Sealant or not?

Randy

Well Known Member
Supporting Member 3
#1
Today I decided to replace the thermostat gasket because of a small leak from it. Drained the coolant, proceeded to remove the housing. I cleaned the intake surface and the backside of the housing because of some pitting. Then I installed a new gasket and used a sealant. Got everything back together and started it up. Leaked more now than before, so I tightened it up a bit ,that made no difference, still leaked.
Should I use a sealant or not? I ordered a new gasket and a new housing because of the pitting. If I use a sealant, what should I use, the blue silicone or what. I do not remember ever using a sealant, just the gasket.
Thanks
 

Jim Sullivan

Well Known Member
Supporting Member 7
#2
If the thermostat housing and the gasket surface on the intake are both perfectly flat with no pitting I would not use any sealer. If there are any imperfections, I would use a thin bead of Ultra Black(blue or gray) silicone sealer.
 

wristpin

Well Known Member
#3
Is it cast iron or aluminum or chrome?
Lightly run seating surface of housing in circles on 400 grit sandpaper to level it. Use FORM-A-GASKET No.1 which is fast drying and hard setting. After lightly snugging housing down let it sit 30 min or so then torque to 20-25ft/lbs.
 

Randy

Well Known Member
Supporting Member 3
#5
Is it cast iron or aluminum or chrome?
Lightly run seating surface of housing in circles on 400 grit sandpaper to level it. Use FORM-A-GASKET No.1 which is fast drying and hard setting. After lightly snugging housing down let it sit 30 min or so then torque to 20-25ft/lbs.
The intake is cast iron. I just ordered a new gasket and a chrome housing, along with a new thermostat. That old housing was really shot, pitted beyond repair. It's been on there for a least 20 some years.
 

wristpin

Well Known Member
#6
Getting chrome to seal is a pita. If it has the O-ring in seating surface that helps. If it's just a flat surface put that form-a-gasket on the chrome ond let it harden...then put form-a-gasket onboth sides of gasket and block surface. Snug.....let dry....torque.
I get anal about leaks.
 

Ishiftem

Well Known Member
Supporting Member 2
#7
You could put the one you have now on with the Right Stuff. It will never leak even if it is pitted bad. The bad news is that you will probably have to beat it with a hammer if you ever want to remove it!
 

blkblk63ss

Well Known Member
Supporting Member 5
#10
I bought a chrome one years ago and it leaked ,had the o ring. Bought a plain one for that engine. Had the chrome one in drawer for years decided I would try to use it again on another engine. Sanded it on a flat surface with sandpaper ,and it was definitely Warped.( Would not hurt to check intake also with sandpaper and a block of wood.) High on the bolt holes ears low on inner . I then use per matex number 2 ( think 2) smear on intake install gasket remove o ring and fill in with permatex and smear complete surface . . Snug it down and do not fill antifreeze till next day. No leaks .
 

Randy

Well Known Member
Supporting Member 3
#17
Got my new housing today. I filed and sanded the housing's surface, sanded and filed the intake too. Applied black silicon sealant on both sides of the gasket and bolted everything down to 20lbs torque. The silicon manufacturing said to bolt everything together before it dries. Now wait 24 hours. If this fails again, I going to use my cork gasket material to make a gasket. With no sealant and not having to wait for it to cure. I had one on this car that I made 30 years ago, just recently started to fail. I miss that simpler times !

Update: success, no leaks, topped off coolant and ready for the road. Thanks for all the responses, they are greatly appreciated.
 
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floyd

Well Known Member
#18
Great job!If you read the directions on most silicones they 24 hours to fully cure?What happened to the old blue stuff?That stuff never leaked.Todays
stuff sucks,didnt know you had to gorilla glue everything.
 

Junky

Well Known Member
#19
Great job!If you read the directions on most silicones they 24 hours to fully cure?What happened to the old blue stuff?That stuff never leaked.Todays
stuff sucks,didnt know you had to gorilla glue everything.
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