RTV vs. gasket sealant

[das_peikko]

Originally Posted By: Lubener
Personally, I would never use RTV on the surface of any gasket, only the joints.


Correct. RTV is to be used as either a replacement for a gasket, or at the four corners of an intake manifold.

 

[andyd]

Originally Posted By: das_peikko
Originally Posted By: Lubener
Personally, I would never use RTV on the surface of any gasket, only the joints.


Correct. RTV is to be used as either a replacement for a gasket, or at the four corners of an intake manifold.
Black RTV on the edges of a rope sealed rear main.or where the timing cover meets the pan,etc. Aviation Forma-Gasket is more gas resistant than RTV. I think it plays better with coolant systems than RTV. It is the bee's knees for pitted aluminum hose nipples and acts as a lube to ease hose installs and removals. #2 is like Hylomar. It skins over in 15 minutes and never hardens. RTV takes an hour to work and 24 hrs for a full cure.

 

[nthach]

Gasket sealant(Permatex #1-3, high-tack) are chemically different than RTV. RTV is silcone that cures on exposure to moisture via a catalyst. Automotive-spec RTV doesn’t release acetic acid/methanol upon curing. Gasket sealers use synthetic resins or gum rosin and a small bit of latex.

I use high-tack to hold rubber or paper gaskets in place, and never goop RTV on any gasket or it won’t seal as intended.

 

[Trav]

Originally Posted By: das_peikko
Originally Posted By: Reddy45
If Permatex Form-a-Gasket Sealant #2 is not RTV, then what is it?


Whatever it is, it can only be broken down with hydraulic brake fluid. It's very effective in treating cork and paper gaskets making them oil and waterproof. Gasoline takes a long time to break it down.


Today I use Hylomar M, Anaerobic sealers and high tack, its very seldom I use RTV or #2, when its usually Honda bond for oil pans.
Shellac is still preferred from uncoated paper gaskets (seldom used today) so a bottle of Indian head is still around but sees less use all the time.

 

[nthach]

For RTV, I use Toyota's FIPG on things that call for it. Permatex Ultra Grey in a pinch. To keep gaskets in place or to bond them to a flange, high-tack. Fel-Pro uses coated/treated paper for their fiber gaskets but I like to coat the non-printed side with a coat of high-tack to keep it there.

 

[SZR48207]

So unless you are using a VERY old school paper gasket (that would weep fluid), most people are using "Gasket Sealant" to merely stick the gasket to the surface for easy assembly?

 

[eljefino]

I'll use RTV along with a supplied gasket if something doesn't seem right, eg there's pitting/ corrosion. Part of this idea being it takes up a little of that third dimension eg acts like a filler.

 

[willbur]

Originally Posted By: andyd
Originally Posted By: das_peikko
Originally Posted By: Lubener
Personally, I would never use RTV on the surface of any gasket, only the joints.


Correct. RTV is to be used as either a replacement for a gasket, or at the four corners of an intake manifold.
Black RTV on the edges of a rope sealed rear main.or where the timing cover meets the pan,etc. Aviation Forma-Gasket is more gas resistant than RTV. I think it plays better with coolant systems than RTV. It is the bee's knees for pitted aluminum hose nipples and acts as a lube to ease hose installs and removals. #2 is like Hylomar. It skins over in 15 minutes and never hardens. RTV takes an hour to work and 24 hrs for a full cure.


Old time techs told me to cover the rtv sealed parts with a damp rag to hasten full cure. According to them, rtv cures quicker in the presence of humidity. Never tried it. 24 hrs for full cure is just too long to wait.