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Oil Leaks, Gaskets and Seals

May/June 1998

Seals are used to keep fluids in where they are needed and sometimes to keep contaminants (like dirt) out. Seals are used between parts that have relative motion. If there is not normally relative motion, then the part is a gasket of some sort. Sometimes the same or very similar material can be used as either a gasket or seal in our old Fords.

Seal technology has advanced a bit since 1932. Fluid leaks common then are not easily tolerated now. Today's lubricants are far superior to those of the 30s, allowing them to leak more than older lubricants, especially with the old seals.

So, how can we keep oil in the crankcase where it belongs?

We can minimize leaks with proper installation techniques. The "rope" oil pan to engine block seals, the front being the same as the Model A, can do a fair job if installed correctly. Once made of asbestos with a rubber binder and sometimes a graphite fiber or rubber cord or core, the ones of current manufacture are acrylic and fiberglass yarns with a rubber binder. They feel "limp" compared to the older asbestos fiber seals.

There are a couple of "full circle" lip seals now being marketed for the front of the flathead V-8s. They are installed with the pan and front timing cover off.

Slide the seals on to the crankshaft seal surface, or the crankshaft front pulley surface, with light unfilled grease or heavy engine oil on the lip and the seal surface. Insure that the primary lip is pointed towards the INSIDE of the crankcase. Then install the pan and front cover with the appropriate gaskets. The pan rail gaskets will have to be trimmed to clear these new type seals.

At the rear of the block, the old style "rope" seal is still the best we have, as far as I know. Many have worked on a two-piece rubber lip rear main seal, but I know of none available now.

Here's the best recipe I have found for installing the rope seals:

Soak the seal pieces in engine oil for to 4 hours. Before fitting the seal pieces into their cavities, do a dry fit on the pan, front cover, and or rear main cap and upper seal retainer. Remove burrs at the parting lines, if needed.

Before installing the pan, check for proper cam timing, and that the cam bolt lock plate tabs are securing the cam bolts properly. Check the security and safetying of the oil pump. (You did prime it with clean oil, right?) Check that the screen is not against the bottom of the oil pan but is withing 3/8 to 5/8 inch from it.

Check the pan for flatness. Do any "body & fender" work required to make it all fit right. Check the pan side gaskets to make sure they are all the correct ones and haven't shrunk in storage. If they have, soak in warm water to expand them.

When you are satisfied it will all fit together correctly, then install the oil soaked seal pieces. Hold the retainer(s) securely so that you can put some force into forming the seal into its cavity.

Center the seal and push the center into the cavity. Then use a large fluted screwdriver handle and turn it in the same direction you are moving and "iron" the seal into place. If the ends come out uneven, pull it out, shift its position a bit, and do it again until it is right.

Almost all of the flathead rope seals are sold cut to length. After soaking in engine oil and being properly "ironed" into place, they will be proud +/- 1/8 inch on each end. They should NOT be trimmed, as they will compress properly with the design load on the pulley or crankshaft seal surface if not trimmed. Oil will squeeze out -- don't worry about that until you get the seals correctly in their cavities.

Place the pan gaskets so that the holes line up. I use a thin coat of silicone sealant on each side of the gasket. Put unfilled grease on the seal surfaces and bolt it all together. After the oil quits squeezing out of the seals, you can clean it up and go to the next item(s) on your list.

If you have a crankshaft that just can't hold and seal, check the seal surfaces for runout and finish. The runout should be less than .001 inch and the surface should be smooth with no mechanical damage.

On the 1932-48, if you have trouble with the gasket that goes between the rear cap and the pan, you can soak it in warm water, then dry it in a #303 or soup can. If dried in this curvature it will want to stay in place instead of "popping" out each time you let go of it to reach for the oil pan.

My question to you: why do some labyrinth, double slinger rear seals leak and some not leak (much)?

- Red.

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