leaky thermostat housing 2000 3.8

[northern piper]

So I've been trying to track down a minor (but annoying) coolant leak on my 2000 3.8. Coolant always seems to collect as a result of this leak just under where the brake pressure sensor is. There is a little fin on the block which creates a reservoir that'll hold 1/2 ounce or so. Anyway, I've come to realize that the thermostat housing at the bottom is leaking slightly. Yes there is a gasket and the bolts are torqued to the correct value and the t-stat is in the right way. Has anyone ever had the housing be not flat? When I redid the coolant about 2 months ago I sanded the housing as there was evidence of a bad casting. It just pisses me off that I have to do this and loose all the coolant in doing so. Do people use a gasket sealant here or just the gasket? Ford says to only use the gasket but I'm beginning to wonder.

Piper

[12Ounce]

I've had the same misterious/annoying leak for a long time. I assumed it was my own poor workmanship as I had replaced the thermostat "way back when". It can be a tough area to reach. This last time, during overhaul, I made sure mating parts were clean and properly located, and I used a thick paper gasket lubed with petroleum jelly (my practice). It seemed to seal-up OK this last go-round.

However, the reused thermostat is opening too soon to suit me ... the engine is slow to warm up. So I will be doing it all over again.

[tripletdaddy]

I spoke to a mechanic friend of mine who said that because gaskets historically have given problems as they age. They will dry up, shrink and crack allowing a leak. He said the new assembly practice is no gasket at all and just use RTV sealant. I didn't know Ford said NOT to use any sealant on the gasket or metal surfaces. More often, I have read across several different manufacturers to use sealant to at the very least to aid in holding the gasket in the right place. In your case, I wouldn't hesitate to use a sensor safe sealant.

[northern piper]

Ya, I think I'm going to have to use some sealant. I find that my local Ford parts/advice is unreliable. There is 1 guy there who used to be a mechanic who has never lead me wrong. The 2 other guys will "advise" you but their advice always seems to have some bugs.

The Ford gasket is about as thick as 2 sheets of paper. Is there a better gasket or material I could use? I'd love to get some 1/16" thick cork or something in there along with the gasket sealant I'll use now.

Piper

[12Ounce]

My thick gasket came in the engine overhaul gasket set, I believe.

You could also just use a "stack", two or three perhaps, of the thinner ones. This should take care of a great deal of surface irregularities.

I find that petroleum jelly on water hoses and water gaskets is a lot more forgiving (less clean-up) than other sealants when it comes time to "go back in".

[tripletdaddy]

I've seen at least two types of cut your own gasket sheets in a roll at the auto parts stores (Advance and maybe Auto Zone, Napa and Carquest I'd expect too). One was a heavy weight paper or light weight card stock, and the other was a thicker cork. Maybe if you had a beltsander, you could get that tstat housing more flat.

12ounce, I like using the p jelly too for hose and similar assembly for later removal, but I never considered it for gasket surfaces. Cleanup and removal would be easier, I'll consider trying it, but I'd still rather use RTV on poor mating surfaces.