The thermostat housing gasket leaks on the 440. It had a "plastic" one and it leaked. Then I put a "paper" one on it, and it leaked as soon as I topped off the radiator! So.....for try number three, what is a sure-fire way to prevent that thing from leaking? (the first one had black RTV, and the second had Permatex Super Weatherstrip Adhesive) Any advice would be appreciated.

My cheap Chinese chrome housing leaked until it was replaced with a Mancini Billet and blue gunk. Mine leaked at a car show. Really pissed me off. Good luck.

The MP unit warps. If you pull it off and put it on a flat bench, I bet you will see it visually. There is no pint in trying to mess with it... if you sand or file it flat and re-install it will just warp again. Been there and so have lots of others.

To fix, get an iron or billit aluminum neck. The inexpensive iron ones stocked by most parts stores work fine or Mancini and others sell a billet version. Check flatness of the neck and mating surface on the water pump. Sand or file flat if needed. Then install with a little Locktight #1 and a paper gasket. Be careful not to overtorque as this can warp the neck and cause a leak. Last step... pitch that chrome water neck as far as you can.

Those chrome housings are junk.

Drawfile both surfaces to get em flat w your finest grit wide/flat file

I have an old Mr Gasket chrome on my 440.No leaks with a good gasket.Id lay some sandpaper on a flat surface and sand the housing the use a small piece of wood and sand the pump it self to make sure they are both flat.The 3m dosent seal just keeps the gasket in place.Rocky

I run the thermostat housing on a belt sander,you would be surprised how they warp.With a square surface and a "good" gasket you don.t need any sealer.

Thank you all for the input! I will drop that chrome piece o' sheite in the garbage. Can hardly see it anyhow once it's mounted; I got A/C.

As others mentioned, block sand it flat as they always seem to be warped. Also mentioned, some adapter housings are just junk. If you dont want to replace the housing or need it fixed ASAP, run over to your local parts store and get some Permatex Aviation. I've been using this stuff for years at my shop and its never let me or my techs down. No matter what the bottle says, theres basically no rules with this stuff, within reason:-). I would just make sure the surface is dry and clean. You can use or not use a gasket. The only downside, once its sealed up you cannot reuse any gaskets and you may need to use a roloc disc(scotch bright roloc,cookie ect) and the more aggressive brown to clean the surfaces next time. I've never had an issue with this stuff sealing, even in some bad surface areas, as long as everything is clean/dry. Its approved for aviation which says it all. Let me know if anyone else uses this stuff.

One more thing, let the stuff set up a bit before filling with coolant. Not a super long time but a good 15/20 minutes. The longer you wait the better.

I should of mentioned, make sure any RTV is cleaned off real well. It would be a good idea to use a lite roloc (gray disc) on both surfaces first. If roloc disc's aren't available lightly use some emery cloth or fine sand paper.

Yes the chrome one are trash period i put a stock one from advance auto that cost 6.00 dollars with the gasket. worked perfect.! Make sure the gasket goes down first and the the stat and then i used The gasket sealer and have had no leaks at all.!

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Those chrome housings are junk.

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What he said! I pulled the leaking junk chrome housing and replaced it with a used stock piece, and haven't had a leak since.

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Block sand it and clean the manifold with a razor and then get some good old fashioned permatex silicone sealer apply evenly and not below 50 degree's once done snug bolts and let sit for hour or so and you will be good to go I don't even use gaskets the key here is make sure the silicone sealer is set up and on a clean surface. I do this up to 12 times a year and only have a goof once in smurf blue moon

As others have said it needs to be flat. I had the same problem and I put the housing on a belt sander and sealant on both sides of the gasket.

I had less luck with local parts store oem one than I have with thick chromed one. The oem from parts stores seem to be so out of round that even if I got the mating surface flat, the hose neck was so mal-shaped I couldn't get the hose to seal.