When I first got my car, 6-7 years ago, the sender was bad, and I replaced the sender and the tank. I planned to install efi, so I removed the fuel suction tube from the original sender, cut it down, and had it brazed into the new one, and I capped it off.

I did clearcoat the tank before install, much of the staining on the bottom, and the top as well, is probably from fuel degrading the paint.

From day one, the new tank leaked if I filled it full. Easy enough to deal with, just don't do that. For 6 years, I'd run it down to empty, then put 10 gallons in and call it good.

With the "restification" of the car nearly complete and the Billings run coming up, I want to be able to put in 18 gallons and have them stay there.

Here's what I know: If, and only if, the tank is above 3/4 full, fuel drips from the lip on the front, pass side, just inboard of where the lip is bent up at the corner. It drips pretty quick, drip two three four drip two three four. I once put a container under it, it lost a quart of fuel in 2 hours.

So I drained it and dropped the tank. (note: if you jack the back of the car up a foot, take the input hose off the fuel pump, and put it in a bucket, every single drop of gas WILL siphon out of the tank, and you don't even have to suck on the hose.)

Here's some pics.

It does not appear that it was leaking at the sender gasket. If fact, the entire recess where the sender goes is clean, not discolored, no residue, nuttin. There was some road grit but it was loose and vacaumed right off.

There is considerable evidence of some sort of liquid sitting on top of the tank. There is evidence of liquid sitting most of the way around the lip, dripping down the front of the tank on both sides of the sender well, but the sender well itself is clean as a whistle.

Where the return tube is brazed onto the sender (brazed on the bottom, inside the tank) there is a lil section, maybe 3/16", where the weld is incomplete, sorta shown in pic sender2. Directly above, there is a little rust spot on the top surface of the sender.

What's leaking, and how do I seal it?

Buy an NOS one. They're still available.

Jim, when I looked at the picture of the sending unit, it looks like the leak might be at one of the tubes (return tube) instead of the tank itself. Also since the leak is coming off the back passenger side of the tank, I suspect that the gas is running down the tube (return tube) and dripping onto the tank at that point. Try using some JB weld to seal up the area around the tube and see if that helps. I think like you said that the rust is a good indicator that gas has been leaking from that point for awhile.

Some JB weld around that area is on my list then, tho I'm not sure how and with what I'll get in there to clean it up first.

I'd suspected that tube before, it does look like fuel was running down it, but 2 weeks ago I replaced the hose and bolt I had plugged it with, no help. The return is not currently being used.

Tony, NOS what? Tank? 2 peices of metal welded together in the middle, it's not leaking in the middle. Sender? the sender works fine, and even if I got a new one, I'd still put a hole in it and a return tube. This car will run EFI someday. Regardless, the tank will be back up and the car back on all 4 by dinner tonight. Not exactly a helpful reply.

Got a vaccuum cleaner that has a blow function?
Block off all hoses...the hoses end leaving the the hoses connected to the tank.
Presurise the tank, with vaccuum cleaner and a damp rag sealing around the 'cleaner tube in the tank.
Go around all joints hoses etc with a stethoscope listening for air leaks.

This also is a quick method to 'pop' a fresh dent in a tank.

Do NOT run the vaccuum cleaner on suck in the tank!!!! BIG BANG and resulting in a very quickly dismantled vaccuum cleaner
Jim I realese u are not stupid enough to do something like that...thu others may do it without thinking....

Pressurize the tank with your air compressor (seal it the best you can) and grab a bottle of dish soap and water in a spray bottle. Spray it around all the seams and look for the bubbles. Just like you would a tire looking for leaks.

I epoxied up both side of where both tubes go thru the sender.

Tomorrow I'll try a pressure test of some sort and see what happens. Kinda bugs me, around the sender is clean as a whistle, and how the heck did the very top of the tank get all messed up?

Anyone else got an idea on where it's leaking?

