Nick Woods Posted July 29, 2002 Share Posted July 29, 2002 Some of mine rattle from time to time, I'm fairly sure its tappets because its linked to the engine speed and seems louder at some times than others although I cant say I've noticed a definite pattern to it. Assuming it is the tappets can anyone explain why they rattle ? Is there any chance of long-term damage to the engine if they arent fixed ? Is there anything else that could cause this kind of noise ? the oil pressure is around 4 bar all of the time and the engine appears to run very well other than being a little bit tappety. Nick P8MRA - The green one with red wings Link to comment Share on other sites More sharing options...
Graham Sewell Posted July 29, 2002 Share Posted July 29, 2002 If the oil pressure is OK, then it would have to be the grade of oil - possibly too 'quick' (aka thin). But I'm sure that Roger or Oilyhands will be along in a minute to correct me! Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
Nick Woods Posted July 29, 2002 Author Share Posted July 29, 2002 Thanks Graham, but I've just changed the oil using Comma SynerG as before and as per the Caterham's rcommendations (1996 K-series supersport) and it made no difference. I'm more curious about why they rattle in the first place than the actual cure although I'd obviously be pleased with a cheap and permanent fix ! Nick P8MRA - The green one with red wings Link to comment Share on other sites More sharing options...
Ted_7 Posted July 29, 2002 Share Posted July 29, 2002 What's a "tappett" ??? Is it a valve or what ? Damn, my technical English is even worse than my usual English Cause I have something rattling too on my car, but it's in relation with the distribution belt. Se7enly, Ted_7 Link to comment Share on other sites More sharing options...
oilyhands Posted July 29, 2002 Share Posted July 29, 2002 There are a number of things can make them rattle, but the most common cause is aeration of the oil. A hydraulic follower relies on the contents of the hydraulic valve in its centre being incompressible in order to lift the valve, if the contents are pure oil then this will be so and everything will work as planned, if the oil is aerated then the minute air bubbles in the oil will collapse when the cam starts to lift the follower and the resulting clearance will be taken up like a hammer blow giving the characteristic tap/rattle. The hydraulic valves themselves can sometimes stick or jam with a similar affect. Excessive lift, too rapid valve acceleration or too little latent time to replenish can also cause hydraulic followers to collapse and exhibit the death rattle. Oily Link to comment Share on other sites More sharing options...
Nick Woods Posted July 29, 2002 Author Share Posted July 29, 2002 Thanks Oily - mine seem to do it all the time so does this mean there's no way to get the air out and is there any cure other than replacement ? Nick P8MRA - The green one with red wings Edited by - Nick Woods on 29 Jul 2002 15:12:40 Link to comment Share on other sites More sharing options...
scooby dooby doo Posted July 29, 2002 Share Posted July 29, 2002 the tappet is the thing that sits between the camshaft and the valve. On the K series its a cylinder about an inch diameter and an inch high that is basically hollow. on the bottom you can push it in a bit and it will spring out again. in use this quickly fills it up with oil (theres a valve in there to stop the oil coming back out) and it becomes effectively solid. Hydraulic tappet means just this - it uses oil to make it solid as oilyhands says. Thise means that as the engine wears in a 200,000 mile metro the tappets keep taking up the gap by taking in more oil. The problem is that high revs or agressive cams are a bit much for the mechanism and sometimes they stick - one of mine died at about 30,000 miles. Dave Hooper - dmch2@lineone.net Link to comment Share on other sites More sharing options...
Ted_7 Posted July 29, 2002 Share Posted July 29, 2002 Thnks hoopy I feel less idiot now Se7enly, Ted_7 Link to comment Share on other sites More sharing options...
scooby dooby doo Posted July 29, 2002 Share Posted July 29, 2002 i used to carry the knackered one in my bag to use as a paper weight at work.... Dave Hooper - dmch2@lineone.net Link to comment Share on other sites More sharing options...
oilyhands Posted July 29, 2002 Share Posted July 29, 2002 If the cause is a *sticking* follower then a quick strip down and clean / lap of the hydraulic valve usually fixes it, failing that I have a box of about 50 new followers here at a reasonable rate each. If the cause is oil aeration then oil surge is the pre-cursor to this, minimisng oil-surge will minimise the risk of oil aeration. Oily Link to comment Share on other sites More sharing options...
dogvet Posted July 29, 2002 Share Posted July 29, 2002 it has been seen quite a lot in the k series Academy cars, as these run standard Ks with the hydraulic tappets. As far as I am aware they have no problems despite the tapping sounds. It is not that easy to find the tappet causing the trouble, so replacing the lot is probably the easiest way, albeit it can obviously happen again with the new set. I ignore the noise on one of mine now and after a couple of miles with the engine oil up to temp is stops anyway. Link to comment Share on other sites More sharing options...
scooby dooby doo Posted July 29, 2002 Share Posted July 29, 2002 when mine went i had it replaced. by the time its come to bit the 15 quid for a new tappet is fairly minimal. Although I'll be going to solid tappets over the winter so that should remove the problem! Dave Hooper - dmch2@lineone.net Link to comment Share on other sites More sharing options...
oilyhands Posted July 30, 2002 Share Posted July 30, 2002 Hoopy - £15? I have new ones here at £5 a follower.. and they only take 10 seconds to get apart.. Oily Link to comment Share on other sites More sharing options...
