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Here's are some basic questions for you....


Country flag
So I was about to install a new thermostat and new elbow water outlet. Somehow this is the first time I've actually had to do this on any of the cars, and it got me wondering about;

1) what sort of sealant I should use around the water pump and elbow.



2) what actually holds the thermostat in place? if it a mechanical fit where the elbow presses down on it? Any sealant on the edge of the thermostat itself?


Staff member
Country flag
not sure about the #1 but, no sealant on the thermostat itself - it just sits there.


Jedi Knight
The themostate just lays in place. "MAKE SURE it is in correct way. there are only two ways. the correct way and the backwards way. do not install any type of gasket sealant etc...

Clean the block and housing with a dull putty knife until all is clean, I normally will rub housing on a flat piece of 200 sandpaper to check for trueness. and really put a good flat edge on housing. with the studs in the block you will not be able to do that side but you can use a pot scrubber to clean well.

The sealant shown can be used with a gasket or with out a gasket, I perferr the gasket

Gasket installation: spread the RTV thickly on your clean finger and butter the block and one one side of gasket evenly, lay gasket in place on the block so the gasket side with rtv is facing up. Then butter the housing with rtv and lay on top of gasket. do not apply pressure or bolts. wait 3-5 minutes then snug the housing bolts down evenly. to not overtighten and warp the housing or shear off studs.

No gasket installation: apply a thick bead of RTV on to block where housing mounts. you want a "solid bead" 1/4" high completly around the opening, spread with finger if needed for uniformity. wait atleast 5 mins until rtv has skinned. then mount the housing and secure as above.

Waterpump installation will be the same. Normally water leaks in these areas are no prevalent


Luke Skywalker
You have to love "marketing"
RTV (Room Temperature Vulcanizing) Is all the same as per the GE Silicone sales rep who told me this back in the 80s.
#1, it will not stick to oil or oily surfaces including oily wood like teak, cedar, redwood.
#2 It is all the same except for the packaging, what is inside might be a different color but RTV is RTV and it all vulcanizes at ROOM temperature.
So if you want a lot of RTV, buy it in the caulk tube for your bathtub.
You can pay the same price for 1/2 an ounce as you would for 10 ounces but it would be marked High Performance Automotive gasket goop.
#3 We do add metal (aluminum powder) to roof RTV sealants just so it matches metal roof chimneys.
Why do we do this? he asked. "Marketing", who in their right mind would use window or tub caulk on their high performance car engine!
So I have been using window or tub caulk for 25 years, it works fine.
I normally only use it on the pan and valve cover because they do come off and can be replaced with the old gasket.
For most other gaskets, I just use a smear of grease to hold it in place during assembly.
Do my Sprites leak any oil? Well sure they do but not from any gaskets.
I do not know if GE has changed anything in RTV sealants over the past 3 decades but why would you pay $4 for .05 oz when you can get 10 ozs for the same $$?
Oh yeah, marketing :wink:


Use RTV very spareingly. I owned a car that would not stay cool in hot weather so took the rad to a rad shop for a boil out. He removed the tanks and found 1/4 of the tubes plugged with little worms of RTV from previous owners. He was adamant about not using ANY RTV for ANY engine work.


Great Pumpkin
Country flag
I like RTV, even for engines. You just need to pay attention. Never more than a *thin* film on gaskets. Gooping it on mating surfaces is baad juju.
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