Thermostat housing

[wlewis]

My 351W's thermostat housing is leaking again. Several years ago, I replaced my custom made steel surge tank that leaked, with the Finishline welded aluminum tank. The Finishline tank included a cheap, chrome thermostat housing that was slightly warped. After filing down the housing, I installed it with included O ring and leak stopped and everything was fine......untill recently when leak started back. After disassembling tank, the housing warpage is worse than before. Even though a new O ring is thicker than the housing groove and would probably eliminate the leak till the O ring flattens, I would prefer to use a heavier duty thermostat housing. I ordered a stainless steel housing from Summit, but returned it because the neck was about 1/2" too long. Neither Summit nor Jeggs offer any other stainless or billet aluminum housings that will fit a 351w. Anyone have any suggestions as to who might have one available?
Walter

[Jim Harding]

Walter, are you sure where the leak is? I've seen more leaks around the bolts due to not using a good sealer on the bolt threads. Those bolt holes in the intake are not blind holes. They go all the way through into the water passages.

[wlewis]

Good thought, Jim. All I really know, is coolant drips from manifold/thermostat housing connection joint and drips onto top of engine cover. I've never considered the bolt holes as the leak source, but I did plan to using a sealant in the bolt holes when I put it back together. Thanks!

[Jeff]

If you have a flat sander reserface the bottom and put your o ring back in and then use 100 percent rubber silicon and put on the bottom of housing tighten down let dry over night then put your fluids in the following day should have fixed problem. Jeff

[diegokid]

The "ultra" type silicon is more water, gas and oil resistant than plain silicon so try it instead.

[cal.cheesehead]

Permatex makes a water pump and thermostat housing rtv silicone. Mine leaked. Used this product.. no leaks..good luck.

[Jeff]

All the answers are right but I have had very good luck with just clear slicon but I think they all will work as long as there is no gas there any of them should do. Jeff

[Aggressor]

I agree that the waterpump and thermostat housing product makes a better cooling system seal.

-Geary

[JeepSnake]

And on the silicone sealer:

Read the instructions on the package, and follow them to the letter. Generally, they will tell you to put the sealer on, let stand for 5 - 10 minutes, then assemble the parts, tightening the bolts finger tight. Then, let stand for another 1 - 2 hours before fully tightening. Finally, wait at least 24 hours before putting liquid into the system.

On the AMC 258 in my old Jeep, the valve cover would leak like crazy if I deviated from the RTV sealer instructions at all. I mean, the method had to be perfect!

One other note is that I always clean sealing surfaces with a lint-free cloth and acetone just before applying sealant. Helps make sure that there's no grease or coolant contamination.

[Jerry Cowing]

A problem I discovered on my 428 leaking thermostat housing was the bolts were too long. Consequently, even though I torqued them to spec, they kept leaking. When I finally measured the depth of the hole in the intake manifold, plus the thickness of the thermostat housing, and compared it to my bolt lengths, I discovered the problem of too long of bolts. Replaced them with shorter bolts and have had no problems since. With older rebuilt engines, you never know if they replaced the bolts properly during the rebuild or during previous owner repairs. Many builders throw all the bolts in a pan to wash them and then grab what they need out of the pan during the re-assembly, so they often grab the wrong bolts.

[wlewis]

For lack of availability of anything else, I used a new chrome housing and O ring. I used a thread sealant in the bolt holes even though they appear not connected to water passages and torqued them down at 13lbs. No leak, but like last time, I don't know how long it will last. I do think last time I might have overtorqued bolts which may have compromiseed the O rings. Time will tell. I also used clevis pins with cotter pins, rather than bolts and nuts to fasten hood hinges so next time I can at least remove the hood easily and quickly!