I had my fuel tank replaced, and before I go back to the garage that installed it, I want to figure the problem out myself. While I'm driving, the tank maked a thump sound every now and the. It will also do it when I let it run and remove the gas cap. It has a vented cap on it now(could be faulty, so I tried a non-vented cap, and it still does it. The only other thing I can think of is there may be a problem with the vent under the tank.

89 Transam GTA, a few bolt ons

 

Are you going over bumps when this happens? Once, I had a piece of "anti-squeak material" (tar strip) slide out from under one of the mounting straps. The tank would thump every now and then because of that. It was an easy fix; loosen the mounting strap, slide the anti-squeak back under, tighten the strap. Maybe they left one out?

Either that, or maybe the shop didn't re-attach the right rear hanger for the exhaust system, and the intermediate pipe (between cat & muffler) could be resting on (and banging around on) the track bar brace suspension piece. The hanger should be on the I-pipe right before it curves into the muffler... it bolts to the upper rear passenger frame rail with two bolts.

Of course neither of those explains why the tank thumps when the car's not moving; but they're two quick things to check


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

I will check those things this weekend. I have to jack the rear end up anyway to replace the rear shock bushings because they squeak. I'll check the straps and the exhaust while I'm under there. The tank thumped when I took the cap off with the engine running, leading me to beleive it is due to a pressure increase/decrease inside. I put a non vented cap on, so I'll give it a couple of days to see if it does it. Thanks

89 Transam GTA, a few bolt ons

 

I know what your talking about.

My car could be sitting out front of the house for about 20minutes after being driven and it sounds like somebody comes up and kicks it! huh?

I replaced the pressure relief valve above the drivers LCA and havnt heard it since

BTW John Leinghenfelter told me to try that