The ROM just says to use a new gasket when fitting a new stat, no mention of rtv or the like. When I removed the old stat it's clear the PO used a sealant, but no actual gasket. It didn't leak.

What's the current wisdom on using just a new gasket by itself or whether to add something like rtv or permatex thermostat gasket sealant?

 

A lot depends on access and the condition of the mating surfaces.
Poor = gasket plus RTV.
Good = dry paper or RTV alone.


Some years ago, I swapped the t'stat in my 79 IHC 304 V8. Very clumsy stacked iron assembly to house it. I gave up on aligning it with the paper gasket. Swabbed the surfaces with RTV. Slick, easier to match up, fixed, no issues.


The exhaust manifolds on my LT1 are 'sealed" sans gasket with hight temp sensor safe RTV. Much easier assembly, better match, no leaks!!!


SBC guys learned to use RTV on the ends of the valve chamber cover.
Aligning the neoprene was always iffy, RTV, positive seal.


Carl

 

I like Permatex #2 on thermo gaskets (and just about everything else, actually) but Carl is correct: if the surfaces are pristine you can get by easily with just the gasket only...or RTV only.


Heh heh, years and years ago I was in a bind (can't remember the situation exactly) and tried RTV-only on a thermostat housing. I had doubts that it would work...or would work for very long.

I was still leak-free *years* later when I sold the car!

Cheers
DD

 

You probably don't need a sealant in this case. Historically speaking, in the 80's most mechanics would have a bottle of indian head gasket shellac. That stuff would fill any small scratches and act as an adhesive so the gasket wouldn't move around during installation. I still use it when its called for.

As a serious home mechanic, I use RTV as little as possible. It's expensive, and makes for a sloppy looking repair as it oozes out and seems to get on everything. It's often used as a crutch, when no gasket is readily available, at hand or when no forethought was given to the project. That's fine, stuff happens, but it only take a few minutes with some gasket or cork paper and knife to simply make one yourself. In some cases where hard to find parts have been machined or fit poorly for some reason it's does the trick.

 

I always used to use a smear of Hylomar as often the mating surfaces weren't all that good.

 

I clean the mating surfaces, and use a thin smear of RTV between the gasket and item being bolted on. The surface facing the engine I always leave dry. Makes life a lot easier down the track when you pull things apart. Last time I did a thermostat the guy had two gaskets and RTV everywhere. Quite a mess and all because of some crappy warped chrome accessory piece. Standard item, standard gasket, a miracle! it all works :-)

Getting all kinds of answers, arent you? :-)

 

I use Permatex No.3, non hardening sealant. On almost everything, you can clean up overflow easily with IPA. Same you remove the gasket for next time, it just rubs off with IPA (isopropyl alcohol).

 

Wow, I seem to have touched off the greatest debate since Tastes Great vs. Less Filling.

When I took apart the housing, which didn't leak, there was no oring and a flat gasket. The factory gasket is a thin piece of metal with rubber-like coating.

I was asking because I wanted to have all the parts before I took anything apart, but that was not to be anyhow. The replacement gasket, that supposedly would get to my Pep Boys in one day still isn't there after 6 days. I ended up getting a sheet of gasket material and cutting out my own. Of course if I had known I would be waiting a week I could have ordered a real one from the east coast. Anyhow, wish me luck with the home made one.

My favorite sealer is called Gasko-cinch and I think it's still made, now by edelbrock. But hard to find. I have taken to using the one in a spray can because it's so easy.

Thanks for all the collective knowledge

-mB

 

Late 40's and early 50's. Exposure to wrenches. Amateur and pro mechanics used these:

1. Grease. Locate and secure a paper gasket in place for assembly.

2. Indian Head shellac. Locate and seal.

3. Red Permatex. Non harden. Seal and locate.

4. Black Permatex. .Hardens with age. Best in tough spots.

5. Gasket material or merely thin card board!! Made the gasket.

5. A pair of scissors, a sharp knife, a small hammer and tubi8ng with the end ground sharp. The latter to make clean holed for fasteners,.

Carl

 

Yes,
Great to use. Not "invasive" appearing when used.

I first used Hylomar when I worked in a restoration shop while working my way through college.