Leak after replacing thermostat

[Wajeep]

Hey folks, Spent my day replacing heater hoses, upper/lower radiator hoses and thermostat. Went to add coolant (with jeep off) and its leaking at the bottom of the thermostat housing. Ggrrrrr! I replaced thermostat gasket and tightened to 15lbs. What do you all think it is? Bad. gasket/housing? I was sure to clean off surface and razor blade all the previous gasket residue. I even put a small coat of RTV on the gasket. Maybe that is where I messed up. Please advise.
THanks, Matt

 

[J R]

Hey folks, Spent my day replacing heater hoses, upper/lower radiator hoses and thermostat. Went to add coolant (with jeep off) and its leaking at the bottom of the thermostat housing. Ggrrrrr! I replaced thermostat gasket and tightened to 15lbs. What do you all think it is? Bad. gasket/housing? I was sure to clean off surface and razor blade all the previous gasket residue. I even put a small coat of RTV on the gasket. Maybe that is where I messed up. Please advise.
THanks, Matt

I don’t use thermostat gaskets. Just RTV. Make sure everything is clean and dry. Never any issues.

 

[someguysjeep]

and i've never used RTV just a skim coat of indian head to keep the gasket stuck for fitting. never had an issue.

 

[MountaineerTom]

I used a gasket with no RTV at all this last time. In the past I’ve used a light skim of RTV on both sides. It was still a mess to clean up with the RTV.

 

[Rentmoney]

The thermostat may not be seated properly in the round indention that it goes in

 

[Wajeep]

I used a gasket with no RTV at all this last time. In the past I’ve used a light skim of RTV on both sides. It was still a mess to clean up with the RTV.

I am deflated. took off the thermostat housing and replaced it with a new one. It was looking pretty sad. Then I replaced the gasket again started filling up the coolant and it began leaking again. What gives!

 

[Wajeep]

I don’t use thermostat gaskets. Just RTV. Make sure everything is clean and dry. Never any issues.

do you use special water pump RTV or just the blue stuff?

 

[ColoJeep]

Make sure the T-stat stays in place as you put the housing to the block. And remember
Permatex High Tack is your friend........................

 

[J R]

do you use special water pump RTV or just the blue stuff?

https://www.amazon.com/dp/B0002UEN1U/?tag=wranglerorg-20

 

[Wajeep]

Make sure the T-stat stays in place as you put the housing to the block. And remember
Permatex High Tack is your friend........................

Should I add that stuff with a gasket? How much do I put on both sides of gasket or only one side. I have tried two gaskets and still leaking...

 

[ColoJeep]

Should I add that stuff with a gasket? How much do I put on both sides of gasket or only one side. I have tried two gaskets and still leaking...

A light coat to both sides of the gasket, make sure the t-stat housing isn't warp and is flat all around the sealing surface.

 

[Matt131]

I agree with comments above. If the 2 surfaces are clean and flat, theres no way it would leak unless the thermostat dropped down out of the recess during install and isn’t allowing the housing to seat properly.

 

[MountaineerTom]

Make sure there is no residue on the the block too. None. Take a razor blade if you need to a scrape any and all signs of past gaskets and RTV,

What thermostat are you using? I was going to use a Stant last time I changed mine. I was also going to drill a small hole at the 12 o'clock position to help air escape the block. I didn't pay attention to the t-stats at the time, but when I was test fitting I noticed the Stant had a taller bridge that the MOPAR and hit the housing when I tried to position the t-stat with the newly drilled hole at 12 o'clock. If I had noticed this before hand, I would have drilled in a different area. I ended up using a MOPAR t-stat.

Bridge hitting the housing, flange not resting on the housing

T-stat rotated, bridge not hitting the housing, flange resting on the housing.

 

[joe98tj]

and i've never used RTV just a skim coat of indian head to keep the gasket stuck for fitting. never had an issue.

X2 on just the gasket and some indian head

 

[Flivver250]

Like the wise men said above, clean up the surfaces, use a good gasket and a tiny bit of gasket tack. I tack the gasket to the housing side. I prefer the Fel-Pro 35630 gasket and the Super Stant 195° T-stat. Make sure the T-Stat is ressessed in the head. I always pop the belt loose so I do not have to compete with it when installing the lower bolt. That only takes one extra minute and it gives me a straight shot. I change 2-3 of these every Friday during our weekly wrenching meets and never a leak. I never use RTV.
That is just creating a future mess IMHO. https://www.amazon.com/gp/product/B00270U376/?tag=wranglerorg-20

 

[Flivver250]

BTW, I always pull off the T-Stat housing and put it on the wire wheel to remove all the smegma and corrosion. Often these housings are pitted and corroded, I replace them if they are real punky. My guess is you are letting the T-stat slip down between the housing and the mating surface. Want to make a big difference? Pop in a new fan clutch from Hayden whilst you are at it and flush the block with Thermocure.

 

[RaymondT]

If you haven't sorted it out, check out my old thread. I had to trim a few thou off the perimeter of the thermostat flange so it would completely fit into the recess, and I was using the Stant Superstat. It looked and felt like it was seated right, but it turned out to be just hanging up on the bottom edge where you couldn't see it. Two housings cracked. I use 320gr and a flat edge to take a little bit off all around the flange. 5 min job. Tolerances....

https://wranglertjforum.com/threads/thermostat-replacement.2078/