So this morning I set to put some pressure in the tank and see what I got.

I use a bunch of baby food jars hun beneath the cabinets above mny workbench to hold nouts and bolts and things. The smallest size fits right into the filler hose and seals like nobody's business. I atached an air line to a peice of 3/8 hose, put that on the fuel out tube, and pumped her up a bit.

She leaking like a sieve through the bushing where the wire passes thru the top of the sender. Gooped it up with epoxy, will try again in a couple hours, up to my neck in honeydo's for now.

Maybe an NOS sedner wasn't such a bad idea after all.

Even if its leaking thru the sender somewhere, there must be a leak in the tank itself, or one of the metal lines on the sender if the leak stops with less than 3/4 of a tank of gas. How would gas leak out the top of the tank except when it was full.

I'm betting there is a pin hole in either the metal supply fuel line or the rubber connector to the lines attached to the car somewhere near the left front corner of the fuel tank. Supply because its under vacuum while the car is running, so you wouldn't have a leak with the engine running, but it does extend into the tank so it will siphon fuel out of the tank. Unlike the return which is underpressure with the engine running, and you would have a leak both with the car running an not running but only enough to drain the return line, since it doesn't go deep enough into the tank to siphon gas out of the tank.

if there is a leak in the tank, I'll find it.

It could be the return line, which is actually the fuel supply line from the original sender. It's very old, though nothing leaked beofre I replaced the tank 6 years ago. Note the return is not currently being used, it is capped off. It does extend 1" into the tank (3/4 full??) and where it is plugged (with 3" of hose, a 3/8 bolt, and four clamps, all new a month ago), the first joint is below fuel level when the tank is full.

I'm hoping it will hold pressure once that wire pass through is sealed.

edit: Wonder if I should just leave it till Tuesday and spend a hundred fifty on another repro tank and sender? I'll lose my return line, but I haven't used it yet anyway.

When I was last at Classic Ind. they had some real nice stainless tanks. Not bad price either about $160.

Jim,
I am not sure if this will help, but you said that you blocked off the "return" ?? Is there still a vent line ? If not, do you have a vented cap ?? If the system is supposed to be vented through the extra line, and you have it blocked off, when the fuel heats up it will expand and force itself out somewhere. The fuller the tank is, the worse the problem. Dont know if this is the case here, but figured I would mention it.

I do have a standard vented cap, Bill.
The return line was for a "future efi installation"

I put 5 psi of air in the tank, 45 minutes later there was still pressure in it. It's back in the car now. Next time I need to make a long run somewhere, I'll fill it to the top and see what happens.

Well, I drove the vert to work today, because I had an appointment to get a custom boot cover made, or I thought I did, turned out that's next Tuseday.

So a customer in Platteville Wisconsin calls with an emergency. Course, threat of thunderstorms or not, I'm there. Carol of course knows I need to take care of my customers first (hehe) so I saddle up the vert and cruise off to dodge thunderstorms for a 400 mile round trip.

Good news is I filled er up to the top twice, and didn't leak a drop of gas.
She's still giving me 19 mpg.
Ran like a top, all the way there and all the way back.

And the wipers work for sure.

'bout an hour after I got there, it started raining. Not one of those scattered thunderstorm type of rains, an "I'm gonna be doing this for a while" kinda soaker. I got the top and the windows up, and it only took one roll of paper towels to mop up the interior. 2 hours later when I leave, it's still coming down. Didn't stop till I got home four hours later.

The wipers work good. The defoggers almost do.
Why does the defogger clear the windshield but fog up the back window?

And for icing on the cxake, my Kenwood quit on the way home. The display lites up, changes stations, stereo indicator comes on, even selects cd's, but not a sound comes out. not out of the 4 speakers attached to the amp, not out of the 2 run off the stereo either.

Think this one's a no brainer, stereo will come out tomorrow and get sent to someone who can fix it and get it back to me before Billings. Anyone know of such a place? When I needed to fix the cd changer, the place I sent it took 2 months to send it back.

