Unknown noise.

[Frosty]

So havoc, have you had a chance to check for exhaust leak(s) yet?

[havoc1482]

So havoc, have you had a chance to check for exhaust leak(s) yet?

Unfortunately no.

Vapor lock is the new thing. Exhaust leaks are so last month.

[Frosty]

How are you getting vapor lock? That means the gas line is close to a heat source and it is vaporizing in the line. So how does that happen and why would it show up now after all these years? Unless the fuel pump diaphragm is getting old and tired and not producing enough pressure.

Assuming that is the problem, what are you doing to fix it?

[havoc1482]

How are you getting vapor lock? That means the gas line is close to a heat source and it is vaporizing in the line. So how does that happen and why would it show up now after all these years? Unless the fuel pump diaphragm is getting old and tired and not producing enough pressure.

Assuming that is the problem, what are you doing to fix it?

I got my lines and tank replaced about 2 weeks ago. The gas cap isn't venting properly and its causing a vacuum to form in the tank. So its starving the pump for fuel. I didn't have the issue before because there was a rusty hole on the neck of the filler so it couldn't built a negative pressure. The gas cap was painted over when the car was taken out of the junkyard to be given some love, so i think the vent is gunked up or something.

My plan to fix is to get a new gas cap or try to get it to vent properly. For now I just leave the cap just shy of the first click so there it vents. I'm not concerned about it coming loose because it is behind the license plate, so even if it was to somehow come all the way undone it cannot physically come off. And the neck has a spring loaded stopper so gas can't get accidentally splash out.

[Frosty]

I got my lines and tank replaced about 2 weeks ago. The gas cap isn't venting properly and its causing a vacuum to form in the tank. So its starving the pump for fuel. I didn't have the issue before because there was a rusty hole on the neck of the filler so it couldn't built a negative pressure. The gas cap was painted over when the car was taken out of the junkyard to be given some love, so i think the vent is gunked up or something.

My plan to fix is to get a new gas cap or try to get it to vent properly. For now I just leave the cap just shy of the first click so there it vents. I'm not concerned about it coming loose because it is behind the license plate, so even if it was to somehow come all the way undone it cannot physically come off. And the neck has a spring loaded stopper so gas can't get accidentally splash out.

OK, new re-pop caps are plentiful. So that solves that mystery. I would still consider replacing or rebuilding the fuel pump just for insurance purposes. It is still an old piece and it probably wouldn't hurt.

Now all that said, have we figured out what the unknown noise that started this whole thread yet? If not, what are your next steps in that direction?