Kevin Mason

Ever since I put an aluminum manifold on, I have had a constant problem with a leaking thermostat housing. I have changed seals and housings, but the thing keeps leaking!

This is driving me nuts!

What is the problem?? The only thing left I can think of is that the manifold surface itself need machining and/or repair. Or I just replace the stock cast iron maifold and forget it.

Sharky Guam

If you are using a gasket, then one of the machined surfaces is out of whack. Sand the surfaces smooth and clean them up before reinstalling the housing. Simply use an RTV type silicone sealant and give it a chance to set up before tightening the bolts. The bolts need to be just pass snug and not overtightened. Don't give up on the aftermarket manifold.

79-L-82

I had the same problem when I got my vette.
It had an old chrome neck on it.
The previous owner said that it leaked and he put a new gasket on it.
It looked new.
I took it off and inspected it.
It was ever so slightly warped.
I bought a new chrome one. The newer ones have a groove and an O-Ring.
No leak since I put that one on.

Hope this helps.
:thumbs:

shoptek

Had the same issues!
Felpro makes a NICE gasket with a seal built right in. It is reuseable as I recall. If I find the part #, I will post it.

Super Stock

I cut out and stamped about 50 h2o pump housing gaskets out of a sheet of gasket material that were a little thicker(before o rings). I have used them on everything from my race cars to pickups. They make good Master cyl. mount gaskets also .Have you evenly spread RTV on both sides . Like Eddie, I pretty much went to straight RTV and have never experienced a problem (even w/ sheet metal manifolds) I can through a couple in an envelope if your interested.

biggjimm

If by chance you are using a chrome housing and or chrome bolts, clean the chrome plating off of the bottom of the housing and off of the bolt threads. I have had to do this on about every engine I have had with chrome goodies. Good luck. Biggjimm

Vetterodder

Are you using a stock housing or one of the chrome after-market ones? Most of the chrome ones are made of cheap pot metal and corrode quickly, making a good seal impossible.

SHAKERATTLEROLL

If you have one of those purty chrome ones find a nice place where you will not hit anything and throw it as far away from you as you can. :). And get one of the old cast steele housings which are still around through chevy or Zip. Take a good file and run it across both surfaces to make sure they are flat. Then use your favorite gasket and RTV to fill any voids. When you do use the RTV just put a little on both sides and let it skin for about ten minutes before you put the parts together then snug and you are living large with nothing leaking. :)


[Modified by SHAKERATTLEROLL, 5:39 AM 5/24/2004]

Kevin Mason

To everyone: thank you for the advice!

To answer some of your questions: I am using a new stock housing.
Nothing chrome, aftermarket, or purty. Before mounting, I kissed the sealing surface up with a stiff sanding block to make sure that there were no high spots. I used a bead of RTV on both sides, allowed it to dry beforeinstalling the thermo housing. I was careful not to over-torque to bolts.

The only thing I can think of is that the manifold sealing surface is somehow damaged. Maybe one of the Felpro gaskets would help?

Still frustrated.

Fevre

Did you use RTV on both sides of the gasket? And did you let it dry before putting the housing on? You need to apply a thin bead to both sides, put the housing on and snug the bolts up, let it dry then torq them down. Also are the bolt holes taped into the water sleeve? If so you will need thread sealer on the bolts.

Matt Gruber

also check the thickness of the 'stat
and the depth of the recess

Kevin Mason

Fevre (why do I think you must be Brett Farve?) and Matt:

RTV on both sides - check.

thin bead - check

let RTV dry then torque down - check

thread sealer on all bolts - check

All I can think of is that the manifold surface is uneven somehow, but keep the suggestions coming.

Fevre

Any chance there is a hairline crack in the intake or housing? Sounds like you did everything to make it seal. :confused:

norvalwilhelm

I true up all my thermostat housing. After being overtightened they warp down at the bolt holes. Take a sheet of emery paper, 8 by 11 works fine and tape it down to a flat surface, then draw the housing over the surface in one direction only, NO back and forth motion. Take the housing , put it at the top of the sheet and slowly draw it towards you while holding it down firmly on the paper. Make a few passes, check for pattern, you are looking for the high spots to be marked by the emery paper, keep going until the bottom of the housing has a complete pattern over the entire surface.
Never push it back and forth , it will only round the surface.
Pull it towards you , lift, start at the top again, pulling and pushing down to hold it flat.
It only takes a few minutes to flatten the surface.
Do not OVERTIGHTEN.

Sharky Guam

Well, if you tried everything that was mentioned and rtv does not do the job, then perhaps we are overlooking one important piece. Did you check if there are sufficient threads on the bolts and on the manifold to allow the parts to be tightened together properly? Clean the threads on the bolt and the manifold. Put the bolt on the manifold without putting the housing on. Turn the bolt in and see how far it goes before it stops. If it goes all the way down past where it should be when the housing is on, then you are okay. If not, you need to run a tap thru the threads in the manifold. Or if the bolt has enough threads running in the manifold, you could simply put a flat washer on the bolt side of the housing as a spacer.

The water pressure is not that high, so we should be able to easily fix this problem.......rtv does wonders on most water leaks......

Kevin Mason

Sharky and Norval:

I already tried truing up the surfaces of the manifold and the thermo housing using sandpaper stapled tight to a flat wooden block.

Threads in one bolt hole were bad, so I helicoiled them, which eliminated that mess.

Finally, I realized that the bolt was bottoming out - Sharky had the right idea - so I added a washer and so far, no leaks, knock on fiberglass.

I was starting to wonder whether this sort of thing was chronic to SBCs with aluminum manifolds, and, if so, why noone bothered to tell me.

Sharky Guam

I was banging my head trying to figure that one out. My dad once said, if you can't figure a problem, go back to the simplest solution and start there. It looks like that was the key.....

Congratulations! Now go and enjoy that vette.......

ZD75blue

I've always just taken a file to ones that have a little meat to spare...

Run it over the length of it a couple times and it shows you the high/low spots... make em all the same and it should do you well! (I'm to lazy to use emery paper... take the heavy cut stuff!)

Although this method probably wont help if you are trying for a perfect fit... it has helped a couple of stockers over the course of time! :cheers: