Ahh, the ole tappet topic. Again!
If only the bloody forum wouldn't keep going titsup we could have a good point of reference for this one, as it is though I'll go through it again. this time though I'll save the explanation as a text file so I don't have to type it ever again! (Not your fault Willy, we really should have a FAQ!)
The noise is caused by a buildup of crud inside the hydraulic tappets (or lifters) that are driven by the camshafts and act on the valves. The design and it's flaws are common to most Mitsubishi engines. By sticking and not fully filling with oil they make the characteristic ticking sound you describe. Most if not all Evos are thus afflicted with 'the tickies' as my girlfriend calls them.
Is it damaging my engine? , I hear you ask - the answer is no, not really. Although the problem can affect engines as young as 5000 miles and can be heard on engines that have done more than 100000 miles there is no indication of long term damage. The worst that can happen is mushrooming of the valve stem, but according to our learn'd friends at
dsm.org this is only likely to happen if the engine is subject to long periods of extreme use e.g. frequent track use or rallying. Even then it is incremental damage, you'd have to drive like this for a while before any degradation would be noticed.
What can I do about them then? is obviously the next thing on your mind. Well, you can change them, clean them or just try and live with it! I'll go through your options:
1) Change the tappets - Identifiying the problem tappets is not as easy as it sounds, the racket of the drivetrain making it hard to pick the duff ones out. Last time I checked a single tappet (you have 16 of them) was about £20, so you're looking at a £300|PLS| bill if you want to replace the lot, plus associated other charges. Whether you try to identify the offending tappets or just replace the lot, this can be judged as an moderate-to-very expensive excercise in futility: some have tried this and found the problem back within a few thousand miles! Not really the route I'd go.
2) Clean them - There is a
well documented procedure for cleaning the tappets, expect a busy afternoon and oil under your fingernails. The procedure is for a DSM 4G63, but the Evos are almost identical. the thing is, you're not solving the problem with this one either - the noise is almost bound to come back at some point. Which leads us on to...
3) Live with it! - It'll not surprise you to learn that this is what most of us do. Unless the noise manifests itself
all the time and doesn't even quieten after an oil change you probably don't have to worry. If you have excessive noise then it may be that some of you oil pathways are blocked, starving the top of your engine of oil. I use the noise as a sign that my oil needs changing. Most of the time you should only get a few minutes of noise after startup and maybe the occasional light tick at a set of lights.
To minimise the noise use a good quality oil of not less than 15w40, the commonly available synthetics (Mobil 1 etc.) in 0w40 ro 5w40 grades are too 'thin' and can make the problem a
lot worse. Castrol RS 15w50 used to be the oil of choice around here, although they seem to have stopped making it http://www.ltregister.f9.co.uk/graphics/sad1.gif border|EQU| 0 align|EQU| absmiddle > Also, some say that cheaper oil filters lack the anti-drainback flap the the Mitsubishi and most decent filters have, meaning that the oil in the top of the engine drains down to the crankcase overnight, leaving the top end 'dry'.
Regular oil changes (at least following the recommended service interval) help too, as does minimising the time the engine is left idling, though this needs to be balanced with providing the turbo time to cool down after a run. In general 30sec-1min is enough.
Rest easy then, we are all in the same boat! Have I missed anything? Hope not!
