Need help. Thermostat gasket won't seal

[workman13]

Ok I decided to change my thermostat today. Took it out and put the gasket on and put it all back together and put some gasket sealant on it. Started adding coolant and it started leaking alot. Took it off and didn't see anything weird with the gasket but I decided to buy another one.*
Once again put a little bit of sealant on and let it set for a couple hours. Went to add more and once again its leaking. Does the gasket go on the side against the engine then put the thermostat against that and put back together? Any ideas or advice?

 

[jworth]

I'm thinking the gasket goes on the head side of the thermostat though I'm not sure about that. Whichever side the thermostat is on is recessed for it. I do remember I had some trouble with mine once. I got looking at the thermostat housing and noticed that it wasn't particularly flat or smooth. I worked it on a very flat board covered in fairly fine sand paper to give it a nice smooth finish. Worked for me. Good luck.

 

[md21722]

If the housing was ever tightened when the thermostat slipped down out of the head there is a good chance the thermostat housing is warped. You can try to flatten like worth suggested, or buy a replacement. They are not expensive, $7-15 at NAPA.

 

[Hypoid]

Thermostat rests in the water neck, gasket goes over that. I use a tacky sealer that holds the gasket and thermostat in place while I install the water neck. If the thermostat slips out of its recess, you will have a leak. If you tighten the crap out of the water neck at that point, you can crack the water neck.

 

[Devilfrog]

I don't even bother with the gasket these days. Thermostat goes in head. I use a bead of RTV grey or black, smear to an even thickeness and hand turn the bolts. Wait 10 minutes then torque, wait 10 minutes before adding coolant. Both my water pump and thermostat housings are done this way, on both my 00 XJ and my 88 MJ, never had a leak. Key is don't go overboard with the stuff.

 

[Talyn]

It goes head --> t-stat --> gasket --> t-stat housing. Make sure the t-stat is seated correctly and doesn't fall. Torque is 15 ft lbs

 

[dcampbell98XJ]

When I replaced mine I had the same problem, cleaned everything and when I filled it it started leaking. Took it back off and realized the housing had some slight pits on it. Replaced the housing and haven't had a problem since.

 

[Digger87xj]

stop using sealant. put the gasket on dry. It will swell when the water hits it and seal up.

 

[Original_MudButt]

^^^^ That's how it's supposed to work. I just put a very small/thin dab of permatex #2, about the diameter of a pencil eraser, in 4-5 spots to the gasket where it mates with the housing. Slap it on and set it aside for 15 minutes or longer.

All that does is hold the gasket in place so it doesn't get pinched when installing the housing. The swelling of the gasket does the rest.

 

[Shorty]

It goes head --> t-stat --> gasket --> t-stat housing. Make sure the t-stat is seated correctly and doesn't fall. Torque is 15 ft lbs

^^^^ That's how it's supposed to work. I just put a very small/thin dab of permatex #2, about the diameter of a pencil eraser, in 4-5 spots to the gasket where it mates with the housing. Slap it on and set it aside for 15 minutes or longer.

All that does is hold the gasket in place so it doesn't get pinched when installing the housing. The swelling of the gasket does the rest.

follow the two posts above and look for cracks or warping if it continues to leak-- there's nothing "special" about Jeep water outlets vs other vehicles. It's a matter of cleaning things well and getting things aligned in the proper location.

 

[8Mud]

The only trouble I've ever had is, every so often one would seep around the bolts. I'm thinking the right bolt, but I could be mistaken. It has been twenty years, I always use LocTite on the bolts now or in a pinch, a dab of silicon on the threads.

I put a really light coat of silicon on both sides of the gasket. Three reasons, to allow for scratches that might cause issues, to help hold the gasket in place during assembly and believe it or not cleaning off the silicon the next time is easier than getting baked on gasket off of there. The impregnation they use in most gasket material can be rough to get off sometimes.

I've had one leak, my son used the wrong bolts and it looked like it was up tight but wasn't.

Put a sheet of 220 sand paper on a board and take couple of swipes with the thermostat housing. The flaws will show up quick. A few more swipes with some 400 and your ready to install, unless the flaws are major.

I once pulled a thermo housing off and the last mechanic had put so much silicon on there it had spread in with the thermostat and was gumming the works up, A really thin coat, just enough to seal any possible scratches that may pass coolant, is enough.

 

[iwannadie]

I had a problem leak years ago that was driving me nuts.

It turned out for me, that there was some coolant trapped in the head even though I had let it all drain out there was enough in there to cause a problem. What I think was happening is the coolant trapped inside was just enough to seep out(wicking effect) and cause it not to seal.

I soaked up the coolant trapped in the head so it wasn't close to the thermostat opening and had no problem after that.

The next time you do it just to be sure I would soak up the bit of left over fluid in there just to rule that out.