V8david Posted May 6, 2009 Share Posted May 6, 2009 Hi all. Got a loud sort of tapping noise that's started and got worse of late. It's worst when the engine is cold and accelerating, usually starts around 2000rpm. It gets louder as I accelerate, stops when I ease off and stays away unless I put the gas back on hard again. Much better once it's warmed up but still comes back slightly under hard acceleraion. Definitely coming from one cylinder area. Is it a tappet? Worth doing an engine flush/oil change? 3.5 V8 Efi. Cheers Quote Link to comment Share on other sites More sharing options...
Quagmire Posted May 6, 2009 Share Posted May 6, 2009 It's worst when the engine is cold and accelerating, usually starts around 2000rpm. It gets louder as I accelerate, stops when I ease off and stays away unless I put the gas back on hard again. Much better once it's warmed up but still comes back slightly under hard acceleraion. Sure its not pinking/detonation? Changed the timing recently? Mine does this a little when on petrol if i'm not careful as i have mine advanced for LPG running. I have to drive around it (not through it). Quote Link to comment Share on other sites More sharing options...
DC_ Posted May 6, 2009 Share Posted May 6, 2009 Done anything recently with the manifolds? Could be a leaking gasket, sounds very similar to a tappet. Quote Link to comment Share on other sites More sharing options...
V8david Posted May 7, 2009 Author Share Posted May 7, 2009 Thanks for the replies guys. Yes, changed everything recently!! Had the heads off etc. New cam, lifters etc etc, as well as all gaskets. Definitely only coming from one cylinder, would pinking do that? When warmed up it gets much quieter and harder to hear, not at all unless I push really hard, which makes me think is it oil draining down over night stopping a lifter working? Or is it a tiny gap somewhere that closes up with heat? When you say manifolds DC, do you mean exhaust or inlet? Obviously I've had both off. I'll start by re-checking the timing. It's set off the timing marks on the crank pulley at the moment so could be way out. Should've found TDC properly when I had it all apart... Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 7, 2009 Share Posted May 7, 2009 I'd take a really close look at the manifold gaskets TBH, they blow for a past time. Quote Link to comment Share on other sites More sharing options...
Quagmire Posted May 7, 2009 Share Posted May 7, 2009 If its def only one cylinder then i would go with tappet or leaking exhaust fanimold. Can't hurt to doublecheck timing though just to be safe, if it is pinking you wanna put a stop to that ASAP. Quote Link to comment Share on other sites More sharing options...
DC_ Posted May 7, 2009 Share Posted May 7, 2009 David, yes as the lads say exhaust manifolds, sounds very similar to tappets. Are you on LPG or petrol? When it heats up if your on petrol, it's been suggested that the build up of carbon deposits may plug the leaking slightly and this is why maybe it's less noisy. Get it off, get some asembly paste on it with new gasket and hopefully that'll be it gone. Quote Link to comment Share on other sites More sharing options...
V8david Posted May 7, 2009 Author Share Posted May 7, 2009 Nice one. Cheers for the replies guys, i will investigate further! I'm on LPG. Only start it on petrol, runs a bit rough on it, really smooths out once the LPG kicks in. I assume the timing is advanced more for the LPG. Anyway, as I said, I will have a check over everything... Quote Link to comment Share on other sites More sharing options...
DC_ Posted May 8, 2009 Share Posted May 8, 2009 now i'm really going to follow this thread with detail. LPG will make your engine hotter when running. This will expand the cylinders more and will make the noise louder?? If you run it on petrol for a while, say about 25 mins or so, does the tapping go away? If you round around at 30mph does the tapping stay away? does the tapping return when you make the engine work harder say at 50-60mph? One theory might be that when on LPG the cylinders expand more but also as it burns cleaner, there's no deposits to "block" u the leaky gasket. So it it goes quieter on petrol this might be the case. Hope that helps David, Keep us informed. Quote Link to comment Share on other sites More sharing options...
V8david Posted May 9, 2009 Author Share Posted May 9, 2009 Well latest update. Tried her cold around the block today, just on petrol (not done that for a long time!) Anyway, same noise, same symptoms. Doesn't really matter what the speed is, it's when the engine's working hard. i.e accelerating hard uphill. This is what can bring the noise back slightly even when the engine is warm. I'll try to have a look at the timing tomorrow and report back. If that doesn't change anything then I'll look at gaskets. May even try a short film on my digital camera, see if I can't capture the noise for you to hear! Quote Link to comment Share on other sites More sharing options...
DC_ Posted May 9, 2009 Share Posted May 9, 2009 Is it like a kinda grinding metal to metal noise?? Can you hear it tapping when idle? Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted May 10, 2009 Share Posted May 10, 2009 This sounds very like when the injector seals went on my old Range Rover - sounded very like tappets or exhaust manifold, made it run rough under load and refused to play up when it wasn't, which made it a pig to track down. If it's that, best bet is to get a mate to rev the engine under load (wedge foot on brake, put it in drive and give it some welly - don't over do it, I doubt it's very good for the gearbox) while you stick your head under the bonnet and have a listen. Just make sure it's a mate you trust and stand at the side of the car not in front (or put it in reverse). Quote Link to comment Share on other sites More sharing options...
