To Hell with the FMS thermostat housing!

I have heard a few people had leaking issues. You can use diesel silicone (grey), that might solve the problem. Apply a thin layer to the intake and a thin layer to the housing, let sit for a little while until it starts to dry slightly, then put the housing on.

I sealed an external waterpump housing like this and it hasn't as much seeped a drop in 5 years.

1. Put a small amount of RTV on the edge of the themostat, place it in the housing and let it set up for a few hours. This will keep the t-stat from moving when you install the housing. (this is the reason for MANY leaks... if the t-stat shifts, it will cause a gap and a leak is certain)

2. Spread some RTV on BOTH sides of the gasket.

3. Install the housing and draw the bolts down a little at a time going back and forth on each one so you don't warp it.

Do it this way and you'll never have a leak. Stop blaming the housing... I've yet to have a leak with any of the housings I've used (chrome ones too) and I've been building engines since I was 18 and I'm 42 years old.

Polish the stocker

I've heard tons of horror stories about those chrome ones for some reason, and I'm glad I was always too lazy to get one before I started hearing those stories.

I did an intake swap once and was 20 miles from home and had to drive my car home...it was late at night and i didn't have any gaskets, just RTV. I got desperate and cut out a gasket from a Coke 12 pack box. Used RTV on both sides and on the inside edge of the thermostat.


It's been on there for a good year now with no leaks

I think it was Daggar that recommended to me just taking a drop or two of Super Glue to the thermostat to hold the thing in place while you're fiddling around with the gasket. Sets up a helluva lot quicker than waiting for HOURS for RTV to set up and cure.

In the past, I've always had luck with simply putting the T-stat into the housing, then sliming some RTV on there, pressing the gasket onto the housing (making sure the bolt holes line up, of course), and waiting about 30 minutes so it stays tacky enough to hold the gasket in place fairly well while you manipulate the little turd into position. Not as exact or reliable, but again, it's always seemed to work just fine for me. (Although I now prefer the Super Glue trick. )