Fuel tank

petarm1 · January 10, 2020, 04:55:33 AM

Noticed today that it looks like i have a small leak in my fuel tank on my 89 mci 102. Any suggestions on the best way to locate the leak do a repair?
Thanks

buswarrior · January 10, 2020, 06:43:41 AM

Drain it, remove and repair.

There are no short-cuts.

Aluminum welding.

Note the close clearances, your welder has to know not to increase the size with a patch, or it might not go back in.

Happy coaching!
Buswarrior

lvmci · January 10, 2020, 07:31:15 AM

Hi pretarm, leak in the bay or on the ground?

Utahclaimjumper · January 10, 2020, 05:40:37 PM

Double post

Utahclaimjumper · January 10, 2020, 05:41:35 PM

Very carefully clean the top where the fuel and return lines exit,, Years ago I thought mine had a leaking bottom with fuel on the floor.. After the agony of removal,, found no problems on the bottom but,, found the leaking was at the top ( at a fitting ) and running down the backside and onto the floor..>>>Dan

petarm1 · January 11, 2020, 05:52:43 AM

Thanks for the help. Looks like it is leaking on the ground. Bus has not moved in a year now since i live in it full time. It also looks like there is some fuel coming out from a belly pan under the center of the bus that goes about have way the length of the bus. Going to wash around the tank this weekend if the weather improves to look at it closer. Again thanks for the suggestions.

Brian Diehl · January 11, 2020, 08:27:52 AM

I went through this on my 96A3 back in 2015. Unfortunately I had an almost full fuel tank when I noticed it had started leaking. I siphoned all the fuel out into 35 gallon garbage cans lined with construction quality trash bags. I then pulled the fuel tank out and discovered a leak on the bottom of the tank where it had been moving ever so marginally and in the process the accumulated silt/sand under the tank acted as sand paper. The original material between the fuel tank bottom and bay bottom was plywood. The plywood had deteriorated over the decades and combined with the sand paper action of the sand/silt underneath the tank had warn through the aluminum.

There were several thin areas in the bottom of the tank. I had a local welder guy weld in a large patch over the entire thinning area.

Hopefully the pictures will help with picturing the process. It wasn't difficult, but it was messy and time consuming.

Brian Diehl · January 11, 2020, 08:28:49 AM

more pictures

Brian Diehl · January 11, 2020, 08:29:17 AM

The empty fuel tank bay...

DoubleEagle · January 11, 2020, 08:41:25 AM

That MCI arrangement of coming out on the side is certainly much more convenient than coming out in the middle of the rear of the last baggage bay on Eagles. I wonder if it would be a good idea to put a heavy rubber mat on the floor, like the ones used for horse pads in stables. I think they would hold the tank better, they should not rot, but I wonder if leaking fuel would affect them?

buswarrior · January 11, 2020, 08:50:23 AM

Temporary fuel storage for this job, plastic tote, barrels , both metal and plastic, an old home heating oil tank... something with a valve for ease in putting it back when you are done... course, if it keeps leaking, there won't be much to store...

Watch the clearances, some coaches, the fit is really snug. Both the new wood you put in the bottom of the tank bay, (yes, renew that soggy patchwork of rotting wood) and any patching, can, and has, prevented the tank from going back in!!!

Don't think you can go any thicker than that hardboard that is in there, and your welder needs to know to make the patch snug...

The tank may need help to come out, the aux tank plate on the bottom sits in a recess, most all tanks have the plate.

A piece of thin 1/4 plywood driven under the tank will raise it enough to come out of the recess. You can't leverage it out by hand, no room to tilt. The piece of ply has to go close to half way back to "lift" the right place. A chain through the filler neck and out one of the block-off plates and a pick-up truck is also handy...

If you have fuel migrating up high into the baggage bays, best do more diagnosis, that may be a fuel line or fitting leaking, and not the tank.

Happy coaching!
Buswarrior

dtcerrato · January 11, 2020, 09:00:44 AM

Hi Brian, wow you sure salvaged that tank with all the work on it! GM fuel tanks are also sitting on a 3/8" sheet of plywood. Any rubber product would eventually be adversely effected by fuel oil unless it were nitrile. Brian's mention of sand & silt would always be a culprit no matter what media the fuel tank platform is. More effective would be to secure the tank so no movement can occur. The GM tanks are strapped down super tight at tank baffle areas & ends (5 total). Metal straps also have cloth softeners. When we pulled our tank there was a small pinhole - JB Weld has been successful for several years now.

lvmci · January 11, 2020, 02:20:03 PM

Hi petarm, my C3 and my 5A, I think, had 3 lines from the tank bottom to the center raceway to the engine, with a stop at the auxiliary tank, there are elbows in a few places, if the leaks continue from the center of the frame, lvmci...

petarm1 · January 14, 2020, 04:23:10 AM

I have remove,d the fuel for now and will have to wait for the weather to change before i continue. Great pictures brian and as always great advice from all.

chessie4905 · January 14, 2020, 05:17:21 AM

Be a good time to remove and clean all the sludge lying in the bottom of the tank. Save on fuel filters down the road.