Annoying engine noise; cam? Valves? Gremlins? (video/audio link included)

[Daniel81DMC]

Had the issue for about a year, now - annoying engine noise. Sometimes it makes me think exhaust gaskets, sometimes I think valves, sometimes I swear the car is possessed by gremlins.

Only factors that I can think of to share that matter would be:

1. You don't hear it all the time.
2. The sound is almost exclusively heard and/or loudest after the engine is warm and has been running awhile.
3. I run 20/50 oil, the engine has 53,000 miles, and as far as I and my mechanic are aware, has no major problems (doesn't burn oil, doesn't stall, nothing).
4. The car runs just fine - accelerates well, doesn't miss, no problems I can detect.
5. Car had been running for about 20 minutes before video was taken, so it was warm. Car had a heating problem about a year ago, but ever since, has run very cool (had a problem with my fans, but fixed it), so the engine was not over-heating in this video or even close to it.

Any input welcome; I'm mechanically fairly sound in my knowledge of cars, but distinguishing various issues by ear alone isn't my strength - I don't have any true mechanical training.

Thanks for any input, gents. I think the noise is most noticeable around the 16 or 17 second mark, but the whole video is only about 30 seconds, so give 'er a go.

Video link: http://www.youtube.com/watch?v=pjGFrtZgReQ

[Spittybug]

It might be easier to diagnose if you shot it again and did indeed try to correlate where you were aiming when the sound was most pronounced.

I can hear what you mean at the 16 sec time period, it sounds "throatier, growly, frictiony". Not what I would associated with lifters. Maybe tension pulley bearings? A/C compressor clutch bearings? Alternator? If it is worse once warm, that would indicate to me that something has expanded and is now rubbing or grinding. I would expect engine internals to be noisier when cold before all the oil gets moving.

Just suggestions to look for.

[Daniel81DMC]

Thanks, I appreciate the suggestion - if it's any help, the noisier part was taken when I had the recorder beside the passenger-side bank of cylinders - that's part of the reason I assumed that it may be valves.

I can try re-shooting the vdeo, we'll see if it I have some more luck! It is rather interesting that it happens more when things warm up, usually (damned odd, in my mind, as you're right - you'd expect it to be the reverse.)

[David T]

Adjust the valves. If you still have the noise replace the exhaust manifold gaskets.
David Teitelbaum

[Daniel81DMC]

http://www.youtube.com/watch?v=eLz3kcQwsrA

NEW video - brighter, a bit longer.

Anyone able to guess more conclusively as to exhaust gaskets or valve job?

Thanks, David, by the way.

[DMCMW Dave]

If it is louder under load (put the car in gear or drag the clutch with the brakes on) OR louder cold and then tends to go away, it's the exhaust. If it is consistent regardless of load it's the valves.

[Daniel81DMC]

It's loudest when the car is warm - it's quietest (almost unnoticeable) when the engine is cool. Can't comment as to the 'under load' bit - when I'm driving forward (i.e. doing the speed limit down a road) I don't hear it at all - I don't know if that's simply because the sound is behind me and I'm moving forward, of it's simply quieting down when driving.

I'll be taking the car to my mechanic in a week, maybe he'll have a better idea, I just wanted to get a rough concept of what to tell him - sort of like a doctor, I know they aprpeciate it when I can come at them with a, "this is what needs fixing" ;)

[DMCMW Dave]

Is it a manual or automatic?

[Daniel81DMC]

Is it a manual or automatic?

Manual - but... it's definitely coming from the engine area. I've never heard of anything transmission-related making that kind of noise (but there's a first for everything, and DeLorean's are indeed 'special cases', hah!).

The second video that I shot there (the one where you can I actually see where I'm pointing the camera) is about as good a rendition of the issue as I can provide.

[DMCMW Dave]

I was asking because there are ways to put a load on it sitting still so you can hear the noise.

On an auto you simply have an assistant stand on the brake and press on the gas a bit at the same time (in Drive).

On a manual they will need to have the brake on and start engaging the clutch in first gear. Then you can stand behind the car and listen to the sound.

As I mentioned - if it gets louder at this point it's the gaskets.

[Daniel81DMC]

OK, thanks a lot Dave - gaskets or valves it is - my original guess was valves, so at least I'm in the area.

If anyone else wants to chime in, always appreciated!

[Daniel81DMC]

Just as a general note - got my car back from my mechanic today, and apparently the noise in the engine bay is... fairly normal. I suppose I've never really heard a PRV-6 before (well, one other, one time, so far), and it sounded fairly similar. For a relatively small block, the thing is just makes a fair bit of a racket, but I suppose that's old push-rod engines for you. Oddly enough, I never noticed it in my Corvette's, but perhaps I'm just growing more sensitive to the noise as I get old and cranky (I turned 30, today), and as there isn't much distance between the driver and the block (and not exactly a lot of sound insulation, either.

Bottom line? It could maybe use a valve adjustment, but it's not a hard knock or anything damaging - just a little annoying.

My thanks to those of you who lent an ear!