Tapping/tappet noise when driven hard

After lots of great advice from this forum, I recently bought my first 911 - a facelift C4. Love the car, but I recently noticed that it makes a fairly loud tapping noise when you drive it hard(ish) (take it to about 6K RPM 5-6 times in a row when the car is full warmed up). The problem goes away if you drive sensible for about 10 minutes, or if you turn the car off for about 2 hours and then turn back on. It sounds like a tappet/lifter (metallic tap of about 4 taps per second at idle from left bank), but I thought tappet problems would be present all the time, not just when driven hard??? An independent Porsche specialist just replaced a chain tensioner, but the problem is still there. Has anybody had a similar problem or have any ideas?

Hi, Check the basics first - oil level , go off the dip stick rather than dash. Could be as simple as that or too thin an oil used, otherwise ease of the driving hard and take it back to a good indy for further advice, could relate to a sticky / worn component Get some pics up of your new purchase :thumbs:

If the porsche specialist, after having analysed the fault first hand, got it wrong, I guess we are unlikely to fix it unseen. But mine does that too, it doesnt bother me. I think mine is a poor tappet that at low oil pressure ( idle and hot) doesnt pump up enough, hence a noise. Mine disappears at at 1200 revs, so again I'm not too worried.

Sounds like a bucket tappet failing, maybe blocked but the only way to sort it is take out, compress and re-install but because it is a big job they may aswel be replaced. On the initial stages of failure they are noisey for upto 20 seconds from a cold start but will clear. If noisey when warm then I'd advise no hard thrash, it will be hammering away at the camshaft at several times per second eventually flattening out the egg shape of the lobe, this means you will lose the lift on that particular valve. I feel the Porsche 996 NA has enough potential big issues as it is, don't add to it by thashing the engine when tollerances are out. Get it seen to ASAP.

I get a tappet noise when starting from cold (up to 20 seconds) I'd say. It does go away though & doesn't re-occur at any point when the engine is warm. Does this mean that I have a problem that needs rectifying? Does anyone know the cost of this (approx)? Am I doing any harm in running the car like this? Thanks in advance :wink:

You'll find with a quick blip on the acc. pedal the tapping will clear due to the oil pressure increase, this is better for the camshaft than leaving it ticking over & tapping for 15 secs+ It is the early stages of failure, Grant @ Hartech or Richard H on here would be best to ask for approximate costing.

Thanks Lloyd, I'll try that. When you say failure, is this failure in any way catastrophic or is it just the tappet failing and will therefore make a tapping noise until rectified? Does this have any other knock on effects :?: Is it also worth noting that the car isn't a daily drive so doesn't get run everyday. Could this have any bearing on the tapping? :?: Grant or Richard - Any idea on approx prices for this? :thumb: Thanks :thumbs:

Hi, You've not said what mileage is on the car or if it's a 3.4 / 3.6. It's always better to try and get any potenial issues fixed in the early stages, and it will work out considerably cheaper. I would budget between 3-5K for engine out, strip down, repair and any upgrades etc. As said above, ease off thrashing it and get onto hartech straight away speak with Baz http://www.hartech.org/contact.html otherwise if it's under any warranty get it into your local OPC good luck! brumbrum

p.s Grant is from Hartech too

It will, if it starts happening when warm / hot as it will damage the camshaft. Then if totally ignored it could destroy the engine but it would be VERY loud and clattery before it got that far.

Sorry, are you referring to me (the hi-jacker :O) of this thread or the original poster jfishwick My car is 3.4 Are we seriously saying that because one of the tappets make a slight noise from cold start, I need to have the engine out & rebuilt to rectify? The noise only lasts about 15-20 seconds as specified and then goes away. The car runs perfect in every other way. Is this knocking tappet in any way catastrophic or is it just the tappet failing and will therefore make a tapping noise until rectified? Does or could this have any other knock on effects? Am I doing any harm in running the car like this? :? :?: Cheers

I don't want to worry you - but usually a tappet is not noisy once it has filled up and so sometimes (not always) the problem relates to a crankshaft bearing wearing out. They can fail and give your symptoms but I am particularly concerned because of the noise increasing under load which tappets don't usually do but crankshaft bearings do. It is however relativley easy to check by removing the oil filter and inspecting it for particles of metal or bronze or gold coloured pieces. Look inside the folds on the filter by prising the vanes apart. If you see anything get it somewhere to fix it before the crankshaft is damaged beyond use (they are very expensive to replace). Sometimes this is caused by the silicon crankcase sealant that squeezed out during engine assembly and formed a bead on the inside of an oil gallery - finally falling off and blocking or partially blocking an oil passageway. We have even seen (and photographed) an oil pick up where it was totally blocked by such sealant (and of course the crank was beyond repair). It is also possible that an oil filter that was not changed when it should have been - has become blocked reducing the oil flow to the engine. As you probably know we rebuild a lot of these engines and although we only ever had one with a broken valve spring before - this month we have had three and in each case the valve has dropped inside and wrecked everything (piston, cylinder and head etc). The one we originally found was brought in in time to avoid the resulting damage and that one had a ticking noise like a tappet - the recent ones were not so lucky and came in already damaged. Your problem probably is not due to any of the above failures (and I hope it is not) but I do think it is worth having the oil filter checked for particles and replaced at the same time and follow that (if it is OK) with a check of the tappets and valve springs. Baz

Hi Baz, Mine doesn't increase under load. No noise from mine at normal running temp. at any revs. Mine simply taps from cold (not a daily driver) for a few seconds. As stated, the car isn't a daily drive so doesn't get run everyday. Could this have any bearing on the tapping (Until oil is circulated)?

adamw my reply was a response to the first description. Yours sounds like a classic tired tappet. When the engine stops there are always a few valves left sticking out in a cylinder and therefore under the valve spring load trying to shut them. If they are getting tired or the tappet housing is getting worn or the oil is too thin for the age of the car then that spring load squeezes some oil out while it is still hot. When you start up the oil is now thick (as it is cool) and cannot get into the tappet through the small hole quickly enough to fill it up until it has warmed up a bit and gone thinner - after which it is OK. This usually doesn't happen every start up as the engine should stop in different places randomly but if the cylinders are getting distorted and there is more compression on one particular cylinder - it can more often than not stop in the same place. Doesn't sound like anything to worry about. Baz

Thanks for getting back to me Baz, Now you come to mention it I don't think it does happen every time I start the car. In your opinion, should I be looking to get this rectified or is this "tired tappet" just a characteristic of a 996 of this age (9 years)?