[rl968]

I am hearing some clatter/tapping coming from under the valve cover, almost like a light knocking. Anyone know what this might be? I have 0w-40 in it and chain, pads and sprocket were all good in January when I last removed the valve cover so that is not it. Lifters maybe? Car runs very strong and does it hot or cold.

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[Cloud9...68]

It sounds like it may be lifters. Does the sound diminish at all when the engine warms up? These engines are pretty noisy, so it's sometimes hard to tell what's making the noise, and whether what you're hearing is "normal" or not. My car was making lifter noise when it was cold, but it would pretty much disappear when it warmed up. I'm in the middle of an engine rebuild, so it will be interesting if the noise disappears altogether simply by virtue of the head being cleaned up. Some of the lifters were "stuck" in their guides tighter than others, so the machinist thought that cleaning everything up might help eliminate the tapping sound. How many miles are on your engine?

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[tamathumper]

<vent> @$#! hydraulic lifters. </vent>



Do you have an engine stethoscope? Grab a cheap one if you can - it doesn't help in every situation, but it can help to rule things out as much as in.

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[rl968]

I was at the track this weekend, and when I came off one time I started hearing the loud clacking noise, pretty much stayed that way so definitely can rule out cold temps. Also definitely not normal. 137k miles on the car. Like I said, car was pulling very strong through all gears (3,4,5), no hesitation and good acceleration.



What's involved with changing the lifters? Is it a time consuming and expensive thing to do? Do the cams have to be changed as well? What else gets done "while you are in there." I'm not looking to do a substantial engine rebuild...yet!



Thanks

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[Cloud9...68]

The cams would definitely have to come out to get to the lifters, so it crosses the threshold into a "big" job. And I'm not sure you can do much with the lifters without removing the head, since a machine shop would probably want to check the clearance of the lifters inside their guides. Before tearing into something like this, you'd probably want to take it to an experienced mechanic to have a listen.

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[AJG]

A quick and easy way to listen to the lifters is to hold a srewdriver to the engine near the lifters and put your ear to the handle end. You will definitely hear something and there may be differentiation between each lifter to clue you into whether they are sick or not. A bit crude but cheap!

When you listen to rotating ball races in this manner the difference between a "swishy" sounding good and a rattley bad one is quite defined.



Andy

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[Cloud9...68]

The more I think about this, the more concerned I become (sorry, I seem to be in an excessively negative mood for some reason...). The fact that the sound doesn't diminish when the engine warms up agrues against a lifter problem. I'm wondering if you actually have a problem with your Variocam pads or chain. I just took my head off, and it has two significant vertical gouge marks on the inside wall right where the Variocam chain goes, so I suspect that earlier in its life, it suffered a Variocam pad or chain failure. If your Variocam drive mechanism is compromised, the clatter you're hearing may be a loose chain hitting something it's not supposed to, or just the sound of an excessively loose chain. Maybe I'm being a nervous nellie, but just to be safe, you might want to not drive the car until you remove the valve cover and take a good look inside the head. There's a great write-up on how to inspect you variocam pads, I think in the DIY section. If everything looks OK, I would take it to an experienced mechanic to have a listen. Personally, I've never had much luck with stethoscopes. Let us know what you find.

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[tamathumper]

Is your oil pressure OK? Low (or no) oil pressure in the top end will cause the chain tensioner to stay limp and your chain will slap against the inside of the cover - it's a hell of a "razzing" sound when you're accelerating, but if you're idling it can be a rhythmic slap or clatter because the chain is whip-sawing up and down... Just one of the horrible demons of a PO I had to exorcise.

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[rl968]

appreciate the replies, guys. Oil pressure is fine, it was reading above 4 on the track. I didn't hear the noise under acceleration only at idle. Pads and chain were like new in January (chain was tight) when valve cover was removed, and car has not been driven much until this weekend. The car was running very strong on the track, no deterioration in performance, temperature was at the first mark the entire time...except for the noise, you couldn't tell something was wrong.



