Home » Public Forums » GMCnet » Dropping fuel tank to repair leak. (Considering improvements while I'm at it.)
| Dropping fuel tank to repair leak. [message #352251] |
Tue, 18 February 2020 14:43  |
Bill Van Vlack
Messages: 419
Registered: September 2015
Location: Guemes Island, Washington
Karma: 14
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Senior Member |
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Filled the coach last week and found fuel leaking at the front driver's side corner of Aux tank, from above the fill connection. Slow(ish) leak and eventually stopped after driving 5 mi and raising rear of coach. I'm home now, and planning to drop the tanks and figure out what's going on - once I find somewhere to pump the (50?) gallons of fuel.
In any event, I plan on replacing the rubber supply and vent lines with metal and moving the Onan supply from the Coachman tee to the GM stock location. Also splitting off the Aux tank vent and running it forward closer to the fill vent line.
So, one question is how to couple the new metal lines to the sender assembly. I have seen photos of 3/8" compression fittings and others showing short rubber nipples with hose clamps. I am leaning towards the rubber nipples - seems like good vibration isolation - and wondering if it's worth it to swage a bead on the ends of the new lines.
Another thing I am wondering is whether in-tank pumps are a good idea. Any issues with fuel pump cooling at low fuel levels? Also wondering whether leaving the two existing external EFI pumps as a backup makes sense - would they pull through the in-tank pumps?
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.
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| Re: Dropping fuel tank to repair leak. [message #352256 is a reply to message #352254] |
Tue, 18 February 2020 19:16  |
Bill Van Vlack
Messages: 419
Registered: September 2015
Location: Guemes Island, Washington
Karma: 14
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Senior Member |
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Thanks, Matt
I'd planned on extending the vent line as you described. Looking forward to that fill improvement.
I wondered whether the compression fittings might suffer/transmit vibration, and if a hose bubble on the end of the polyarmor and a rubber nipple might be a better approach.
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.
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| Re: Dropping fuel tank to repair leak. [message #352259 is a reply to message #352251] |
Tue, 18 February 2020 20:20 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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IF you use rubber hose pieces to couple to your new metal lines, You should probably put a bubble on the new line. If you do NOT install in tank fuel pumps, it is probably not necessary to 'bubble' flare the lines because there will not be any pressure involved, but it is probably good practice anyway.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Dropping fuel tank to repair leak. [message #352261 is a reply to message #352259] |
Tue, 18 February 2020 20:27 |
Bill Van Vlack
Messages: 419
Registered: September 2015
Location: Guemes Island, Washington
Karma: 14
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Senior Member |
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Carl,
Yes, just thinking about that. I found a post online that described using a double flare die..
Quote:On smaller lines, 3/16 up to whatever your tool will take, I use a double flare tool.
Let your tube protrude about (experiment) 2/3 of what you're supposed to for a double flare.
Use the insert and do the first stage only. Puts a nice uniform bulge right at the end.
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.
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| Re: Dropping fuel tank to repair leak. [message #352262 is a reply to message #352261] |
Tue, 18 February 2020 20:38 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Yes, that's how I did it. Just a partial double flare.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Dropping fuel tank to repair leak. [message #352266 is a reply to message #352262] |
Tue, 18 February 2020 23:02 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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On Tue, Feb 18, 2020 at 6:38 PM Carl Stouffer via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Yes, that's how I did it. Just a partial double flare.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Dropping fuel tank to repair leak. [message #352269 is a reply to message #352251] |
Wed, 19 February 2020 07:28 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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I would believe that leak you are seeing is the vent hose connection. That nipple off the tank, and the hose routing puts a little strain, and that is usually the first thing to fail. I have seen this on new fuel line installs, where all it took was a little tighting of the hose clamp. It is very important to use high quality hose clamps that you can get some good torque on, or once the hose shrinks a little, you will have that leak.
otherwise that hose tends to be the first one to crack right where the end of the nipple is on the other side of the hose clamp.
I am running the two tank pumps externally. I think there is enough pro's and con's to either intank, or exterior fuel pumps, it is all just what you feel comfortable with. I am also fine with rubber lines, as the trade off with going with metal, is adding some joints. Dropping fuel tanks, really is not a hard project. most of the work, is spent draining, and getting the coach up on the ramps/jack stands.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Dropping fuel tank to repair leak. [message #352271 is a reply to message #352251] |
Wed, 19 February 2020 07:55 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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In tank pumps and outside pumps? 4 pumps? To me that's kind of overkill. Anyway, if you do intank pumps, would it not make sense to also cut access holes in the floor to allow removal of the pump/gauge/vent assembly without dropping the tanks?
I opted for outside pumps on the 23' and the 26' has the single pump ahead of the selector. Both worked/work OK.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Dropping fuel tank to repair leak. [message #352329 is a reply to message #352271] |
Sat, 22 February 2020 16:01 |
Bill Van Vlack
Messages: 419
Registered: September 2015
Location: Guemes Island, Washington
Karma: 14
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Senior Member |
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I have another question.....
Our coach is a Coachman and has the Tee that Emory mentions here that states:
Quote:The first is in the GMC built coaches and is a dip tube near the rear left corner of the rear/main tank. The dip tube does not reach to the bottom of the tank, so running the generator will not empty the tank. The generator will run out of fuel and shut down as soon as the fuel level drops to the bottom of the dip tube. If you are below 1/4 level in the rear/main tank, the generator might not run because the fuel level is too low.
