Leaking thermostat housing
 

I have been fighting a coolant leak at the thermostat housing for a few years. I discovered a couple years back that the housing was not flat. I attempted to flatten it on a bench belt sander and it held for a short time. I then purchased a new housing and again it held for almost a year but failed again a week ago.
What is the best wat to seal the housing to the manifold? gasket? no gasket using gasket maker? gasket with gasket sealer?

I like the blue gaskets with the sealer on.

Mostly the whole key is to fight the tendency to want to tighten the piss out of the two bolts if it’s not a cast iron housing, which most are not.

At one point in time the company Everco use to offer for all America made cars the choice of a replacement cast iron or Aluminum T-stat housing, i do not know if they still do.

The Aluminum ones just don’t have enough flange thickness to not warp over time and in terms of this issue the thicker the gasket is , the more and the sooner it will warp, and this is compounded if the gasket is of the type that shrinks with age!
If both gasket surfaces are in great shape then a thin gasket with a swipe of sealer is best!

I have used the blue paper gasket with the permatex aviation gasket sealer with good success.

This is the best gasket I can find nowadays. Most are slotted universal types. This works well and is a quality gasket as you'd expect from Fel Pro. I coat the crossover and the water neck with aviation permatex. Never had one leak with this method. FWIW

This;


https://www.permatex.com/products/ga...-no-2-sealant/


with the blue gasket.


#3, as mentioned above, my 2`nd choice.

My aftermarket aluminum intake with new aluminum water neck seeped. The factory style bolts (one is a nutted stud to hold the alternator bracket) were bottoming out right at the point you pulled them snug so there wasn't enough clamping pressure. I installed 2 full- thread studs and nuts. No more leak.

I have observed that issue on several aluminum Tri-Power intakes with the holes not being drilled deep enough for the bolts used. I use "allen head" studs permanently installed in the intakes these days but for sure not a Car Show
"Correct" fastener. Same deal with the Valve Cover Bolt Fasteners that some say leak water. Permatex on those too.


Tom V.

I use the chrome water neck with the rubber o ring. Zero issues. Also important to ensure intake thermostat housing area is flat and not full of rust pits.