How to fix leaky seals and jumpy gauges

Jumpy fuel gauges are most often caused by bad grounds or loose connections.

Hagerty member Dick Jacobs writes: I have an all-original 1933 Buick Model 67. Over the past several months, oil leakage from the rear main bearing has increased to a point where I am afraid to take the car out of town. The shop manual I have refers to a cork seal on the crankshaft, but it doesn’t say anything about replacing it. I live in a small California community, and there are limited resources available. How can I slow the leak?

I have three pieces of bad news for you. First, if the oil leak is past the minor annoyance stage, I don’t think there’s any way around pulling the transmission, dropping the oil pan to verify that the rear main seal is the source of the leak, and replacing it.

Second, Buick straight-eight engines from 1934 share a lot of parts with those up through 1953, but the 272.6-cubic-inch engine in your ’33 is of an older generation, and parts are harder to come by. Egge, in Santa Fe Springs, California (Egge.com or 800-866-3443), is the only shop I could find that sells the entire gasket set for that engine, but it’s expensive (part RS830, $776). Both Jim at Egge and Glenn at OldBuickParts.com advise that the cork rear main seal can be replaced with a later, easier-to-find rope-style seal.

The third bit of bad news is that both the cork and the rope-style main seals are two-piece, and it’s challenging to change the upper portion without dropping the crankshaft.

The good news? High Desert Auto Care (760-961-4476) isn’t far from you and says it’s familiar with how to remove the crankshaft end cap and fish the upper part of the seal in and out. You might want to give High Desert a call.

Hagerty member Tom Marrin writes: I have a 1954 Chevy Bel Air that had a body-off restoration several years ago. In the process, the gas tank and the sending unit were replaced. The gas gauge then read empty even with a full tank of gas, so I took the car to a mechanic, and he found that the wire from the tank to the gauge was pinched. He repaired the wire, but now the needle on the gauge jumps back and forth when I’m driving the car. Could the sending unit be installed in the wrong position? Further, what keeps the needle from jumping around when you go around a corner?

It’s possible the sender is rotated in its mounting flange, but that shouldn’t make the gauge jumpy. Since most fuel senders are simply level sensors, in theory they can be thrown off by changes in the fuel level caused by starting, stopping, or turning, but most mitigate this effect by having the float located near the center of the tank or by enclosing the float inside a cylinder with a small hole in it so the gas can’t run into or out of the cylinder quickly.

Bad grounds or loose connections are generally the cause of jumpy gauges. Verify that the tank and the gauge have good ground connections to the body of the car. Next, check that the gauge connections for “power” and “sender” are both tight. If you disconnect the “sender” wire, the gauge should go to full. If it still jumps around with the sender wire disconnected, the problem is with the gauge. If you then reconnect the sender wire and ground the other end, the gauge should drop to zero. If it doesn’t, there’s a break in the wire. It’s possible the wire wasn’t repaired properly, so try running a new wire from the sender to the gauge to see if the problem goes away.

[This article originally ran in Hagerty magazine, the exclusive publication of the Hagerty Drivers Club. For the full, in-the-flesh experience of our world-class magazine—as well other great benefits like roadside assistance and automotive discounts—join HDC today.]