OldRide Answers Home
Using OldRide Answers
Ask a Question
Browse Questions In:
Other Makes
Classic Trucks
 General Topics
General Questions
Help Identify
Classic Car News
General Restoration
Vehicle Maintenance
Site Suggestions & Comments


Ask a Question in OldRide Answers
Help Enrich the Classic Car Community
Explore Closed Questions and Answers
 Search Questions: 
Can't get coolant to stop leaking around thermostat housing.
Hey, I'm just learning to work on cars. I'm working on a 79 Mustang with a built up motor and it's leaking coolant at the thermostat housing. I have put in new thermostat and gasket and it is still slightly leaking around lower left side of housing. Any suggestions on how I get this to stop?? Thanks ahead of time for any help.

Peace and God Bless,
posted: August 26, 2011
  Answers (4)
I would recommend starting over with a fresh gasket! A.) use a putty knife or razor scraper to clean both the thermostat housing and the block or intake side receiving the housing. B.) Use a clean rag or paper towels lightly soaked in paint thinner to wipe both sides/pieces. C.) Inspect closely for any cracks or residue which wasn't removed. D.) On your new gasket spread A LIGHT BEAD of permatex on both sides of it. E.) Drop in thermostat, replacing housing and start tightening bolts until a small amount of permatex squeezes out.. F.) Allow to dry for a couple of hours and you should be good to go!!
posted:  August 26, 2011
Click to close this picture
Thanks, I'll give that a try. I was having trouble keeping the thermostat in the groove on housing (which kept causing leakes because it would slip down) so I used this adhesive the parts store gave me and put some where thermostat goes, placed thermostat in groove, put gasket (with glue) over top of that, and then mounted it. Would that be to much adhesive and causing it to leak? or is asymbling it that way might cause some leaks? Thanks!!
posted:  August 26, 2011
Click to close this picture
If it was an aftermarket thermostat housing, a lot of the less expensive ones are junk, and warp with the first usage, they shouldn't be allowed to sell them. If it is the OEM housing, and you are still having problems, if it were me, I would file the housing base until it looked like any high spots were gone, and everything the base filed consistently smooth from one side to the other. The gasket adhesive should be used to adhere the gasket to the thermostat housing, and shouldn't be used to try to seal up any leaks, that's not its purpose in life....
posted:  September 22, 2011
Click to close this picture
Permatex 2 non hardening gasket sealer.

I never use silicone base gasket maker for coolant applications,have you seen the stuff that oozes out the sides?

Well that same thing happens on the inside,very good for making little worms that end up in the core of your radiator!!

40 years experiance,trust me .
posted:  October 31, 2011
Click to close this picture