Leaky thermostat housing

[Larryjb]

All my searching has revealed this is a very common problem, with varying solutions with varying success rates. I'm kind of surprised that there is no technical article here regarding this.

I have removed and replaced thermostat housings on 7 or 8 cars that I have owned over the years. The OEM gaskets always worked fine with no issues. This is the first time I have had an issue with new parts. The water pump is not OEM, and I don't know when it was replaced. I have a new one, but because I couldn't find my clutch fan tool I decided to leave it for now and just replace the thermostat housing. I did wipe the area clean and lubricated the new thermostat gasket with fresh coolant. Normally, this has always worked and I've never had a leak. This 5.3L is a problem. I have heard that some use RTV, some use special thermostat sealant, some don't use any, but just make sure the gasket sealing surface is clean.

Can some one post a method that is reliable and will always work? I don't want to dig into this more than necessary, considering the amount of coolant I have to dump just to change a thermostat.

 

[brasil]

can you buy REINZOSIL from Victor Reinz in Canada ? If yes.. this is the right stuff for ALL Gasket Problems... this stuff is amazing It also is perfect for places to seal, where gasoline is in play. Any RTV will not work with Gasoline /fuel

On the other side...did you check the Thermostat housing for cracks ? Perhaps the former owner was "MR MUSCLE" ?? Wouldn´t be the first time that POWER kills a part

Greetings from Germany
Juergen

 

[mizzouguy]

I've done the thermostat on a few 5.3's, the older style that have the separate thermostat and housing. I've always just used a new thermostat by murray that comes with the gasket (45687) No issues. I know some brands have issues with interchanging the gaskets for the thermostats and housings that come as one piece. The other style that come thermostat/gasket as one piece use an o-ring to seal instead of a wrap-around gasket on the thermostat itself.

 

[sumo]

I use permatex hi tack. Works great. Never had any leaks

 

[Larryjb]

Thanks for the replies so far.

Juergen, it is a new AC Delco housing and thermostat. It could be cracked, but unlikely.

Shane, mine is the second style shown, which I guess is the newer style. Frankly the included gasket looks like it wouldn't take much to leak. And it is.

Ian, I'll look into the Permatex stuff.