Cork Gaskets vs. Silicone

[Dan LeBlanc]

Hi All

I'm about to pull the engine in my Fleetwood to clean it up and regasket it (leaks oil like a basket - but hey, she's almost 50!).  I did the engine in my 62 with a full gasket set, got the valve covers to stop leaking but not so much with the oil and transmission pans.  This time I'm thinking of using silicone (very carefully) instead of gaskets.  I've used silicone in the past for the water pump on the 62 and had great results (followed the directions on the package perfectly - applied silicone as directed, installed finger tight, waited 24 hours to cure, and torqued to proper specifications).  I'm thinking that installing finger tight was to allow the gasket to take shape to the surface, then curing was to avoid all the silicone from oozing out when being tightened.  After two years of lots of driving it never leaked.

I know I've read somewhere that a common saying about these old Cadillacs is that if they're not leaking, they're out of oil.  Just wondering if a modern solution could be applied to an old problem and if anyone has success stories to share.

[mgrab]

Dan,
You might want to be concerned as far as your transmission is concerned.  An old school mechanic once warned me of using silicone on a transmission pan.....if it oozes a bit into the pan it could become free and possibly clog the ever so small passageways in your transmission.  About a year ago I flushed the transmission in a Mitsubishi Diamante I have.  I had this done a few years ago with a mechanic I go to locally when I'm lazy.  I bought the gasket.  When I dropped the pan I was shocked to see silicone...it didn't leak but when I removed the pan......what a task it was cleaning the mating surface.  I cursed the guy for the whole two hours of scrapping every single particle off so it didn't leak or get sucked into my transmission.  So I guess it can work.....but I wouldn't do it..
Mike

[kittykatjaz]

Hi Dan,

Don't use silicone on the transmission, it is evil and asking for trouble with your hydraulics. The best gasket sealer that I have used is Loctite Master Gasket, just a light smear on each side of the gasket and that is it. Though be meticulously clean with the surfaces and prepare with a solvent like the spray can brake clean on a rag or similar. The master gasket has the added bonus it does not set unless compressed so a tube will last for years.

Jaz

[The Tassie Devil(le)]

I know I've read somewhere that a common saying about these old Cadillacs is that if they're not leaking, they're out of oil. 

I thought that saying was referring to Jaguars.

Bruce.

[35-709]

"I know I've read somewhere that a common saying about these old Cadillacs is that if they're not leaking, they're out of oil."

I first heard it in relation to BSA & Triumph motorcycles, then radial aircraft engines, then Harleys.   

I have used silicone WITH the regular gaskets, just use a very thin "skim" coat on each side of the gasket.  I agree that using silicone only to make a gasket is asking for trouble.  If you ask an engine rebuilder acquaintance of mine about using silicone you will get a long, expletive laced response about all of the problems he has seen it cause.
Geoff N.

[Roger H]

One thing to check when ever replacing gaskets on sheet metal parts (oil pan, valve covers etc.)
Make sure the bolt hole area has not been dented inward due to over torquing or old age,  look at the part and make sure it is flat on the gasket side,  if not,  straighten it with a ball peen hammer and a backing device of some sort.

[Dan LeBlanc]

Good tips all.  I didn't know gaskets and silicone could work together. 

May be time to get out the body hammer and dolly to straighten the transmission and oil pans.