Leaking thermostat housing

[rrunnertexas]

This problem is driving me crazy! How can such a simple thing frustrate me so much?

I need suggestions on how to seal the thermostat housing on my 383. I can't get this thing to stop leaking coolant!

I have a new MP aluminum water pump housing and a MP heavy chrome t-stat housing. I have used several brands of gaskets with sealer and every time it leaks!

1) Ultra black silicone w/gasket - Leaks
2) Brown form-a-gasket #2 w/gasket - Leaks
3) Ultra gray water pump silicone w/gasket - Leaks

I have also tried using a new cast iron t-stat housing that I know is flat - Leaks.

It appears that the water is soaking the gasket and the water leaks through the gasket.

I have placed the t-stat housing on a flat bench with some sandpaper and cleaned the surface.... It appears reasonably flat.

What sealer should I use? Should I omit the gasket altogether?

Ideas?

P.S. I have had bad luck... I had the same problem with my factory iron water pump housing too!

Thanks,
Dave

[cudabob496]

Save some headaches and put some bars-leak liquid aluminum coolant radiator sealant in your cooling system. I've used it for header bolt leakage and all kinds of stuff on my 496 Cuda. Just little tiny pieces of aluminum that seal the leak.

[wilks3]

Take your thermostat to the parts store, have them get one of the rubber seals that will fit over the stat. The seal has a slot the stat fits into. Find somebody with a lathe, center the
housing in the chuck. Machine the housing so the seal fits in, its new O.D. in the housing. Cut the depth so the seal is half way in and half way out of housing. Bolt it back on. Done, forever. It takes longer to get new seal and find lathe than it takes to machine new flat groove that the seal sits in. I hope I explained this ok.

[BigBlockDude]

A felpro gasket and a nice bead of RTV has always worked for me. Don't fill it until its dry, at least a day.

[rrunnertexas]

Every time I have tried this I wait 24 hours for the sealer to set before adding water/anti-freeze back into the system. So, it does have plenty of time to dry.

Can I just put some sealer in the area and forget the gasket? Does this work?

Chrysler must of figured out a better way since the factory just used a simple gasket without any sealer, correct?

[jelsr]

SWAG Could your bolts be bottoming out in the casting and not compressing the gasket properly?

[70Ted]

its the crap chrome housing, they all leak.

[dirttrackracer]

Seeing how you have all those gaskets around try doubling up the gasket.Put just a lite coat of sealant on all sides of the gasket. make sure the t-stat is seated properly in the recess in the t-stat housing. That sealant only needs to set for about 15min then assemble the parts. then fill her up with water and check for leeks. if you got it drain the water out and put the antifreeze in.
It's quite likely that the t-stat is NOT in the housing correctly that is causing your leek. Good luck.

[OHD]

I can send you a piece of Chesterton 140 gasket material for you to make one.

I use it for just about everything from intake to oil pans on our engines. Never had a leak with it for 30 plus years...on waternecks.

PS: orings work the best..

[rrunnertexas]

The bolts are not bottoming out in the pump housing since the MP aluminum housing has bolt holes that are straight through (no bottom).....

I had the same thought about the chrome housing being crap as well, however, I replaced it with a known flat cast iron unit and had the same leaking problem.

I just finished installing the housing again using plan "b"... oopps, in this case plan "g" or "h". I purchased some of that gasket sealer in the pressurized can called "The right stuff". I followed the directions and installed it without any gasket at all, just the sealer. I will add water tomorrow night and see it it leaks.

[cudabob496]

Coat the threads on the bolts with pipe thread sealant. White pipe thread sealant on header bolts works great too.

[Dick]

Originally Posted by rrunnertexas

The bolts are not bottoming out in the pump housing since the MP aluminum housing has bolt holes that are straight through (no bottom).....

BINGO! If the bolt holes go right through into the coolant cavity, you're getting capillary action up the threads, aided by the pressurized system.

Use sealant on the threads. That should stop it.

