Need Help/Advice on 71 Eldorado

Started by Mike Shawgo #20545, January 29, 2007, 06:37:06 PM

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Mike Shawgo #20545

Hi everyone,

I am working on my recently-acquired 1971 Eldorado convertible, and have run into a couple of things that maybe some of you can help with.  Any advice is very much appreciated.

1.  I was jacking up the left rear with the tire jack to remove the left rear tire to take it in to get a slow leak fixed.  When the car was jacked up, I heard something dripping, and it was gas dripping out from the right front of the gas tank.  The tank is full of gas.  Is this something to be concerned about, or is there some type of overflow valve that by jacking up the car with the tank full, the gas was running out of?  I couldnt quite see where the gas was coming from--seemed to be from the top of the tank somewhere.

2.  I noticed a hole in the floorpan right over an area where the tailpipe runs.  The car has very little rust overall, but I know floorpans can be a problem in these 70s Eldo convertibles.  I hate to think of replacing floorpans, and dont even know how this would be done.  Can a floorpan hole be successfully patched or repaired?  Can I do anything to stop further deterioration of the floorpans?  I am going to have the exhaust replaced this spring, and since the hole is right over the exhaust, is patching or repairing the hole something a muffler shop could do while the exhaust pipe is removed?

Mike Shawgo

Bruce Reynolds # 18992

Gday Mike,

Firstly, congratulations on your purchase.

Now, I would be very wary of any petrol lealing from anywhere under the car.   As these vehicles run a sealed system, I dont believe there is any breather at the tank, like the cars of old, so I would be dropping the tank to investigate, and be prepared to fix.   It may just be a simple degrading of the fuel line hose, a leaking sender gasket, or a hole in the fuel line itself.

As far as the hole in the trunk, it is a relatively simple task for someone with the skills of panel replacement/bodyworks to cut out and weld in a home-made patch panel to fill in  the hole(s), but not a job I would be leaving to an exhaust shop to perform.   The completed job(s) have to be painted both sides, and an exhaust place wouldnt be set up for that sort of job.

No real need to go to the trouble of finding commercial patch panels for these areas.   But, make sure that any area that is cut out that has a fold or creasing, the replacement piece of sheeting is folded or bent to the same contortions as they were put there for a reason.

Plus, if you take out the fuel tank, it would be a good time to do the "Rust" replacement as you dont want the risk of any petrol fumes getting involved with oxy welding flame/Mig Welder sparking.

The Tassie Devil(le),
60 CDV.

TJ H 20664

For the fuel leak my bet/hope is the rubber lines.  There are 3 steel lines that come up in the pickup/sending unit in the center(ish)of the tank do a 90* bend and end about flush with the edge of the tank.  There is then about a foot of hose that connects this to the steel lines that run along the frame to the front of the car. The factory clamps are those spring ones that you can get off with a needle nose.  If someone put regular clamps on there with the tank down you will have to drop the tank to get them off.  Its kinda a pain on the tank side but it can be done.  Its much easier on a lift but I did it on jackstands.  IIRC the fuel line is 3/8" and the vent 5/16" and the return 1/4" but its been a while.  

While you are under there its a great time to check the steel brake and fuel lines on the drivers side, look real close where the clips are that hold it to the frame, for some reason those rust out worse than anywhere else on the car.  Have a look at the rubber brake lines too, back then 10 years was about the lifespan of those rubber parts.  On my 78 cdv the brake and fuel lines were rusted out at every clip, I started out replacing the brake line in one spot after it blew then noticed the fuel leak, long story short after several repairs and trips to the store we ended up with new steel brake lines and new steel brake line for the fuel line from the firewall to the back.

Enjoy the car, pick up a genuine GM shop manual if you plan to do any repairs yourself.  The genuine manual will save you a lot of time and trouble, dont wast your money on the generic manuals they cover too many years.

StPaul/Mpls MN USA
73 Eldo converts
75 Eldo
78 CDV

Mike Shawgo #20545


I feel dumb, I DO have a shop manual, just never thought to pick it up to look up the fuel tank.  I see there are several hoses coming out at the top--vent hoses, etc.  Im sure it must have tilted the gas up to those, and the hoses must be leaking around the connectors, or the hoses are bad themselves.  Probably all need to be replaced.

Thanks all for your replies!

--Mike Shawgo #20545

Joe G

This is an often overlooked problem, and it should be fixed IMMEDIATLY! The hoses get brittle and clips rust/rot, because the heat from the nearby exhaust pipe helps that process. Then the leaking gas and the hot pipe get together.....and you have a fire! The 71-78 Eldorados are very prone to this.

Mike Shawgo


Thanks, sounds like excellent advice, and I plan do take it!

--Mike Shawgo