Coastcard Posted May 11, 2009 Share Posted May 11, 2009 I am also with Geoff above. I had this tapping/knocking noise under load (which I thought was a bearing going on my recently recon. engine!!) and rough running. Eventually fitted some reconditioned injectors (with new seals) and bingo all is well - amazing difference. Quote Link to comment Share on other sites More sharing options...
steve_d Posted May 11, 2009 Share Posted May 11, 2009 As this is on petrol or LPG it is not going to be the injectors. To me it really smacks of exhaust manifold to head so two things.... 1. Have you put an exhaust gasket on upside down or back to front? Both are possible and result in only about 2mm of gasket at the worst point. 2. Are you sure you properly tightened the bolts as some are a complete barsteward to get at and can be forgotten in the final tightening sequence. Steve Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted May 11, 2009 Share Posted May 11, 2009 As this is on petrol or LPG it is not going to be the injectors. Steve - injector seals, not the injectors themselves. If the o-ring seals go then air is sucked in round them regardless of which fuel you're running on, and makes a sound virtually indistinguishable from an exhaust manifold leak. Quote Link to comment Share on other sites More sharing options...
V8david Posted May 11, 2009 Author Share Posted May 11, 2009 Thanks for all the thoughts guys. Update as follows... Checked timing again and set it to 12 degrees BTDC. (been advised by many that the extra 4 degrees advance is ideal for LPG). Running much better now but still getting the noise. Pleased I finally got off my arse and sorted the timing... I'll start with the exhaust manifold first, at least I can narrow it down to one bank! Then on to injectors beyond that (good thought Geoff ) Not sure when I'll get round to it though. I know the exhaust manifold bolts you're talking about. The very back ones, especially nasty with the tubular manifolds. Much stripped knuckles, swearing and tool throwing happened when I was tightening them up! I'll update when I've had a look... Thanks again. Quote Link to comment Share on other sites More sharing options...
steve_d Posted May 11, 2009 Share Posted May 11, 2009 When referring to the injector seals are we talking about a seal that has failed and is sucking in air? If so then get a propane blow lamp and with the gas turned on but not lit play it around the injectors. If the engine speeds up then you have found your leak. All normal health and safety caveats apply. Steve Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted May 12, 2009 Share Posted May 12, 2009 I know the exhaust manifold bolts you're talking about. The very back ones, especially nasty with the tubular manifolds. Much stripped knuckles, swearing and tool throwing happened when I was tightening them up! They're much easier with a ratchet spanner....until it comes to taking the spanner off Doh!* When referring to the injector seals are we talking about a seal that has failed and is sucking in air?If so then get a propane blow lamp and with the gas turned on but not lit play it around the injectors. If the engine speeds up then you have found your leak. When I did that the results at idle weren't all that consistent, even though it turned out the seals on one injector had gone completely (as in they weren't there ). Sometimes there was a noticeable effect, sometimes there wasn't - I think part of the problem is that the draught from the fan blows most of the gas away. Incidentally, my problems were caused by not replacing the seals when the injectors were out - false economy, they cost pennys so now I would replace them as a matter of course no matter what condition they were in. * - yes, I really did do that Quote Link to comment Share on other sites More sharing options...
DC_ Posted May 12, 2009 Share Posted May 12, 2009 Just out of interest, how easy would it be to replace the seals and where would be a good source to get them? Quote Link to comment Share on other sites More sharing options...
V8david Posted May 12, 2009 Author Share Posted May 12, 2009 Hi DC I'd get them from... larger seal and... small seal They're really good I've found. Usually got a picture of stuff as well so you know what you're looking at. I know what you mean about the ratchet spanner Geoff, I've had a few stuck in various places on the engine! Thought does cross your mind to leave it there... Quote Link to comment Share on other sites More sharing options...
DC_ Posted May 13, 2009 Share Posted May 13, 2009 Cheers Easy enough job ?? Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted May 13, 2009 Share Posted May 13, 2009 I know what you mean about the ratchet spanner Geoff, I've had a few stuck in various places on the engine! Thought does cross your mind to leave it there... I did leave it there for about a week, then a particularly bloody minded friend managed to lever it off. Surprisingly didn't come to any harm from being attached to the exhaust manifold for several days of driving! Easy enough job ?? Pulling the injectors out from their sockets in the inlet manifold and fuel rail (if you change the seal there too) can be a bit of a swine - though if there are failed seals on some those will be easy - other than that it's a pretty straightforward job. You'll have to remove the plenum to get access, so make sure you've a bit of blue instant gasket around for refitting it. Quote Link to comment Share on other sites More sharing options...
DC_ Posted May 13, 2009 Share Posted May 13, 2009 Cheers Geoff, will bear that in mind if/when i do them at some stage. Quote Link to comment Share on other sites More sharing options...
V8david Posted May 19, 2009 Author Share Posted May 19, 2009 Cheers guys, tightened the exhaust manifold nuts, couple of them took a couple of turns, most were tight. Anyway, noise gone! Onto the next problem... Quote Link to comment Share on other sites More sharing options...
DC_ Posted May 20, 2009 Share Posted May 20, 2009 Nice one david, Quote Link to comment Share on other sites More sharing options...
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