Sacred Steel

Just pulled my tank because I'm replacing the sending unit and wanted to get a good look inside the tank. The inside of the tank looks good and the bladder looks to be in good shape and it doesn't leak. My question is, what's the life expectancy of these bladders and how reliable are they? Could I get a few more years out of it? I would rather not have to buy a new tank if these originals don't really have any issues.
Thanks

toobroketoretire

I have never heard of one leaking unless it got crunched.

Swiftrider08

Went thru the same thing on my 76 about 2 years ago. Inside of tank looked perfect and had not been leaking. Installed new sending unit and put the stock tank back in. No issues at all.

Sacred Steel

Cool, that's what I wanted to hear.
Thanks

76vette1

I ran into a strange problem where the gas level got low and the bladder inflated. I could not figure out why it did that since both sides of the bladder are vented. I ended up removing the bladder and running an unlined tank with no issues. The bladder is a safety item for rear end collisions, but could be removed if deterioration becomes a problem.

rebel542

I've got over 200K on a 79 with the original tank. No problem.

PMWARD

Chiming in on an older post, new member. I have run out of gas 3 times and at the most only been able to get 6 gallons of gas in the tank. I have read in other forums that GM knew this was an issue on the 75 - 77 units, and it has to do with the vent from the space between the bladder and the tank being plugged or the vent line to the emissions canister being crimped, cracked, or disconnected. I will be checking all of those easier things first but was wondering if anyone knew ... A) once a blockage issue is corrected will the bladder will go back into place, B) Is it in anyway possible to get to the vent (part of the filler neck) without dropping the tank?

revitup

The bladder will disbond from the tank and partially collapse inward, preventing the tank from being filled to capacity. Once that happens the only thing is to replace the tank.

PMWARD

Next questions, if the bladder is bonded to the inside of the tank why would there need to be a vent of the space between the bladder and the tank?, and other posts I have read said that the bladder can be removed if the neck/gasket area of the bladder is retained to seal the filler neck, any reason why I would not want to just remove the bladder. Every post I've seen state that the tank is super clean once the bladder is removed.

PMWARD

SO i started with the simplest of things, disconnected the vacuum feed from the carb to the charcoal canister, there was vacuum. I plugged the line back in and disconnected the canister line to the hard line that runs back to the tank - NO vacuum. Suspecting that the charcoal canister was plugged I connected the vacuum line from the cab directly to the hard line running back to the tank. After a few seconds I herd a THUMP sound and when I checked the tank it appeared as thought the bladder was sucked back into place! I replaced the charcoal canister with a OEM stock replacement (AC Delco - $50) and went to fill up. I noticed immediately that my gauge was reading correctly (near empty) and I was able to pump 14.5 gal. of gas into the tank. I watched the gauge rise as I pumped the gas in. I am also now able to see the gas in the tank (the bladder is no longer visible) and the gauge is working correctly. After some addition reading I learned the bladder is there to keep gas in the tank in the event of a rear end collision, and as such is likely NOT bonded to the inside of the tank so it can separate from the tank if it is crumpled in an accident and prevent leakage. I also found a few articles describing replacing the tank, where removing the bladder from the old tank and installing it in the new one is described. jury is not out yet of course but in the trips I've taken so far the gauge is correct AND i've noticed that when cruising the engine is running much smoother. Previously when cruising it would stutter a bit when not under load which made no sense to me. I believe with the canister plugged, bladder collapsed, and the gas cap closed, the tank was "vapor locked" and the fuel pump was struggling to pull gas from the tank. Now that the canister is venting properly (in both direction) fuel supply is flowing much smoother and the bladder is back where it should be ... and best of all I did not have to drop the tank! I will update this post if the situation changes.