Author Topic: Gas tank leaking (Read 18951 times)

Donmystic1 · « **on:** June 06, 2016, 12:47:56 PM »

Just finished the paint job on my 1991 BMW K1.
I reinstalled the tank and put about one gal of gas in it.
Once the new fuel pump primed the system the bike turned over for 5 secs and fired right up with no issues after being stored for 7 years.
While the bike was running, I noticed a drop of fuel on the bottom left side of the gas tank.
I dried it off and within 30 seconds another drop appeared.
Turns out I have a pinhole leak on the bottom seam, right underneath where the fuel pump sits.
I am afraid that if I grind it down that one pinhole will turn into many.
What methods have the members used to seal the seams of the tank.

Don

Chaos · « **Reply #1 on:** June 06, 2016, 03:08:01 PM »

I've used JB weld and Permatex fuel tank repair, had the best luck with the Permatex. I'd sand the outside down and apply it inside and out.

Donmystic1 · « **Reply #2 on:** June 06, 2016, 03:22:42 PM »

Thanks,
I can't see the seam as it is under the fuel pump.
I am going to try POR 15 and squeeze it thru an old mustard bottle.

Elipten · « **Reply #3 on:** June 06, 2016, 07:59:24 PM »

Aluminum welding. Grind the oxidation out, take to a pro welding shop and get it aluminum welded. The location on the left side dripping onto a hot motor is just bad juju for a fire between your legs. I
Iike my lower extremities just the way they are.

Martin · « **Reply #4 on:** June 06, 2016, 08:07:57 PM »

I bought some aluminium solder the other day. But due to the fact that you would be using a propane or oxy torch, tank would have to be really well flushed and/or filled with inert gas. I have not tried it yet.
Regards Martin.

Donmystic1 · « **Reply #5 on:** June 06, 2016, 08:31:26 PM »

I disassembled the guts of the tank and am now etching the corroded areas with POR etching solution.

Tomorrow I will use a mustard bottle and coat the areas where water sits and let it dry for several days.

technostructural · « **Reply #6 on:** June 09, 2016, 09:22:11 AM »

I sanded it down, used JB Weld's "Waterweld", sanded that, primed it, painted it, and it has been fine for a year so far.

Given that it is on the bottom left corner, and under the fuel pump, you won't be able to put any JB Weld / Permatex, etc on the inside. I suppose you could if you removed the fuel pump entirely, etc. Otherwise, you will have to settle for the outside only.

Once I had it sanded down and I could see the pinhole, I took a nail and lightly tapped the hole a bit bigger. This will feel awful and wrong when you're doing it. This allowed me to push that JB Weld into the hole a bit and hopefully form a bit more of a seal.

Anyhow, people have different preferences on what to use, but the JB Weld "Waterweld" is designed for aluminum fuel tank applications.

Given that the repair is so low on the fuel tank, you can also get away with less-than-perfect paint work, which is kind of nice to not worry about.

Donmystic1 · « **Reply #7 on:** June 09, 2016, 09:31:31 AM »

I have gutted the fuel tank of the pump fuel lines and fuel filter.
I used the POR 15 metal etching solution, washed it out dried it and poured
the POR 15 in all the lower seams used an old mustard squeeze bottle.

Now I have to wait for 5 days for it to dry.

Thanks for all your suggestions.

Don

jay1622 · « **Reply #8 on:** June 09, 2016, 10:52:19 AM »

Following this thread as I get ready to etch and diagnose my fuel tank for my rebuild. Do you guys think I am looking at one large repair failure or that and quite a few others?

Donmystic1 · « **Reply #9 on:** June 09, 2016, 11:04:55 AM »

Looks like a POR 15 job to me. Methodically, follow the three steps .

jay1622 · « **Reply #10 on:** June 09, 2016, 11:35:37 AM »

Fixing to sand the whole thing down... Wondering if I shouldn't just go the weld route.

Elipten · « **Reply #11 on:** June 09, 2016, 12:49:15 PM »

Check the entire seam on the left side of the tank

Just remember where the hole is the surrounding metal could also be thin. I know Ted Porter would send them out for welding in the past from personal communication many years back.

If storing the bike for a period, drain the fuel and store upside down with cap off. Put pump in kerosene.

