j2b4o

95 ls400.
bought a new therm cause the car overheated (like 75%)than shot down than overheated than shot down than stayed high and I turned her off. changed thermostat with rubber gasket and used black rvt to seal the housing. runs fine than after idling for like 5min it starts to **** water vapor out the therm housing and the heat climbs. Ive redone it twice and am sick of doing it so if there is a secret or a trick Id love to hear it. It is leaking out the underside both times. this isnt even my car Im borrowing it and Id like to get her buttoned up tomorrow.

thanks!

hobojoe

Sure you are using the right torque specs? I'd have changed a few thermostats before though the gasket I replaced them with wasn't rubber, never had any problems using the right specs.

PureDrifter

iTrader: (10)

stop using RTV and go buy an O-ring-type gasket like you're supposed to

LiCelsior

iTrader: (32)

housing is prob cracked from what u describing.

Och

iTrader: (3)

I had the same problem. I bought an OEM thermostat, but didn't realize it came without gasket. I was too lazy to go to the dealership and bought a gasket from a local autozone, and it would leak just like you're describing. I got an OEM gasket and leak stopped - the OEM gasket was substantially thicker than aftermarket one from autozone.

Just get OEM gasket and thermostat, and you shouldn't need to use RTV silicone.

hypervish

Try using a gasket, and be sure to dry surface before putting the gasket on. If need be use a tiny bit of RTV sealant but not much, try not to use it though. As others have suggested, if it continues to leak your thermostat housing may be cracked. Try inspecting it closely for any pin holes, or a crack forming.

The key for the thermostat to seal properly is for the surface to be dry, like I mentioned earlier dry the housing before putting the seal on. This is a common mistake, many people come to my uncle's shop with a leaking thermostat housing. We ask them if they dried the surface with napkins and rags before putting the gasket in place and torquing the bolt, the answer is always NO, or it's how did you know. lol

j2b4o

Ok so like I said in the first post I REPLACED THE RUBBER GASKET along with the thermostat.
The ls doesn't call for a flat gasket like most other cars hense why the rvt to seal where the housing detaches. This is how it was previously and I scraped it off and dried it. I am aware of typical procedures for thermostat replacement. This is not typical and there is no crack in the housing. Will a flat gasket work from another car? Should I really go all the way to the dealer for a 2$ rubber gasket when I already have one in there?

PureDrifter

iTrader: (10)

if you listened you would have the answer to both questions.

the aftermarket gaskets generally do NOT FIT PROPERLY. buy the $2 oem gasket and problem solved.

when assembled properly you don't need RTV or a paper gasket. when improperly installed these things will create a gap not letting the rubber o-ring not seal properly.

LS400Mike

I have replaced the thermostat in my 90 ls 400 and used gasket maker with good results. Its been 4 years with no leaks. I didn't have to do anything special to get it to work. I used a universal 180 degree thermostat and regular blue gasket maker. Didn't use a torque wrench either. I would be inclined to believe that someone either bent or cracked the original thermostat housing torquing it too hard or with some foreign object in the way. If you know the procedure for changing the thermostat on any car you have one up on me when I did the job. It was my first thermostat. Thats why I want to believe there is a part damaged on yours.

j2b4o

found out I already had an OEM therm and gasket so no need for a trip to the dealer. disassembled & scraped off all gasket sealer, re-assembled. put water in the plug above the therm and everything is fine now.