FMS Thermostat housing


Founding Member
Aug 24, 1999
Norwalk, Ohio
Any one installed Ford Motorsports 90 degree thermostat housing with the sensor housing screw on the top?

Just installed mine and just by filling it it leaks around the screw. I used teflon tape so I assume something else is not quite right. Did these have gaskets for the screw?

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Dave, you are far from the first to experience this. THe solution for many is to sand the chrome off around the hoses (that seems to be a source of leakage), but it doesnt sound like that is your issue.

Did you use a gasket? Some gasket maker might be in order. I would use a flat-edge (machinist's edge) to make sure both surfaces are plumb too.

Good luck.
removing the screw and putting rtv sealant on the threads will fix the leak. it will probably continue to leak from everywhere else though. i painted my stock housing aluminum and put it back on after getting so frustrated with the FMS part.
Before reading this I was thinking about sanding and polishing my stock piece....sounds better all the time.

Ironically it leaks and I haven't even started the engine, so if the chrome promotes leakage, I shudder to think of what may happen when theirs pressure.

One previous comment mentions a gasket....on the screw. It seemed logical to have one there, but I wasn't sure. Is that what the reference was to?

I only use Felpro gaskets since I have had the best luck with them. I always let the gasket tack set up and work slowly to avoid those irritating leaks at the manifold.