Noise from gas tank (metal expansion)
2002 GMC 2500 SLE with extra large gas tank (46 gallon). Makes a banging sound a few minutes after stopping a vehicle and turning off engine. It used to rarely do it an now I hear the sound sometimes when driving down the road. I do have a locking gas cap. At least I think the sound is coming from the gas tank. However I could not rule out catalytic converter or muffler.
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4 Answers from these members:
I strange noise coming from the vehicle can really cause some concern and I will be happy to help. I am adding two links below that describe a similar question. I hope this helps while you wait for your expert response.
by Joseph Perez
Are you getting any check engine lights on dash?
If you still have the original gas cap swap it back out for a couple of days. There is a safety valve on the cap to prevent excessive vacuum, from the EVAP system, collapsing the tank. The exhaust would be more of a crackling sounds than a banging sound.
I don't have the original gas cap. Shortly after I put the tank on way back in 2003, I got a locking gas cap. The tank always made a sound usually after parking and stopping the engine, but it was barely noticeable. Now recently It does it going down the road. So I bought a non locking gas cap to test. I noticed a bang about every half mile driving around our little town. So, my next plan is to drive around a while without a gas cap on and see if the banging is around. I don't think I have exhaust problems, that was inspected recently. I still think I may not have the right gas cap. The tank is a Transfer Flow 46 gallon tank I had installed way back in 2003. It may be i still don't have the correct cap.
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