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How do I stop fuel tank leak

Started by 52Cadillac, April 21, 2013, 08:40:01 AM

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52Cadillac

Installed new tank, new sender with gasket. No leaks until that night. Tightened, but didn't stop. Took to shop to replace gasket. I couldn't get a good enough grip on screws on my back from under car. All seemed good after replacing gasket, until the next night. Small leak again. Gaskets are rubber. I'm aware if over tightened it spreads around screw holes to allow leakage. Went over with guy at shop prior to replacement. Going back tomorrow. I used no sealers.
What type of gasket sealer would you use to help seal these troublesome gaskets? Any other tips?
SemperFiFund.org
(Helping combat injured Marines)

TJ Hopland

Not sure what the layout is here but guessing this is the type where the sender is always exposed to fuel vs the more modern type where its at the top?   I'm wondering if there is a problem with either the sender or tank flange?  One maybe is not flat?  Or its already been overtightened and the holes are now raised?   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Bob Schuman

Mike,
Your leak may not be a gasket problem. Gasoline will "wick" up along the threads of the five screws holding the sender, and seep to the outside. Making and installing a fiber washer between the sender and each of the screws will fix that condition. The gasket that came with my new tank and sender has holes that fit tightly around the screws, so no problem there. If your gasket does not fit the screws tightly, I'll bet that is the cause of your leak.
Bob Schuman, CLC#254
Bob Schuman, CLC#254
2017 CT6-unsatisfactory (repurchased by GM)
2023 XT5

52Cadillac

Ill check on it TJ.
Bob, Yours is probably the scenario being played out. If so, can I put a thread sealer on screws to seal em up. Maybe a lower hold threashold of locktite for threads? Any other sealant that may work? Taking back to shop on Monday, but want a solution prior to arrival, and any necessary supplies.
Wifey may make me park the Caddy in the driveway until resolved. Horrors. Humiliation. Depression. :-[
Mike
SemperFiFund.org
(Helping combat injured Marines)

Bob Schuman

Mike,
A thread sealer like Loctite may work okay. I didn't try that for fear that the sealer could get into the gasoline and cause other problems. If you just use a sealer on about the 3/8 inch of threads nearest the screw heads, that should not create any new problems. Little round gaskets are easy to make if you have a set of gasket punches, not easy if you don't.
Bob
Bob Schuman, CLC#254
2017 CT6-unsatisfactory (repurchased by GM)
2023 XT5

dplotkin

Just went through this yesterday with my 56. Put it up on a lift prepared to pull sender, re-gasket & seal screw threads. When I got it up I found all screws could take another full turn, some more than that. Gasket may have compressed over the two years it's been in. So I tweaked the screws & in a little while I'll go out and see how it worked and let you know.

Dan
56 Fleetwood Sixty Special (Starlight silver over Dawn Grey)
60 Buick Electra six window
60 Chrysler 300 F Coupe
61 Plymouth Savoy Ram Inducted 413 Superstock
62 Pontiac Bonneville Vista
63 Chevy Impala convertable
63 Ford Galaxie XL fastback
65 Corvette convertable 396
68 Chrysler New Yorker

dplotkin

It worked! yesterday I tightened the screws, not tight-tight, just snug, filled the tank, this morning, no leak. try that first.

Dan
56 Fleetwood Sixty Special (Starlight silver over Dawn Grey)
60 Buick Electra six window
60 Chrysler 300 F Coupe
61 Plymouth Savoy Ram Inducted 413 Superstock
62 Pontiac Bonneville Vista
63 Chevy Impala convertable
63 Ford Galaxie XL fastback
65 Corvette convertable 396
68 Chrysler New Yorker

R Sotardi #11719

I installed a new repro tank on my 50. Nothing but grief using the 1/16" gasket that was supplied. Called McVeys and they sent a thicker one , 1/8". Put a small dap of Gas & Oil Sealant (purchased at Ace) on each screw, but none around the gasket. Tightened the screws to about as much torque as I could get with my thumb & index finger. No leaks in three years. Ron

52Cadillac

Ok guys. We will give her a go tomorrow.
Ok thanks Bob.
Dan, what thread sealer did you use?
Ron, Ill give em a call in am.
Thanks, Mike
SemperFiFund.org
(Helping combat injured Marines)

dplotkin

Mike: I had a tube of "Seal-All" and a fresh gasket ready to install, but when I got it in the air I found all the mounting screws loose. So I snugged them (not too much) and did not use the sealant or new gasket & the leak stopped.

I went through this exact same thing with my 65 Corvette which has a "wet" fuel sender like the Cadillac. The Corvette senders are on the BOTTOM of the tank since there is no trunk. It seeped from one of the sender electrical studs. I snugged the bolt & it stopped.

If the Caddy leaks again I will use the sealant (which I bought at Advance Auto), but I'd rather not if I don't have to. Try snugging the screws.