Nick Woods Posted July 30, 2002 Author Share Posted July 30, 2002 Thanks everyone. If I've understood this correctly its usually caused by not enough oil getting into the tappets because either they have tiny air bubbles in them, or because they are gummed up so fresh oil cant get through the valve, or because they are worn and the oil can escape. Is this correct 🤔 If I strip the top-end down how can I tell which ones are worn - is it obvious just by looking at them or do I need special tools to tell ? Other than a torque wrench and a socket set do I need any special tools to get it all to bits and reassemble it ? Would either running engine flush through or removing them and cleaning them up with a solvent (petrol ?) help. Engine flush would be the obvious first choice but I'm a little concerned about not getting it all out of the engine afterwards, I assume that changing the foam baffle in the sump would be a must once its soaked in flusher. Nick P8MRA - The green one with red wings Link to comment Share on other sites More sharing options...
scooby dooby doo Posted July 30, 2002 Share Posted July 30, 2002 i wimped out and got ratrace to do the whole job. I suspect thats the rover + caterham's obscene markup price whereas you are at the cheap source plus special oilyhands discount rate. I did replace the head gasket on my car once with only mr haynes for company - i'm not THAT useless. honest! hang on! why do you mention taking them apart? ah! is it 5 quid for a new set of innard for one? the 15 quid got a whole new one. HOOPY Link to comment Share on other sites More sharing options...
oilyhands Posted July 30, 2002 Share Posted July 30, 2002 It's £5 for a whole new one.. If you are not sure which follower is ailing then it's best to strip and clean them all, any sticking ones will be obvious. When the internal valve is apart the one way ball can be checked and cleaned and the internal spring can be checked and the valve checked for free movement. Quite often a clean and lap is enough to get them operating efficiently but if anything is broken the the follower will need replacement. Oily Link to comment Share on other sites More sharing options...
scooby dooby doo Posted July 30, 2002 Share Posted July 30, 2002 ok - rub it in! I got ripped off.... HOOPY Link to comment Share on other sites More sharing options...
Nick Woods Posted July 30, 2002 Author Share Posted July 30, 2002 Without wishing to re-open the old engine flush debate, would using Wynns (or similar) get the old oil out of the tappets, clean up their little valves and then let clean and unaerated oil back in ? This is assuming that air is the problem and that the tappets arent knackered to start with. Or is it just going to cause more problems long-term because the flusher cant be got completely out of the engine ? (its not a VVC). I too am a bit of a coward with jobs like this so if there is an easy try-it-and-see fix I'm all for giving it a go. Nick P8MRA - The green one with red wings Link to comment Share on other sites More sharing options...
scooby dooby doo Posted July 30, 2002 Share Posted July 30, 2002 I'm going to say probably not as the tappet may actually be knackered as the spring inside is broken or its too worn inside etc. Now I'm going to wait for oilyhands to correct me! HOOPY Link to comment Share on other sites More sharing options...
Peter Carmichael Posted July 30, 2002 Share Posted July 30, 2002 If air gets into the hydraulic shims, the follower gap is not maintained and the followers miss the take up ramp and instead get a hammer blow from the cam profile. This hammer blow can catch the hydraulic shim slightly off-centre and cause it to wedge in position, or it can move the travel to a region where varnish deposits may have built up causing it to stick. Flush feels like it would be a bit too passive and hopeful a mechanism to get this sorted - unjustified reasoning - because the bit that is sticking is now shrouded by the outside of the telescopic shim and the area is mostly lubricated by splash. It may be worth it from a nothing ventured, nothing gained point of view. *thumbup*253 bhp, up and running Link to comment Share on other sites More sharing options...
Slarty Blat Fast Posted July 30, 2002 Share Posted July 30, 2002 To an untrained ear is there any chance of confusing tappet noise with injector noise? Absolutely no hitchhikers Link to comment Share on other sites More sharing options...
Nick Woods Posted July 31, 2002 Author Share Posted July 31, 2002 Thanks Hoopy & Peter. I might try some flush the next time I change the oil just to see if it helps although from what you've both said I suspect it wont because it cant easily find its way into the tappet. Nick P8MRA - The green one with red wings Link to comment Share on other sites More sharing options...
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