What do you put on gaskets?

[TiggerToo]

When you assemble engine bits (e.g. carburettor on a small outboard), do you smear anything on the gaskets (e.g. grease? oil? which?) before tightening them up? Or do you just put them on "dry"?

 

[Playtime]

I use grease. Makes them slightly 'softer' to bed down and easier to dis-assemble years later. It also keeps them in place while fitting the mating piece.

 

[wotayottie]

Nothing

 

[anoccasionalyachtsman]

Blue Hylomar on paper/card gaskets, nothing on the more modern types unless the book says otherwise.

 

[PaulRainbow]

I use grease. Makes them slightly 'softer' to bed down and easier to dis-assemble years later. It also keeps them in place while fitting the mating piece.

This is the correct and time honoured way to assemble with paper gaskets and head gaskets. For all the reasons you give.

Using any form of sealing goo is incorrect, except in special circumstances. The gasket is there to seal the joint, there is no need to add silicone, hylomar or hermetite etc.

 

[ghostlymoron]

I also just use a thin smear of grease. Anything else is unnecessary.

 

[theoldsalt]

I also just use a thin smear of grease. Anything else is unnecessary.

Agreed.

However it is important that the mating faces are flat without burrs. Often the necessity to add sealant arised from not ensuring a good and clean fit.

 

[Poignard]

Dry

 

[oldharry]

Sealant on carburettor gaskets is a sure fire recipe for trouble. It only takes a tiny bit to block those fine jets. However carefully you apply it, there is bound to be some surplus squeezed out on the inside which you cannot wipe off. Red hermetite in petrol is a particulalrly bad mix and almost guaranteed to cause a blockage.

 

[lw395]

It depends on the application, and the gasket material.
Sometimes, gluing the gasket to one surface and greasing the other surface works very well.
An example might be an impeller water pump. This will give you a good chance of re-using the gasket.
Generally, RTFM.
If Ducati tell me to use an obscure goo, I'll do that rather than find my normal practice doesn't work as well and have to do lots of work to start again.

An outboard carb, I would not use any sealant (unless desperate having failed several times without), as even a small amount of it breaking free and getting in a jet is going to be annoying at best. A good quality carb gasket will probably work dry. A smear of grease generally won't hurt and will hold the paper in place during assembly.
Sometimes cheap pattern gaskets are very thin compared to original, either make your own using the right thickness gasket material or add the thinnest smear of sealant.
Sometimes sealant will help with damaged surfaces.

 

[superheat6k]

An old, well compressed gasket can be refreshed as an emergency measure with a smear of Loctite 577, as can flattened O rings, but it is preferential IMHO to replace both whenever necessary. I prefer an oil smear on a new gasket, and this is our routine procedure on refrigeration compressor gaskets.

 

[<152587>]

This is the correct and time honoured way to assemble with paper gaskets and head gaskets. For all the reasons you give.

Using any form of sealing goo is incorrect, except in special circumstances. The gasket is there to seal the joint, there is no need to add silicone, hylomar or hermetite etc.

Grease on cylinder head gaskets, really???

 

[PaulRainbow]

Grease on cylinder head gaskets, really???

Yes, really.

Why, what harm do you think a thin film of grease will do to a traditional head gasket ?

If it's a coated gasket, where fitting instructions stipulate it goes on "dry" then that's different.