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Sealant - Gas Tank Sending Unit

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healeygal

Jedi Warrior
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Hello all,

What is the recommended sealant, if any, for the gas tank sending unit gasket? This is about the third time gas has started seeping, with a little pool forming (about 1/2 teaspoon) - twice in the past the blue stuff didn't work, and with a recently installed new gasket, using nothing doesn't seem to be working either. The problem happens when filling the tank up to the filler neck, which I don't ususally do, but on the trip home from Palo Alto, wanted to get as many miles on a tank as possible. Is there a solution other than not filling the tank up all the way?

Sharon
BN1
 
I don't know Healey specific answers to your question however I do work with gauges and sending units fairly often.

First, if by "the blue stuff" you mean RTV in a tube... NEVER use RTV on anything exposed to gasoline. Gas is one of the few things that will attack RTV.

If the gasket is cork (as used on a lot of the early Smiths sending units) I believe the traditional approach was to soak cork gaskets in 30W motor oil overnight before installation. I however don't like doing that.

When I install either bolt-on or bayonet mount sending units on tanks I apply a thin film of Permatex Aviation Form-A-Gasket to the gasket regardless of whether it's cork or rubber. You can also use the thicker Permatex-2B sealant in a tube. Both of these are immune to gas exposure, stay soft so you can remove the parts later, and won't attack the rubber.

In an ideal world the sealer won't be necessary but a little sealer will plug any pin holes, surface roughness, or gasket voids to prevent leaks. Again, don't use RTV on anything exposed to gasoline.
 
I'll second Doug's remarks--I made the mistake last year of using Hylomar in trying to reset an old tank gasket. It's wonderful stuff but too squishy for this application and lots of what I applied wound up in my fuel tank (and passed through to an inline fuel filter totally unphased by being immersed in gasoline)plus the gasket still leaked. Ultimately I got a new gasket and set it in permatex with no leaking whatsoever.
 
By far and away the best fuel gasket treatment/sealant I've used is a product called FULELUBE (there is a sister product called SEALUBE specifically for threads and the like). It seems to be an aviation product as aviation catalogs have been my only source over the years. It is designed for o rings and gaskets whether paper or cork or rubber. It is a thick sticky consistancy ( I often use it to stick a nut or washer on the end of my finger in hard to reach places) Dries a bit but does not really harden. It is absolutely resistant to gasoline or jet fuel. Great product. If there is an aircraft shop near you they might give you a bit in a baggie as it is all you will need. A can would last one person a lifetime (comes in pints).

Jon
 
Thanks Doug, Michael and Jon! Found a tube of 2B in the garage, plus have a new cork gasket bought from Moss on the way home from up north (smallest order I've ever placed - $1.07). Are lock washers necessary, or just the washer and screw as shown in the Moss catalog? Oh, and do the screws need to be tightened down really hard or just "normal"?

And there's one of those small community airports about 10 miles away - will stop by one day when I'm in the area and see if I can get a "sample" of the Fuelube!

Sharon
 
[ QUOTE ]
Are lock washers necessary and do the screws need to be tightened down really hard or just "normal"?

[/ QUOTE ]

Sharon--

I only have locks on mine. And I made sure to use a small screwdriver so that I could not overtorque the screws during installation--the tank metal is pretty thin and could easily be stripped.
 
Thanks Michael! The gasket is in place, and the big test will be bright and early in the morning, with a trip to the Meguiars Detailing Clinic about 10 miles away, courtesy of PC of Jensen Healey fame!

Sharon
BN1
 
[ QUOTE ]
Are lock washers necessary, or just the washer and screw as shown in the Moss catalog? Oh, and do the screws need to be tightened down really hard or just "normal"?
Sharon

[/ QUOTE ]
Hi Sharon, just dismantled an original sending unit from my BJ7 and found "internal" lockwashers under all the screws. The gasket was a black thin fibrous (maybe paper) material. There did seem to be some type of sealant between the gasket and the tank, but it came off quite easy, could even of been paint. Good advise not to tighten too tight also. If you haven't already now would be a good time to run a ground wire from the sending unit to the cars frame.
 
healeygal,ive added lock washers to any sending unit ive changed if it didnt have them allready, ive never used any "sealant" but all the ones i found leaking had sealant on them, i replace the gasket with original fiberous ones and fit them "dry" and they never leaked,the big tip here has been mentioned several times " dont over tighten" also mentioned here the "ground wire" is a good idea. /ubbthreads/images/graemlins/yesnod.gif
 
Thanks all! I think we got it right - test run Saturday went great, and there is a ground wire in place. The test ride was to the Meguiars Detail Days seminar in Irvine, CA - got lots of good tips, a goodie bag and pizza, and saw John Loftus and PC (who gave me the invite to Jensen Healey Day at Meguiars, altho I may be in big trouble with some of the Jensen folks because I just noticed on top of the caption "We had a great turnout of some very nice Jensen Healeys..." on the Meguiars website is a picture of my car!) Oops!

Sharon
A Healey, but not a Jensen! /ubbthreads/images/graemlins/shocked.gif
 
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