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Old 10-12-2010, 04:44 PM   #1
TimQ
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Join Date: Feb 2010
Location: Bellefonte, PA
Posts: 81
Question What's this noise(w/audio)? Is engine about to die or might this rubber thing be it?

I thought I was making some progress with my 86 c-10 (86 4.3 v6 automatic with 89k original miles). The engine has never run better, started sounding good at idle after I fixed a vacuum leak, the odd knock it had went away after running some seafoam through and changing the oil a few times, the big puff of smoke it gave off on start up went away, and I even tracked down the oil leak from a bad seal on the passenger valve cover. For a few days, all was good. Then, of course, a new noise cropped up that is way different than anything I've ever heard before. I figured I'd record it and see what folks thought.


When I poke around with a piece of hose to my ear, it's loudest up against the oil pan. Some other symptoms

- It's not there on startup until I blip the throttle and get it down to low idle.
- If I give it a little gas (like in the audio) the noise goes away.
- It's not there when driving until I get to really low speed or idle at a light. In fact, the truck runs fantastic at speed.
- It seems to be worse in reverse...but goes away as soon as I give it gas
- oil pressure is good...40+ psi.

I found another thread where someone had a similar description and it turned out the exhaust pipe came loose from the headers. I checked and that's not the case for me but it does sound like a few big hollow pieces of metal clanking against each other rather than something from in the engine (or perhaps thats more a hope on my part). It would just seem that if it were in the engine, it would get worse with speed/RPMs.

To add to the mystery, pictured below is a piece of rubber I found in the driveway the other day. It could be from the truck or from somewhere else. Not really sure. Might it be some sort of pad from in a mount or something that would keep two pieces of metal from rattling?

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So what do you think? Is the engine about to eat itself? Is this rubber thing to blame? Something else?


Thanks!

Last edited by TimQ; 10-12-2010 at 04:47 PM.
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