flat and clean, get an o-ringed thermostat housing.

TOTALLY AGREE! I had the same leak. After about a dozen attempts using everything I could thing of, I bought a Billet Specialties Billet aluminum O ring housing. No leaks for about 5 years.

Maybe not proven but I used an 80 grit piece of sandpaper laid flat on my bench and sanded my stock housing. It was not perfectly flat until I did that. No leaks now. I did use sealer as well.

I tried sanding the Housing and manifold surfaces flat using 80 then 120 then 220 grit dry paper on a flat, hard sanding block, then several attempts with different gaskets ant RTV. Still leaked.

i skim both sides with rtv and just snug the bolts. After curing I tighten another 1/8 turn. Surfaces need to be flat. If oring housing you only tighten lightly to compress the oring.

Tried that too. Still leaked. I am not saying that what you and @Kendog 170 did won't work. Maybe I didn't do a good sanding job. All I know is that I couldn't shake the leak until I tried the O ring housing.
I would highly recommend trying several of the ideas posted above. It might work. If not, The Billet Specialties O ring housing will work.

 

[harrisonm]

Mine leaks a tiny bit with a new china gap, new housing, and blue felpro. No sealant. Doesn’t bother me much, I have things higher on the to do list like the heater core that started to leak a little, but I’ll get to it. I’ll try a little sealant on both sides and see if that does it.

I had to laugh at that. A lot of us have a list of 'more important things' that get put off. But it seems that every time I cross through a problem, I add two more.

 

[matthon]

If the inlet is chrome throw it out.

I just wire wheeled both sides, a little bit of rtv on both sides, gasket, done, no leaks.

In my mind, the pitted metal helps hold the rtv in place and it can't squeeze out.

 

[Dana67Dart]

Another thing to check for is gunk in the bolt hole.

Clean it out and run the bolt in without the housing in place. You should be able to run it in till the head of the bolt has less distance to the manifold than the thickness of the t stat housing.

 

[65 Cuda 340]

Yall are makin this way harder than it is. As usual. Just get the thermostat housing sanded flat and then use a light coat of RTV on the intake to cover the pits and put the gasket on. Oh happy day.

Some of the factory thermostat housings are thin cast metal of some sort (pot metal? aluminum?), and after several removal and re-tightening cycles, they will warp, and then they leak.

More recent chrome housings, same deal. (The old chrome ones were fine. The one on my Hemi has been there since I rebuilt the motor in 1985, never leaked a drop. Newer ones are garbage.)

I have a really thick new aluminum housing on my 413 and it doesn't leak.

And the reproduction cast iron housing on my 340 doesn't leak.

Even a bit of pitting won't cause a leak if you use gasket cement. Important thing is a flat, unwarped surface and a housing that is rigid enough that it won't bend even a little bit when tightening down the two bolts holding it on. If it's anything less than dead flat once bolted on, it will leak no matter what kind of cement, sealer or whatever you use on it.

 

[Icetech]

Aviation sealer.. very thin on both sides of the gasket... it will not leak... ever....