carlt66

How involved is it to replace a leaking thermostat housing? - the chrome plated housing that was put on my 66/289 during it's restoration project is leaking when the engine is started and when I shut the engine off - no leaks that I can determine while it runs - I'm assuming that it leaks at these times because the engine does not require coolant and the hose pressure forces the liquid to the closed thermostat and through the gaps in the thermostat housing - how do I contain the coolant if I remove the thermstat housing? - what type of housing is the best to use? - I don't know if I should get another chrome plated one - I was told these often leak - are the gaskets that come with the housing good enough or should I get another type? - also,should a sealant be used in conjuction with the gasket?

Starfury

You need to drain the coolant to change the housing. Most Mustang wherehouses offer a cast aluminum housing, which is what I'm using. It's light and it matches my aluminum manifold. I believe you can get polished housings as well.

When I do these I use a coating of copper spray-a-gasket on both sides of the paper gasket. It's always worked well for me.

69thunder

Most leaks in the thermostat housing are caused by over torquing one side which causes a very small crack. It could be the gasket as well. Drain coolant, take it off and inspect it very closely. If you need a new one there really is not one that is better than another it is a personal choice. Just be very carefull on reassembly. It does not take much to ruin them.

carlt66

Thanks Starfury - I looked up the installation of a thermostat in my shop manual - it conveyed the same basicinfo as you wrote about- the manual saidto to tighten the bolts to specification - however, no specification was given - any idea on what this might be? - do I need to get a calibrated torque wrench for the job? - how tight is tight? - also, do I have to drain all of the coolant? - I am assuming this would be from the radiator! - thanks again.

Nascarl

69thunder

Yes you have to drain coolant from the radiator. It is not just the spec when tightening. You need to tighten one side a little and then the other a little at a time until it is tight. If you just run one side down it is likely to crack. I just tighten mine till I feel like it is good enough. I never have known the actual spec. You should be able to feel it out. Just don't use a breaker bar or 1/2 inch drive and you will be fine.

blue66mustang

Also if you buy a new one PLEASE dont buy the chrome one that uses the rubber "O" ring to seal. I paid $12.00 for a Mr. Gasket one ( funny Mr. GASKET)that I just had to replace real fast. No matter what I did it would still leak.

FWIW.

Starfury

Yeah, I've heard the o-ring housings are crap.

I don't know what the spec is either, but if you've got the Factory Service Manual they'll be in the back of the section you looked up for the install. I usually just torque them until I think they're good and tight. If you've got an aluminum manifold, make sure you don't strip the threads out.

jlg2002

Snug! is the technical speak for tightening in aluminum. It occurs just before S**t, went too far.

stanger53

I read a post about a guy that had the typical leaking chrome thermostat housing, and decided to find out what caused the problem, being as how this was a common situation. He found that the recess in the housing for the thermostat lip to fit into was too shallow, and the lip of the stat didn't sit far enough into the recess. This caused the housing to sit too far away from the intake manifold and wouldn't allow the gasket to seal. It also caused the housing to warp or crack when tightened down because the housing wasn't flush against the surface of the manifold. He put the housing in a lathe and had the recess turned down a slight amount until the lip on the stat was below the mounting surface of the housing. No more problem after that.

carlt66

Hey everyone thanks for the info - I really appreciate it - a few quick final questions about this impending project - I'm all set (thanks to you) on the install - however - I read that the restart and adding of coolant has a process to follow - here's what I got - prior to engine start, refill radiator to about 3 in. below top of radiator - start car - once stat opens trapped air will flow to the cap and "burp" out - the coolant level will rise and overflow the radiator - once the air pocket is out the level will drop - you then add more coolant - alot of coolant! - you then stop at the normal 1 in. from the top - How loud is this "burp"? - and how much coolant will overflow? - I'm envisioning a loud bang followed by a flood of sticky antifreeze - I'm also assuming all this is done with a closed radiator cap - don't mean to be paranoid.

Nascarl