Laitch · « **Reply #12 on:** June 25, 2016, 08:15:40 AM »

Quote from: Elipten on June 09, 2016, 12:49:15 PM

If storing the bike for a period, drain the fuel and store upside down with cap off. Put pump in kerosene.

"Let me show you the remodeled garage. That's my old K100 hanging there. Watch out. Don't hit your head on the handlebars but if you look closely, you'll see a family of barn swallows living in the tank."

Brahma · « **Reply #13 on:** June 25, 2016, 08:39:30 AM »

My tank sprung a leak 20 years ago, right where the rear mount attached. I took it to a fabrication shop and had it welded. Its been fine since.

Donmystic1 · « **Reply #14 on:** September 07, 2016, 08:41:45 AM »

I have had the tank coated with POR 25 for about two months now. Seems to be sealing the tank just fine.
I have put about 150 miles on the K1 since then with no problems.

Mwilson904 · « **Reply #15 on:** September 07, 2016, 10:02:06 PM »

The bike I got sat for 12-13 years, All my tank innards, pump, damper, etc will be here Friday.
I noticed that someone had applied a paint to the outside of the seam at some point.
Many years ago, I had use some white milky stuff to line the entire inside of a tank (standard tank not bmw) maybe I should postpone the reassemble and use some of the Por stuff at least on the inside of the seem.
I can see that someone had painted the exterior of the seem black, my neighbor had bought the bike with 7k miles in 1995ish, and doesn't remeber ever having a leak, but then again like myself he lost many brain cells in the 70s and 80s

Donmystic1 · « **Reply #16 on:** September 08, 2016, 05:49:35 AM »

Make sure that you clean the inside really well using the POR Etching solution.
Follow the directions to the "T" and you should not have any problems.
Online or NAPA carries the product.

Good luck

Don

Brad-Man · « **Reply #17 on:** September 08, 2016, 12:01:19 PM »

I hear Caswell has a good tank liner product that many swear by too.

kennybobby · « **Reply #18 on:** September 08, 2016, 01:22:12 PM »

@Mwilson, it looks like you have a blister in the paint/pinhole leak forming, visible at the far right edge of the photo. The seam and area to inspect is the lowest points that water would collect, which is the seam aft of the supply port on the left side.

Mwilson904 · « **Reply #19 on:** September 11, 2016, 09:07:05 AM »

Thanks Kenbobby, it appears someone had applied something to the exterior so I'm guess there was a leak at some point, I have everything out of the tank so I reckon now would be the time to use some type of liner like por15 just to make sure it doesn't further develop.
Should I cap off the lines and coat the entire interior, or just use it to fill the seems which seem to be the main culprit for everyone?

kennybobby · « **Reply #20 on:** September 11, 2016, 09:52:18 AM »

i'm going to try to fill and cover just the bottom seam areas on my bike with either redkote or some sort of aircraft epoxy made for aluminum fuel tanks, e.g. 3M AC Tech 240,

but if the interior tube ends were covered with rubber plugs then i would guess the entire interior could be done. If it were steel i would solder the pinholes and coat the entire tank.

Martin · « **Reply #21 on:** September 11, 2016, 01:04:35 PM »

Kennybobby you can get aluminium solder, I am currently trying to get the hang of using it with limited success. I have tried a propane torch but was unable to generate enough heat. I then tried MAP gas which was better and I had limited success. I have come to the conclusion either my solder has too high a melting point, the aluminium is too thick 3mm or I will have to break out the Oxy Acetylene. I will check today to see if I have the right solder, and go from there.
Regards Martin.

kennybobby · « **Reply #22 on:** September 11, 2016, 05:53:08 PM »

Oxy-Acetylene gets so hot and aluminum doesn't show any color like steel--i've melted through some aluminum years ago trying to use a torch so i'm once bitten twice shy.

Martin · « **Reply #23 on:** September 11, 2016, 06:24:29 PM »

:2thumbup: Thanks Kennybobby I'm just paying with scrap to see if I can do it for possible future repairs.
Regards Martin.

kennybobby · « **Reply #24 on:** September 11, 2016, 06:53:02 PM »

If you figure it out Martin, be sure to post up the secret...

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Author Topic: Gas tank leaking (Read 18951 times)