Noises noises noises

Hi Guys, Not been around on the forum for a little while as I have been very busy with other things! Unfortunately my 996 has picked up a gremlin over the past few months which I have been trying to diagnose and it's annoying me. Most usual input will say get it to an indi or hartech etc etc, I'm not really after comments like that, just useful ones please . Anyway I thought I would share with you guys (posting anywhere else will just have paranoid people shouting and crying about getting it trailered lol, as they do with any little noise). I have it booked in for a service at Northway on 5th Oct anyway, and they will be taking a looksie for me to give their opinion on it. Anyway on to my issue for a change - No noise on startup - No smoke ever regardless of how long I sit the car for - No oil use - No major oil leaks (slighlty damp on n/s cam chain tensioner bolt but no leak, nothing to worry about) - No engine noise while cold - No engine noise under load or when running - Pressure fine at idle and revs - No missfires etc etc etc, all runs smooth, diagnostics show everything fine, no error codes, everything running under normal constraints and normal readings, drives and runs smooth as it should. So on to the gremlin, when warmed up, on tickover, a hollow metalic clank. This seems rythmic and in time with the crank per one rotation. No loss of compression anywhere, spark plugs tight and ok, running ok, timing ok. If I load the engine bye bye noise, so air con on, it quitens and can vanish, slight touch of accelerator it goes (listening to the engine with someone else reving it doesn't seem to increase with revs at all, it just goes). To check for usual knocking noises, handbrake on, in first load the engine heavily with foot on the brake until it pretty much stalls - no noise. Clutch in and out does not seem to affect the noise. Any type of acceleration the noise goes away, loading the engine heavily in a high gear full throttle at low speed and rpm does not produce a noise, there is no noise at all when actually driving at any rpm or any condition. To cut a long story short, the noise occurs only at tickover, and only at full running temp (the caveat to this is after a good thrash down the dual carriageway the noise may not even manifest itself at all, even at tickover). So, I've listened all over the engine with a stethescope, and it sounds as though it is on the drive train, I can hear the chain going round and a slight clonk inside near the gear per one rotation. It doesn't seem to be in the bottom end or on any one cylinder or bank at the bottom end - it's pretty quiet there tbh, it's not near the ims bearing, nor the gear box, and it's not in the top end either. It's just resonating somewhere around the block and I can make it out along with the chain going round. I thought it could be a pulley at first, it had a new water pump and some other bits last year - could be a faulty one I suppose. It doesn't sound like piston slap, it doesn't sound like a bearing though, it doesn't sound anything like tappets. So I am puzzled. I dropped the oil - no metal, changed the filter - no metal, clean as a whistle from my last change. So other than the strange gremlin it pulls hard and runs as intended with no issues at all. I've not let it bother me tbh, as it still runs fine, and I've continued to use it, from the checks I have done there's little else I can do at this stage. I just posted up to see if anyone has heard of anything similar. Baz said on occasion he has had 3.4's in where they have stripped the motor, rebuilt and replaced and the noise has still been there. After analasys it's been something to do with the timing chain, and slight lash per rotation due to the design of the supply of oil and some people may just have to live with it. It could I suppose be a noisey IMS bearing, but it's really not coming from that location unless the sound is being thrown. In fairness, it may have been there for longer, I really don't know, as I don't leave the car on tickover after running and when I get out when it's hot - I turn it off then get out! It was only when I put the car in the garage a few months back I left it running as I moved a few bits around in the garage and noticed it. Anyhoo, it's in to northway soon for the 12k service, and I will let you know what they come up with if anything. But if it can't be diagnosed and a strip is the answer to poke around inside, I've already decided that I think it's a little pointless tbh, as I said, it's running perfect, and if the noise starts to occur straight from cold, when running or under load then I will start to get worried! Anyway, hope you are all doing well and your motors are going good, I will keep you posted! Cheers

Well, I just got home from Northway who serviced, inspected the car and gave the old girl a clean bill of health [ ] They've heard the same noise before on 3.4's, a metalic tapping / clunk eminating from the oil pump and Cylinder no 4 area. An oil inspection was done and it was clear - no debris or metal present. There is no oil being burnt, and no soot coming from bank 2 (where the noise is coming from). I had a nice long chat to the chap who was servicing and checking out the car, he said he wouldn't strip the engine to inspect as it wasn't worth it (because oil pressure is good, no debris or burning of oil, good compression and perfect running other than the noise at idle intermitently when warm). He also said they have had several motors in with the same noise in the same area, one particular customer had the same noise in that area three years ago, and has still been driving and having it serviced there and it has not changed. They also road tested to check for any other strange noises or related issues but reported nothing and said it was all good (I'm sure I would have noticed by now if different as well). It also seems that Hartech have experienced this issue as well from talking to Grant about it. All in all I was impressed with Northway, very genuine guys who don't mind you poking around the car with them in the workshop and having a good chat about your motor - I shall be going back again. When I asked what oil they put in it they recomended 10w40 for older higher mileage engines by the way, which I tend to agree with. The car flew there and back perfectly as usual, so all in all a happy bunny! Cheers,

P.S. the thought is that as the engines wear and some at different rates the whole of the running gear can become a little less 'taut' of course than from new. This will allow some play in components when there is no load on them nor the engine as a whole, this includes when in gear, or out of gear and slightly reving. It can manifest as an somewhat anoying noise at tickover if you listen for it outside near the rear off-side wheel, although does not constitue a serious fault that requires rectifying unless combined with other issues (such as burning of oil, contaminents in oil etc). The noise is usually seen/heard towards the end of the crank towards the rear pulley and nearer to the oil pump on bank no2 side, and can be caused by the chain and/or slight play in components in that area. Therefore the general advise is to keep calm and carry on, unless there are other symptoms and faults that require attention. Just thought I would share that, but of course, if ever in doubt get it checked over