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'55 Hydramatic Pan Leak

Started by njones68, March 13, 2013, 01:16:51 AM

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njones68

I have a continuing problem with the pan leaking on my '55. Have done all the usual fixes, taking off the pan, straightening the flange on a flat surface, correct torque on the pan bolts, aviation gasket seal on new gaskets, still leaks. ( Don't like silicon sealers, too many problems with bits of silicone getting into the "works " )

Seems to me the problem is the slight dimpling that occurs when the bolts are tightened allowing the gasket to seep. Years ago I recall early Chevies (30's) used a winged washer under the pan bolts to spread the stress, these washers had a tab on either side of the hole which prevented the 'dimpling".

Anyone have any ideas who still supplies these, I think it would fix this problem experienced by most hydramatics.

Nigel Jones, BC, Canada

Caddy Wizard

#1
It sounds like the bolt holes are dished.  If the holes are dished (as from ovetightening), when you tighten the bolts the gasket will get squeezed really tight right at the bolt hole and not so much inbetween the bolts.  If that is the situation,  it will never seal.

To fix that, take a length of 1x2 lumber (actually about 3/4x1.5) and stand it on end.  Use the end of the block as an anvil and use a small machinist's hammer or a small body hammer and hammer the bolt holes flat again. The end of the lumber will fit neatly into the shallow bolt channel formed in the pan.  Then clean it up with a bit of sanding, moving the sand paper lenghwise along the periphery of the pan, not across it.  Once done, be sure to stick to the torque spec.  Now, I was a practicing mechanic for 10 years and I often didn't use a torque wrench on every bolt on every job -- speed was king and for most bolts it doesn't make that much difference.  But these pan bolts really need to be torqued to just the right spec.  If overtightened, they will leak.  I like to torque them to spec and them re-check them in a few days or a few hundred miles.

You should be able to get the pan gasket to seal perfectly -- no drips at all.  One more thing I like to do is to use a brass drain plug gasket that has an inner rubber seal to grip the threads of the drain bolt.  I think the size you need is sold in the parts store as a 9/16".  I find that these seal much better than a plain steel, brass or fiber gasket.  The only downside to them is that they really can't be reused -- one or two uses only and then the rubber bit is trashed and you have to throw them out and use a new one.

Good luck.


Art Gardner


1955 S60 Fleetwood sedan (now under resto -- has been in paint shop since June 2022!)
1955 S62 Coupe (future show car? 2/3 done)
1958 Eldo Seville (2/3 done)


wrench

#3
I use this stuff on a lot of gaskets, might be worth a try if the flange is flat and clean/dry and the case is clean/dry with no oil residue (use brake cleaner). Spray it on BOTH sides of the gasket. (a new gasket)

http://www.permatex.com/products/product-categories/gasketing/gasket-sealants/permatex-high-tack-spray-a-gasket-sealant-detail
1951 Series 62 Sedan
1969 Eldorado
1970 Eldorado (Triple Black w/power roof)
1958 Apache 3/4 ton 4x4
2005 F250
2014 FLHP
2014 SRX