So it sounds like every thing is working as it should then.
didn't leak a drop of gas.
Fixed.
'bout an hour after I got there, it started raining.
its water proof
The wipers work good.
Why does the defogger clear the windshield but fog up the back window?
Because the demister is in the front, the rear window in the back..meant to be that way...who needs to know where ones been? its what up front that matters lol
Kenwood quit on the way home.
Good ..so u can listen to the music of a well tuned Chevy engine ...way to go.

Jim ya sound sorta flustered so don't take this wrong. I would send your kenwood to the radio guy that's on T/C or Team Chevelle. Not sure what his nick is. i would then buy a $80.00 or so head unit at Walmart or what ever and mount it under the dash for your trip, you will have AM/FM and single cd. You can mount the din box with screws that hold the lower dash part on the center or the ash tray screws. I had one mounted there for years and covered the sides with a black plastic. Almost out of sight in that area and still did not have to cut my dash and had a nice high powered Pioneer unit with sub out and amp controls cross over and remote control for $260.00.

A quick cheap fix for ya and you get the Kenwood repaired the right way. I think his name is Radio Joe or something. You can always keep the el cheapo untit for another time or get a converter and mount it in your work bench in the shop. I found car stereos work well in the shop with an old antenna mounted on the roof and some book shelf speakers.

Joe

I'll put a post on Team Chevlle too, but any idea who the guy is Joe?
And are you suggesting he might take a while to git-er-done?

I think it might. If i remember right he took awhile but does quality work.

Check this post, it has some links in it http://www.camaros.net/forums/showthread.php?t=41459&highlight=radio+repair

Check the web addy under Radio Joes sig also

naaa, I'm not flustered. Was a great day to cruise in the vert, in spite of 4 hours at highway speeds in the rain and a lack of tunes for the last hour.

My kiwi buddie, you are sooo right. All is good without a doubt. It's still amazing to me how well I've made this car work. Show cars, trailer queens, museum pieces all have their place, but my car is a driver first and foremost. It's reliable, solid, smooth, and fast, and seems to do everything very very well no matter what nature and I throw at it, and not measuring by a 38 year old yardstick, either.

The radio will get fixed.

I look back over the last 26 yrs with mine...
Full rebuils in 86...things like brake cylinders got replaced whether needed or not..didnt even both checking.
Since then..other than tyers, battery type stuff..
Replaced :
Fan and wiper switch, radiator, top water neck, couple tie rods, pitman arm, heater fan, water pump fan clutch, a water pump, and replaced orginal alternator with a self reg one. Oh and the dip switch and heater radiator
30 yrs of daily running..thats pretty minor maintance, and she has NEVER broken down.

3 body repaints/ cut small bits of rust rebuilds since then...and also at these times replaced orginal stuff like dash pad, carpets, hood liner, dash pad, broken air vent slider. door lock knobs, window winder handle, door/trunk etc rubber.
Uphostery even today is still orginal and in orginal condition, put this down to using Pledge and sheep skin seat covers.

Our Camaro has had far less and cheaper maintence/reliabity than any computerised , fuel injected, plastic, cam belt, cv joint heap of modern crap, less than 1/4 its age and 1/4 milage...
except for the seats...its a damn sight nicer car to drive to.
Seats are being swaped at the moment for 1988 subraru Omega seats. Damn near bolt straight in ...almost the same shape and give more leg room in the back and wider opening to the rear.

The defoggers almost do.
Why does the defogger clear the windshield but fog up the back window?

Chevy knew that very well - that's why these were extra-cost options :D

Damn I forgot..I used to have one on the back window...but before I got the car it never worked so I hooked up the radio to it...
That worked as an aerial for about another 15 yrs, but by then it was looking pretty crappy and removed it lol

Jim, no leaking gas tanks allowed in my garage :) glad you found that bug.