[bbeckwith]

If the other methods fail to seal up your leaking problem, you can buy new waternecks with an o-ring installed, like the chevy guys use. They can get a bit pricey, but the one I got has not EVER leaked, and looks good as well. Check out moparsbycrane. I believe they have them. If not, I will get you a link to one somewhere else. There was the guy who said to get a machinist to cut a groove for an o-ring, if you can get it done for less than around $50, go for it.

[TrashedCharger]

Originally Posted by 70Ted

its the crap chrome housing, they all leak.

Nail on the head.

What's up with everyone running silicone on these gaskets?? I haven't used silicone on any gasket for several years now and I have never had a leak. Pipe dope on the threads on a water pump and thermostat housing. That's it.

Just use a cast housing, a good gasket, clean the surfaces with a razorblade (bending the backing, arching the blade usually helps clean better) And tighten the bolts. I have never had a problem without silicone.

The chromed steel housings will bend under the tension from the bolts. They are worthless.

[Dick]

Hasn't anyone picked up on the fact that the bolt holes in the waterpump housing go all the way into the cavity? That is where the leak is from. Seal the bolt threads, stop the leak.

[rrunnertexas]

I should have been a bit clearer when I said the bolt holes have no "bottom". They are not in water... they are open holes on the outside of the housing, so there is no chance of water leaking up the theads.

THANK ALL OF YOUR FOR YOUR GREAT IDEAS AND HELP!!!!!!

UPDATE: I re-installed the heavy MP chrome t-stat housing and did not use a gasket at all. I used a gasket sealer called "The Right Stuff" that comes in a pressurized can. I applied sealant to the t-stat housing and bolted it back in place per the directions. I allowed it to dry overnight (not necessary) and then added water. Fired up the motor, drove it for an hour and re-checked.... NO LEAKS! It is a miracle!

I attached a small sized jpeg of the final assembly.

[Dick]

Nice and clean. Looks good. Any other shots of the motor or car?

[PistolGrip440-6]

The chrome does suck. My GTX had a Mr Gasket one (a real one, nice and thick) on it and I couldnt get it to stop leaking. Three times, no dice. Took the housing off figuring maybe it wasnt flat, this thing was warped beyond beleif. Probably 25 degrees off. My old mans a mechinest (haha gotta mess with 'em when theyre older) so he milled it for me, which also took off the chrome around the bottom which I suspected may have made it harder to seal. Just used a paper gasket, no leaks. I just did this over the weekend.

Anyway, the reason I brought all of that up is do you guys think that having the chrome on the housing itself where it has to seal makes it worse because it makes that surface smooth? I know the chrome ones arent as good but I always assumed it was because they just aren't as tough and tend to warp easier.

[TrashedCharger]

I'm glad that you solved the problem. If you have a chrome housing, just keep an eye on it. I think the reason that they leak has more to do with their construction and straightness, rather than the polish level of the sealing surface. Look at the level of grit that is used to mill a turbo engine block and head for a metal head gasket. They are almost completely polished and seal better than a coarser cutting stone with a regular head gasket. Polished surfaces will actually seal better under higher pressure situations, but the construction of the mating parts needs to be rigid.

Dick, I would always suggest using thread sealer on any water pump or thermostat housing bolt, all the way up to the head. Another thing you can do on them is install allen plugs down in the bottom of the hole and use a shorter bolt to attach the housing. If you do this, you need to use loctite on the short allen plug. It can't be plumbing thread, either. Just a grom screw with loctite. The plumbing thread plugs will not go down inside the hole and if you don't use loctite on a dry surface (preferably before the manifold gets installed), you run the risk of having it fall out in the bottom. The short grom allen screw at the bottom of the hole with loctite works the best of all. It won't hinder the bolt keeping the housing, as long as the grom screw is short. Sometimes it's best to grind and file them shorter than they come. As long as you have as much thread area contacting in depth as wide as the bolt is in diameter on any bolt, you are fine.