Where is flash when you need him <img src="/forum/images/smilies/968/unsure.gif" class="smilie" alt="" />

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[flash]

sorry - been swamped - my first thought was the same as others have already expressed



that being said, i would not dismiss something just because it is new, in fact, that usually becomes my first suspect



is the oil synthetic? how old is it? 0-40 is a wide spread - i prefer to keep the gap to 30 for reasons like this - if the oil is not pumping up properly (the polymers expanding and all that) you might have a weak lifter not pumping up



is the sound rhythmic at all?

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[Cloud9...68]

Yeah, just to rule it out, I would take the 30 minutes to take another look inside the valve cover. It's free, and it can't hurt. The fact that the noise isn't worse when it's cold is what I keep getting hung up on.

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[rl968]

Mobil 1 synthetic, 0w-40. Changed in January when timing belt was done. It is somewhat rhythmic, but hard to tell, just sounds like a lot of clatter. I had 15w-50 in there previously, but when the car was cold it made a less distinct tapping noise. Changed to 0w-40 and that went away. This noise now is similar, but much more distinct and significantly louder. We will crack the valve cover to take a second look.



So do I go to 10w-40 keeping in mind this is largely a track car that will be in east coast summer temps.

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[tamathumper]

So many car forums have threads like this where people are trying to describe a sound, and others are asking if it's a "clatter" or a "tap" or a "whirr"... Can you post a recording?



(We should make a 968forums spot on YouTube where we can post videos of our cars making different noises for diagnosis, and eventually we'd have a great resource - a library of sounds so people would know what was wrong by referencing the collection. Granted the quality would not be perfect, but it's better than having to ask if it's a "clatter" or a "racket".)

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[flash]

the minute you are able to put away the snow boots, i would switch to a 10 base oil - in the summer, i would probably go 15/50, but at least 10/40 - the upper end heat tolerance is significantly higher, and if you read up on max temps the oil can handle, and then factor in the temps you will see, you might find that you have exceeded the capabilities of the oil on the track



as a guide, 10/40 is usually ok on the track up to about 80 degrees ambient - anything higher than that and you need to jump to a 50



all oils are not created equal either - as an example, royal purple breaks down extremely fast at high heats, amsoil and redline don't so quickly



before this becomes an oil thread, i would suggest reading up on the ones that are out there already



moving back to the noise, if it is rhythmic, i would be looking to the things that are cyclical - use the stethoscope to see if you can nail down its location (front to rear, etc) - that will help narrow down if it is the chain, pads, or a lifter - also, run up and down the revs - at 1500 the variocam engages and should alter the sound of the clatter if it's the chain - it may not be much, and probably won't go away, but it should be different - if the sound changes before 1500, you are probably looking at a lifter not pumping up

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[rl968]

the sound appears to go away once the engine is revved, I can really only hear it at idle.



This means lifter issue?

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[flash]

that would be my guess IF it goes away but not until well after 1500rpm, indicating that the sound is still there after the variocam solenoid has extended, which would eliminate the chain and/or pads as a culprit

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[rl968]

Hope this works. I've attached two links of the tapping, one at idle, one revved a bit. Hoping someone (Flash <img src="/forum/images/smilies/968/rock.gif" class="smilie" alt="" /> ) can give me more clues as to what this is. Car is at my mechanic's shop and while he knows Porsche's very well, the 968 engine is one he isn't that familiar with. Not many have experience with the 3.0 given how few were made.



http://www.youtube.com/watch?v=RwLqzsXM_wg



http://www.youtube.com/watch?v=nN98FY9CZ_8

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[flash]

yeah - that sounds like lifters

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[rl968]

all of them? Could it be a problem before the oil is getting to the lifters? are there any pressure valves that could be the issue? rod bearings? I'm afraid that i do the lifters and the noise is still there.



What's the risk of running the car like this on the track? Especially since it diminishes at higher rpms?



thanks

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[Cloud9...68]

The one at idle definitely sounds like lifters, but it's strange that the sound doesn't diminish as things that would improve oil circulation (temperature and rpms) come into play. Personally, I wouldn't drive it on the track, or anywhere else, until somebody qualified does a diagnosis. But it doesn't sound like bearings, which tend to have more of a "knocking" type of sound, iirc. It definitely sounds like something in the top end.

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