RTV / silicone question

I bought a couple different RTV / Permatex products, but I want to get some opinions if they can be used in all areas of the tractor rebuild.

Hi Tack Permatex - this is a brush on type sealant - do people use that for just paper gaskets or is it ok for cork too?

Ultra Grey RTV - it was advised to use this on cork, but I'm wonder if the high tack will be just fine that I mentioned above

I also need something to do the bolts that go into the inside of the threaded holes. There are front cover bolts that will enter the water jackets as well as into the trans/rear axle, like where the brace that holds the step. It looks like over the years, the threaded studs have just been replaced with bolts in places. What is the right RTV for sealing threads? I'm thinking maybe the Ultra Grey will work but I saw some other blue RTV saying it's for threaded application.

Thanks in advance, the options of RTV/sealant have gone wild. Can I use one for everything by chance?

thanks, moday

I personally don't use anything on cork, makes it too slippery and risk squishing the gasket out of position. Use a little 3M gasket adhesive if you wanna "glue" the gaskets to one side.

Most gaskets I don't use any sealer. But if needed I use Permatex Aviation sealer (80017). Places I use this is: corroded surfaces, water pumps and thermostats, head gaskets, unless they specify No Sealer. I don't use high tack, way to sticky / stringy. Makes a mess.

RTV only gets used sparingly when there is no paper gasket, or where a paper gasket won't seal. 9N,2N, 8N governors come to mind. Modern tractors that don't use gaskets, etc. Here I like Ultra Gray for it's oil resistance qualities. Remember, almost all RTV you put on gets squeezed out. Apply sparingly and correctly. Most call for sparingly, then finger tight for an hour or so, then button down.

I use Permatex Avaition sealer, in a little plastic bottle with a dabber brush...probably the same type thing as with the product you mentioned. or PT #3. On cork automatic transmission pan gasket replacements I found that painting the pan side only makes the best seal....besides holding the gasket in place when reinstalling....the other side needs to squirm a little so I leave it dry....painting both sides leaked so I quit it. I'd apply that process to any cork gasket...glue one side only.

On paper and synthetic products that don't squirm, I paint both sides.....I even paint both sides of metallic head gaskets but I use Copper Coat for that task as that is the reason for its being...never have to go back and tweak valves and disturb my nice clean freshly painted engine.....never had a call back.

I try to stay away from magic sealers and let the gasket do the job it's intended to do, most quality gaskets you buy today can do the job alone. If I need to hold a gasket in place I will use grease on cork or a dab of yellow weatherstrip adhesive to hold it. If parts are pitted or questionable I might add a very light coat of RTV. There are some places where you can use it to eliminate a gasket or there is no gasket available, like a differential cover. The majority of RTV used goes to clog oil pump screens and radiators as it squishes out then breaks off internally. For sealing threads you can use non hardening Permatex in a tube or thread sealer.

Most gaskets don't need any sort of sealer. If I need to hold a gasket in position for assembly, I'll use Hi-Tack or maybe just a bit of grease.

If I can't get a gasket or need to seal bolt threads, then the RTV sealant shine. Of if there's damage to a sealing surface such that a gasket alone won't work.

the old permatex no 2 or now aviation sealer in the big big bottle. Try to paint one side of gasket only unless water pump or thermostat..

Where no gasket and have to make one, then usually a very very thin coat of rtv... let it sit a minute with the cover on, but not fully tight... then crank it down before it fully hardens, as I dont want a thick layer, only a thin layer substitution for the missing gasket is needed in most all cases...


a valve cover may by different as they are usually warped.. so I reflatten the cover between holes, using a hammer and piece of stock..... and then use a thicker layer, preset the cover,, and let it harden before final tightning..... This is an exception though.

I wouldn't use RTV on cork. It'll make the gasket slip out. For threaded holes, I use PTFE from a hardware store.

When I have gone back after a few years where we used silicone on threads where there was water or antifreeze on cast iron we found that the rust had crept along between the Silicone and the cast iron. Not pretty.

Its trial and error. : ( Unlike modern engines these old ones were built to leak... Dang tin covers unless new you will never beat them straight again are achieve the original clamping force. The worn machined sealing surface is corroded to where a plain gasket may leak.

Each application a sealer has its rightful use some figure it out some don't. Its trial and error.

Paper is very forgiving cork is in its own world. Paper and most sealers get along well, cork does not get along with itself mush less any kind of sealer.

When possible I find it best to just eliminate the cork... Ha Ha that comes with its own issues. I have removed valve covers and such (tin covers) that were sealed with the right stuff even a intake are two I thought I was going to destroy the parts that were nailed so good. I will say if there were no reason to go back into it are the RTV was applied correctly they would have never leaked. There are places RTV over cork RTV is king... It still comes back to trial and error.

Engine building One winner RTV verses cork if its a thin cork gasket the cork gets tossed. Its still trial and error. Valve lifter covers with a thick cork gasket it boils down to even clamping force that I doubt you will ever make new again sealer are no sealer.