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Discussion Starter #1
Calling V8 mechs!

I've started hearing a top-end noise at cold-startup that I need diagnosed. I can best describe it as an series of irregular (between 1 per sec and 5 per sec) sharpish taps coming from under the front cam cover (top "rocker" cover not side belt-cover). The motor is a 3.2 V8.

It seems to come from near the end closest to the belts. It sometimes takes a second or 2 to start (from cold), and usually only persists for 10 - 15 secs, but has gone longer. During this time the motor is only running at < 1500rpm. By the time the car is on the road (30 secs) the noise is gone, never to reappear until cold. Even a restart at the end of the day after sitting all day gives no sound. Oil pressure is straight up in <1 sec. No other problems. Car is driven v.regularly (2 hrs per week min).

A mech I know has said sticking valves, needs an engine drop to rectify (as you can't access the front head in-situ due to bulkhead proximity.

Do I hear other opinions? The noise is quite irregular in rythym as in tap-tap-tapatapatap-tap with varying gaps between, is definitely metallic and sharp, but not overly "heavy". Considering the motor is doing 20 revs/sec (10 revs/sec camshaft) at 1200rpm, there is no way the tapping is that fast. Maybe every 5th cycle or so.

Is it possible for the buckets/tappets to be sticky in their bores until warmed? Shim problem? If sticky valves, how can the valve "stick" with such monstrous springs forcing it shut? Esp as the guide & stem wear with age (increasing the gap between)?

Any thoughts apprec. I'm loath to drop the engine without more advice.

Thanks.
 

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My guess is that it if it sounds like ball bearings in a blender... it might be the Air Conditioner compressor belt being loose. It is a common problem and goes away once the engine expands due to warming up. Of course feel free to have a mechanic verify.

The sound usually seems like it is coming from near the cam belts near the top of the engine. You could tighten the belt a small touch, i decided to remove the AC system in the car as it was fairly useless.
 

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Discussion Starter #4
Yep, seems like it was the accessory belts after all. I could have sworn it was a definite metal-on-metal tapping, so there you are.

Thanks for the tip - nipped-up the AC and Alt belts a touch (Water pump belt seemed on-spec), cleaned-up the belt & pulley faces as far as possible, and the noise has gone. I've just invested in a can of Belt Dressing which I'll apply tomorrow, hopefully that will put the *engine-out* problem to bed.
 

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belt

mu 89 was doing the same thing a while ago , it was the AC belt and the compressor bearings, i disconnected the compressor and belt, i also had an exhaust manifold leak that was making the same kind of sound, i thought it might be a valve out of adjustment as well, turns out it wasnt,i had the shop fix that as well on my major in 2010,Brett
 
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