Dan
56 Fleetwood Sixty Special (Starlight silver over Dawn Grey)
60 Buick Electra six window
60 Chrysler 300 F Coupe
61 Plymouth Savoy Ram Inducted 413 Superstock
62 Pontiac Bonneville Vista
63 Chevy Impala convertable
63 Ford Galaxie XL fastback
65 Corvette convertable 396
68 Chrysler New Yorker

52Cadillac

Dan, I personally tried snugging up the screws cross pattern a couple times, and it didnt work.
I dropped her back off today. Mechanic asked me to find a cork gasket for him. Told him a no go, and handed him some thread sealer. Will order extra thick gasket from McVeys. Hopefully today's fixit wil hold.
Mike
SemperFiFund.org
(Helping combat injured Marines)

Walter Youshock

Why not just go to your local auto parts store and buy a roll of cork gasket material and make your own?  You'll get enough material to make 10 of these gaskets and save time and money in the long run. 

I bet 30% of the gaskets on my car I made myself just because I didn't have time to wait for somebody to send the wrong part...
CLC #11959 (Life)
1957 Coupe deVille
1991 Brougham

52Cadillac

Walter, Yes I was thinking that I might be able to do so, never done it, but shouldn't be a biggie..hahaha. I know I could use the rubber gasket as a template. How would I punch out the holes, and to the correct size?
Thanks, Mike
SemperFiFund.org
(Helping combat injured Marines)

Walter Youshock

All you need is an X-Acto knife or a razor blade, a pair of scissors and a hole punch as found in office supply stores.  I also have a set of punches for larger holes but you don't want to make the holes TOO big.  Oversized holes may be your current problem.  Oh, and the roll will not want to lay flat.  You may have to iron it or it'll keep curling up.

One other thing:  you may have to run an external grounding wire from the sender to the frame of the car or the gauge won't work. 
CLC #11959 (Life)
1957 Coupe deVille
1991 Brougham

66 Eldo

I have installed new or re-installed old rubber gaskets using Vaseline to help seal.

52Cadillac

Thread sealer failed to seal tank completely. I still have an annoying minor leak, and I still cant smoke my cigar around her.

Sounds good Walter. Ill see if I can find some cork material, or heavy paper type to make one. My only concern is making holes small enough for screws to be a good fit. Ill figure that out. Ill call around today to see who has some gasket material locally. I think the sender is grounded to the tank. Gauge Seems to be working fine when I filled her the other day. It didnt work properly with the old aftermarket tank I removed. I know what you mean with wrong parts, or parts that don't work, or wrong size, etc.

Dan, was that gasket from McVeys cork, paper, or rubber?

Eldo, I might've tried Vaseline. Except this is my fourth attempt to seal the tank. Now I'm on a mission to acquire a better gasket for this purpose.
Thanks, Mike
SemperFiFund.org
(Helping combat injured Marines)

dplotkin

Mike: My gaskets are rubber, the one installed in the car (which is a re-production tank) is rubber. I have rubber washers behind each screw head too. Can you determine exactly what is leaking? Is it seeping from around the gasket? Is it seeping from the electrical terminal stud? Or is it leaking from around the screw heads?

If you make a gasket, you want the screw holes as small as possible, poke holes with an awl. But I think I'd start over, using a fresh rubber gasket and rubber washers behind each screw head, using sealant on the threads of each screw.

Dan
56 Fleetwood Sixty Special (Starlight silver over Dawn Grey)
60 Buick Electra six window
60 Chrysler 300 F Coupe
61 Plymouth Savoy Ram Inducted 413 Superstock
62 Pontiac Bonneville Vista
63 Chevy Impala convertable
63 Ford Galaxie XL fastback
65 Corvette convertable 396
68 Chrysler New Yorker

The Tassie Devil(le)

Whatever you do, don't use plain ordinary Rubber.   Use Neoprene, as the petrol will eventually destroy rubber.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

R Sotardi #11719

Bruce is right! Any material that is in constant contact with gasoline (petrol), must be made for that. OK, cork originally used. My feeling is that eventually the coating is attacked by the new fuels, maybe not, but, I have observed many Model A Ford owners ( including me)  replace their fuel tank floats as the cork  deteriorates in the tank and falls off or loses it bouncy.  New "rubber" is NOT neoprene  it is most likely Buda rubber. So this is what you need to purchase if you make your own. Go to McMaster -Carr and check it out. Mcvey sells 1/8 " seals with the correct diameter holes, however they wanted $10 ea. For $10 who needs grief?  BTY, you may have a problem with the ground  for the fuel gauge when you add sealant.

52Cadillac

Ok did manage to have my Fav Gal pick up cork gasket roll. That was all I managed to do after dinner and strawberry shortcake along with a drink. So tomorrow ill make a couple gaskets to take over to the shop, and have em install one. Ill pick up some rubber washers or make em from cork, and make sure they use sealant on threads again. Damn thing is annoying. Now my paint on tank is screwey from gas dripping. Oh well. Ill repaint later.
Thanks, Mike
SemperFiFund.org
(Helping combat injured Marines)