As the title suggests, its on my old mans "project" he has a 76/77 F100 Ute. It is running a Chev 6.8L? Diesel.

Anyway, he lent it to one of the nuptys at his work the other day and it has come back and the right door speaker (some crappy make) is playing engine noise. This is with the stereo on or off. Also when you are about to start it and the glow plug timer is on it lets off this big fuck off almighty squeal through the speaker which stops the second the glow plug timer turns off. I pulled the door trim off and checked the connections to the speaker, the connections are soldered on really well. I checked as much of the wiring as possible and it all looks fine. As I say this is just after one of the goons drove it. I asked the dude what he did when he drove it and of course he says "nothing". Does anybody have any ideas?

Cheers..