Leaking Fiberglass Tank

Fritz · Sep 10, 2008

Hello all! I've been watching the Forum for some time now and am very impressed with the wealth of knowledge that resides here.

I have a problem with an old fiberglass fuel tank. I carefully applied the Caswell sealer last month. At first it seemed all was well, but now the tank is weeping on the underside in one corner. My Question: Has anyone ever applied Caswell a 2nd time with any success. Thanks in advance to all who might share their experience!

aceaceca · Sep 10, 2008

I don't believe in that stuff. If you take a dremel with a little burr wheel on it and clean up the leaking spot, then apply either fiberglass stuff or I used some old Devcon paste epoxy. Problem solved.

mikie3117 · Sep 10, 2008

Hello. I have the same problem with a 1970 fastback tank. I used Kreme initially

and now have a "soft spot" on the bottom that leaks. I do not think that there is enough good material to use a dremel and an external patch but it might be worth a
try. Let us know how your turns out first :wink:
Mike

Yellow_Cad · Sep 10, 2008

Fritz, my experience was just like yours. I have a fiberglass Interstate tank. Sloshed it once with the Caswell stuff and it leaked. Sloshed it the second time and it working fine. I believe the Caswell stuff is perfect for fiberglass tanks but not so sure about the metal tanks. There is a great post that I and others participated in that is on this forum or Brit Bike forum on this very subject that should tell you all you need to know.

Yellow_Cad · Sep 10, 2008

Mike, from my experience with the stuff, I believe that you could support the soft area with tape and slosh with the Caswell stuff 2 or 3 times and have the integrity you need.

Fritz · Sep 10, 2008

Thanks to everyone for the quick replys. I contacted Caswell today and posed the question to Cindy Murphy, who runs the online "chat" service at their website....cool. I actually received an email reply from Mike Caswell himself which read:

Wash out the tank with a small amount (pint or so) of laquer thinner, pour out remainder and allow to dry. Place a pound of drywall screws into the tank and shake vigorously to scratch up the inner surface. Then, carefully following the directions, re-apply 2 coats to insure a good seal.

Ordered the Caswell sealer online today...I'll report back with the results next week.

Yellow_Cad · Sep 10, 2008

The big thing with the two part Caswell solution is to get the mixture proportions correct. If you use the entire portion of each as I did for the large Interstate tank, then there shouldn't be a problem. If yours is a Roadster, you may need to watch this.

mikegray660 · Sep 10, 2008

(not to) secrets for success...
yes the wash it and use the nails etc, as mentioned mixing the stuff correctly is critical
BUT - but i've found that coating the tank and then recoating it again within 24h before the stuff really hardens works best - i've done about 4 tanks now and this is the only way i have found to avoid the same problem you have seen - while the dremel tool and a patch might seem like a solution its only temporary as the fiberglass will get eaten away else where and you see it all over again -i had a pro fiberglass repairs on an interstate tank and it developed leaks elsewhere before the 2x treatment

m

72Fastback · Sep 11, 2008

My tank has started to leak as well... The Caswell stuff is definetly the best you can get for the fiberglass tank, yes? From what I have read, there is nothing better, but just want to double check before i buy some.

BillT · Sep 12, 2008

I used the caswell stuff on my Fiberglass Roadster tank. As far as I know, the tank had not had any fuel in it for many years. I followed the procedures - cleaning the tank, shaking the tank with screws inside, mixing 1/2 part A with 1/2 part B (2 applications) - and let the tank sit for about three months before I put gas in it. The 10% ethanol they sell here softened up the caswell stuff within a day.

Mike Caswell stated that he was going to send me a stronger mix, but that hasn't happened. I got the steel tank.

72Fastback · Sep 12, 2008

Well, I live in North Carolina, does anyone know what amount of ethanol they put in our gas, if any at all?

Fritz · Sep 13, 2008

First place to look is the gas pump where you get your gas. All the pumps in Florida now, or will soon by law, sport a sticker that reads "Contains minimum 10% Ethanol".

Fritz · Sep 13, 2008

BTW...a question to those who have done the Caswell treatment on their tanks:

How did you protect your petcock threads during the treatment? The Caswell site instructions say to remove the petcocks and use putty or Play-Doh, although I can't see how this would work without getting some of the putty/play-doh lost in the tank? I'm wondering if they should they stay in during the process? Thanks in advance for any feedback.

BillT · Sep 14, 2008

Fritz said:
BTW...a question to those who have done the Caswell treatment on their tanks:

How did you protect your petcock threads during the treatment? The Caswell site instructions say to remove the petcocks and use putty or Play-Doh, although I can't see how this would work without getting some of the putty/play-doh lost in the tank? I'm wondering if they should they stay in during the process? Thanks in advance for any feedback.

When I did my tank, I used rubber plugs, like one would use to blank off a vacuum fitting. I keep stuff like this laying around my garage.

If I were to use a putty, I would place some saran wrap over the hole first, then stuff in the putty. No chance of putty falling into the tank this way, and you're supposed to use saran wrap to cover the gas inlet, anyway.

maylar · Sep 15, 2008

I use 1/2-20 bolts and the petcock sealing washers. After treatment and draining the remaining sealer I wipe the threads with Q-tip and laquer thinner. When totally dry I ran a 1/2-20 tap through the threads. Seems to work for me.

debby · Sep 15, 2008

maylar said:
I use 1/2-20 bolts and the petcock sealing washers. After treatment and draining the remaining sealer I wipe the threads with Q-tip and laquer thinner. When totally dry I ran a 1/2-20 tap through the threads. Seems to work for me.

I did the same and it worked for me too. The threads are actually BSPP, not UNF, but the 1/2-20 UNF seems to be close enough for this purpose.

Debby

Fritz · Sep 15, 2008

Thanks maylar and debby....the technique you describe sounds like the way to go. Gotta love this site and the fine people who contribute!

batrider · Sep 15, 2008

It's really a 1/4" - 19 BSPP parallel pipe thread. Tap available from McMaster-Carr 8328A22 for $17.15.

Leaking Fiberglass Tank

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