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Solving Sump Plate Oil Leaks

September 27, 2010 | Troubleshooting & Repair

Text by Rainer Cooney, Ken Daugherty, Alan Klingen, Ron LaDow

[Editor: After 50 years or more, 356 sump plates often leak. Here is a range of solutions to the problem from some of the veterans on 356Talk, as posted in November, 2008.]

Alan Klingen: Over the years the plate develops waves on the sealing surface from the nuts pulling it down. When the plate is off I lay it on a flat steel surface, such as an anvil, with the inside surface up and hit the stud holes to flatten them back down. You should also check the center copper rivet to see if has become loose. If you need to use a sealant use a non-drying one that be cleaned off at the next sump service.

Ken Daugherty: We 'flatten' sump plates by turning them upside down of an anvil, placing the ball end of a medium size ball peen hammer in the stud hole and carefully smacking the hammer with another hammer. This reforms the dimple caused by repeated tightening over the years. Caution, do wear safety glasses in case the a piece of one of the hammers chips off.

Ron LaDow: [Regarding using plumbers teflon tape to wrap the sump plate studs] That tape has a bad tendency to shed 'threads'; I wouldn't use it anywhere near the oil sump. If you're getting leakage around the studs, take 'em out, clean the studs and the female threads and replace them with some blue Loctite.

Rainer Cooney: Loctite, Permetex,Wurth, etc. anerobic case sealant on the gaskets and acorn nuts with 6mm copper sealing washers will prevent the traditional 10 oil drips from each stud.

[Editor: sump plates become deformed by overtightening the nuts. Here's how Harry Pellow advises you attach the plate:]

Harry Pellow: The Sump Plate Studs use a flat 6mm washer, then a wavy 6mm washer then the 6mm nut. Tighten the nuts from the middle out, alternating from side to side, and REPEAT ABOUT 5 TIMES! But do NOT overtorque them (7.5 foot pounds is plenty)! That's the only way to stop sump leaks. If the Sump Plate holes are deformed upwards from overtightening, use a Ball Peen Hammer to redress them until they're flat.


2 Comments

Profile missing thumb
John Holmberg
December 21, 2010 at 10:38 PM
Use an after market sump plate machined from an alumnium billet. They are very rigid and do not leak. They give a little more cooling and look neat too.
Profile missing thumb
John Holmberg
December 21, 2010 at 10:38 PM
Use an after market sump plate machined from an alumnium billet. They are very rigid and do not leak. They give a little more cooling and look neat too.