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GTV6 Gas Tank Noise

3775 Views 10 Replies 5 Participants Last post by  fast goat
Recently the gas tank on my GTV6 has started to make a noise when I shut the engine off after driving the car. The sound is like a piece of metal that flexes back to it's orignal shape from a distorted shape. It's almost like there's a pressure buildup that finally releases after the car is turned off. Has anyone had a similar problem or any ideas on what's causing this???
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After you shut off engine, what happens if you open the gas cap?
I can hear the pressure releasing, but still get a bang from the gas tank.
I've also noticed that the bang I get from the tank is louder when there is less gas in the tank. With a full tank the sound is more muted.
tank over pressurisation. empty tank, remove vent valves, and clean
Thanks for your feedback, will let you know the results when I'm able to clean the valves.
I have the same on mine..... Where is the ventilation placed?
Group 4

This .pdf of Group 4 should help. On my 1982 I don't have the canister (#4).

Check valve is (#9) located under rear deck lid cover behind and above rear seats.

Problems usually occur when oily residue accumulates in areas 3, 4, and 6; occasionally blocked check valve.

Greg Gordon has an outstanding a tech bulletin on this:

Here are 1987 Tech notes from the late great Fred Di Matteo (Velocissima-AONE)

And for the 1983 and before models; EMM.pdf attached, section D-21 from Group 4, probably best shows the check valve in question #3 (notice no charcoal canaster; in 1983 and before from oil separator to firewall then hardline (#2 - on vehicle interior) to rear of alfetta where check valve placed in line prior to vent line and expansion tank)


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Thanks Balocco211
Clogged vent valves was my problem. After cleaning no further problem
Missing Vent Valve

My car does not have a vent valve (removed by PO?).
Does anyone know of a suitable replacement?
Thanks for your help..
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