The second system was on coaches outfitted by other builders such as "COACHMEN". This system simply put a tee in the fuel line between the rear/main tank and the tank selector valve. The generator will run until the rear/main tank is empty. Then you only have left the 7 to 9 gallons that are in the front/auxiliary tank.
If I want to move the Onan connection to the tank, will I need to add the pickup as well, or did GM supply the tanks to Coachman with the pickup already installed?
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.
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| Re: Dropping fuel tank to repair leak. [message #352332 is a reply to message #352329] |
Sat, 22 February 2020 17:05 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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I also have a question regarding the fuel tanks. I am taking mine down to replace the hosing, and wonder if, after I release the straps, will the tank tip down on an angle and come out or is the flange on the tank going to catch the frame? Or do I need to also unfasten the bracket that the straps are mounted on and drop it straight down?
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] Dropping fuel tank to repair leak. [message #352333 is a reply to message #352332] |
Sat, 22 February 2020 18:40 |
Bruce Hart
Messages: 1501
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
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The straps are attached to the tanks. You will have to remove the three
screws that hold the bracket in place. If you have a floor jack and a
square piece of 2'x2' piece of plywood you can ease the tanks down after
loosening the bracket and J bolts.
On Sat, Feb 22, 2020 at 4:06 PM Terry via Gmclist
wrote:
> I also have a question regarding the fuel tanks. I am taking mine down to
> replace the hosing, and wonder if, after I release the straps, will the tank
> tip down on an angle and come out or is the flange on the tank going to
> catch the frame? Or do I need to also unfasten the bracket that the straps
> are
> mounted on and drop it straight down?
> --
> Terry Kelpien
>
> ASE Master Technician
>
> 73 Glacier 260
>
> Smithfield, Va.
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
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Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
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| Re: Dropping fuel tank to repair leak. [message #352335 is a reply to message #352332] |
Sat, 22 February 2020 19:35 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Terry- Straps are attached to the tanks.
you will take the 3 bolts that go through the cross member into the angle steel piece on the tank(attached to tank) out. Then take the 2 nuts off the j-hooks, and it will drop down a little bit. the filler hose will keep it kinda up there, and you will have to tip it down and pop it to the side to release it from the filler tube, then it will come down, and you can then worm up and get to the rubber hoses.
you have to take rear tank down, then the forward tank if I remember and usually install in reverse order.
installing, you will again fight a little to get the filler hose on and pop it into the filler hose then lift up. you want to get the J-hooks into the straps 1st, and put the nut on by just a thread. then lift it up and the 3 bolts will line up in the cross member.
tranny jack works well, as does taking the time to set up a sling system with ratchet straps. I use harbor freight 4 wheel dolly, and let them fall onto that, and can then roll them out from under the coach.
main thing that you want to be sure is to get all the fuel out if you can. or be prepared for the fuel to either slosh to one side making that side heavy quickly and the weight shift bad and it gets awkward handling, or worse the fuel sloshes toward the filler tube side, and that side gets heavy fast, and then covers you in gas. so jack the coach up a little and get all the fuel out of the drains. When I have done this job, I like using an electric fuel pump and pump the tanks dry. that seems to get 99% of the fuel out, better then just trying to use the fuel drains.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: [GMCnet] Dropping fuel tank to repair leak. [message #352336 is a reply to message #352333] |
Sat, 22 February 2020 20:03 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Thanks Bruce & Jon, I figured I was going to have to take that bracket off, but wanted to make sure. My tanks are over 6 feet off the ground and I'll use the rolling jack on the lift to catch the tanks. I ran the fuel down as far as I dared but there is always leftover fuel, right now the gauge says 1/4. At least it's not a full tank with a faulty pump in there! I'll probably get a siphon going after I disconnect the feed line from each one. That's the second time I've read to do the rear first, so even though that looked counter intuitive I will have to check that out again.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] Dropping fuel tank to repair leak. [message #352338 is a reply to message #352336] |
Sat, 22 February 2020 21:15 |
Bill Van Vlack
Messages: 419
Registered: September 2015
Location: Guemes Island, Washington
Karma: 14
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Senior Member |
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I understood that the Aux tank comes out first...
Any notion whether the Coachman will need an Onan pickup installed on the tank if one wants to change from the Tee off of the Main tank line?
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.
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| Re: [GMCnet] Dropping fuel tank to repair leak. [message #352339 is a reply to message #352338] |
Sat, 22 February 2020 23:12 |
Green machine
Messages: 184
Registered: July 2019
Location: North Vancouver BC
Karma: 5
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Bill Van Vlack wrote on Sat, 22 February 2020 21:15I understood that the Aux tank comes out first...
Any notion whether the Coachman will need an Onan pickup installed on the tank if one wants to change from the Tee off of the Main tank line?
Aux is front tank and it should come out first. The issue removing the rear (main) while the front is still in place is the middle of the 3 bolts is near impossible to remove with the front tank still in place. If it weren't for that it wouldn't matter unless I'm forgetting something...
Cant help on the second query. I've removed the Onan.
Shawn Harris
North Vancouver,
Canada
1977 Palm Beach 403
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| Re: Dropping fuel tank to repair leak. [message #352343 is a reply to message #352251] |
Sun, 23 February 2020 10:54 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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I probably have them backward. I am only pulling tanks out of a gmc every few years and I guess last time was a few springs back. I just know one blocks the other, like said above.
Make sure you replace with good quality stainless hose clamps and tighten them tight. Fuel lines will shrink and a cheap, not tight clamp will leak. Or at least that has been what I have seen. Don't use harbor freight clamps.
There are quite a few hose clamps needed.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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