RajDatta

Mike, you will be shocked when you look at the color of a new tensioner pad, its is pure white. The discoloration takes place from heat over time. I noticed that the tensioner pads have grooves which is a good enough reason to change them. They are very inexpensive for what they are worth ($25 or so each). Also change the chain as that is only $25-30 as well unless it was changed with the cam.
I was initially shocked when you told me your cams looked perfect but now it all makes sense. I think the chain and pads should be a 60K item on these cars or every timing belt change if you believe in 60K belt change.
Problem is that Porsche did not specify a strong enough chain for variocam. As Jay will attest, there have never been any tensioner/cam teeth failures on 928s yet S2 and 968s have them all the time. I believe that the chain stretches over time and starts chewing the teeth out. Also, the way the tensioner sit on the head is not a good design as it can literally sheer off the casting on the head. They also run higher oil pressres on the tensioner on 968s and S2s.
All these things account for a failure that is not present in other similarly designed porsche heads.
As far as the oil pressure relief valve, its is quite expensive. Also, your pressure is fluctuating and the relief valve makes sure that you don't go past a certain oil pressure and bleeds it or vice versa. Your idle pressures show that your relief valve is probably okay. Maybe a good cleanup is in order.
You know what happens when you start those while you are in there deals. Be careful!!!
Regards.
Raj

Fen

Both my 944 S2's have had the cams replaced because of missing teeth on one and failing case-hardening of the sprockets on the other. Neither had the tappets replaced - it's an eye-watering bill anyway without adding another £300!

Actually last time I got the whole thing done with a 48k service (so belts and tensioners) for £1,500. S2 cams are a bit cheaper but I have an ex OPC mechanic who charges £25/hr do my work.

BTW Alex - a few months ago I was driving in the A38 toward Bristol one morning (I work there) and a red 968 was behind me. It turned right at the traffic lights in Churchill IIRC - was that you? I was in a Mk2 Golf GTI so I didn't wave or anything.

mike_hammond

Just chucked in two pots of WYNNS lifter treatment, so watch this space, it may shift the crud thats causing the problems, but until I put a few miles on it I won't know.

Fingers crossed

Mike

Alex Cook

Fen - probably not me - my car never moves during the week. A chap called Steve down that way also has a red 92, so may be him.

Good to see more of the UK waterpumper massive on Rennlist - you shouldn't find your posts go missing here!

mike_hammond

Up the revolution brothers we will overturn the evil PCGB dictatorship .


Mike (With tongue very firmly in cheek !)


P.S. things are looking up since the Wynns went into the motor, its made a difference already in starting to settle things down, but I'll give it longer before I commit to anything concrete

Derek H

Mike,

If you intend to change the lifters yourself, I can lend you the flywheel lock and some first hand experience with cam removal/replacement. Send me a private mail at drholliday@compuserve.com. If you haven't already, take a look at the Variocam inspection procedure that Ugo Manfredi and I put together last year. It contains some photos of worn and new cams, that should help you determine the wear on your sprockets. From your photos, it looks like your exhaust cam teeth are worn but it's difficult to tell. In any case, I don't think that's likely to be the cause of your problem. I've been tracking Variocam problems (and tensioner/cam wear problems generally on 944's) since my first cam swap about 7 years ago and I've never heard of an intermittent tensioner/Variocam-related noise like you describe. I've definitely had the horrible diesel rattle lifter noise myself on two of my cars, both 944S2's, but not so far on either of my 968's. However, in both cases, it was on start-up after standing for a week or so, and went away, never to return, after a few minutes.

cheers
Derek

mike_hammond

Thanks Derek,

Your PDF was one of the first items I read on the subject, very good indeed, all it needs is a DIY replacement procedure and you've got a best seller

I will give you a shout once I know what I'm doing, it would be useful to discuss this with someone who has first hand experience of the beast.

The Wynns Lifter treatment seems to have helped a great deal so it's a wait and see thing over the next few days. If after a flush and oil change it does cure it short term, then I can plan my finances so that I can allow for sorting the top end out properly and perhaps address a few other minor probs at the same time.

I'll be in touch

Mike

Derek H

Mike,

I've just posted something similar on 968.net but I did write a cam chain/tensioner replacement procedure a few years ago for my 944S, and it's hosted on Clark Fletcher's website. Here's the link:

http://www.clarks-garage.com/shop-manual/cam-04.htm

There are some minor differences but it will give you a good idea of what's involved in the cam removal/replacement, and how to preserve the cam timing.

cheers
Derek

mike_hammond

Superb info once again Derek, hats off to you

Mike

RajDatta

Dr Holliday is the MAN when it comes to variocam. You are in good hands now and the best part is that you 2 are local.
Good luck with the lifter treatment.
Sterling, based on what I read about your car, you are not using variocam in its intended design but using it at a different settings to get optimum power, is that accurate. If so, you don't have to worry about it having as many problems as it will be static. Please correct me if I am wrong.
Raj

mike_hammond

Raj, your not wrong, its nice to have someone this side of the pond to call on for advise. We've exchanged emails & contact info etc so not doubt when I get started Derek will be getting a call.

Thanks for all the advise to date, much appreciated my friend

By the way, the lifter gunk has had limited affects, its still noisey on startup and when it gets up to proper operating temp at idle so its not a fix by a long shot, but it is quieter so at least it taken the pressure off short term until I've sorted the cash out for all the parts.

Thanks again Mike

RajDatta

Great, good to hear that it i working a little better. Let me know if you want used ones.
Raj

mike_hammond

So What Next ????? I'm back at square 1 !!!

I've spent all day stripping the motor down, replaced all the front seals, fitted a new oil pump shaft drive and seal. Fitted a full set of lifters, replaced the variocam pads. Put it all back together, with the balance shafts correct !! when I stripped it the lower shaft was 180 degrees out . Stripped the OPRV and replaced the 'O' ring seals. Replaced the oil filter, filled it up with fresh oil and coolant.

Turned the key and it started first time, great, the presssure built to 3 at idle the lifters quickly quietened down once the oil worked its way around. I did soak the lifters overnight and they were rock solid when fitted.
The pressure gauge read nearly 5 when throttled at 3000 rpm. But as soon as the engine started to warm up the rattle from the top returned along with some slight variation of idle speed and oil pressure sitting at around 2 - 2.5 varying with the idle speed. If I rev the engine gently the rattle subsides but as soon as you let of the pedal as it drops the rattle returns.

When its driven the rattle can come in even at normal oil pressure around 4 on the gauge, and tends to come and go depending on throttle position/revs. e.g. if you feather the throttle the rattle will come in as you gently release and then dissapear again as you push the throttle down, almost as if it dissappears when put under load.

It's definately a top end noise and the sound is as if someone has got a small jack hammer under the cam cover and hitting it around the variocam area.

I am at a loss now as to what this can be other than the chain tensioner itself ?


Help

Mike

Heyou

The only other noise like that i can think of is a small end rattle If i remember correctly, from my days of running cars until the engines expired, big ends rumble when under load and small ends rattle when feathering the throttle.

Maybe someone else will come up with a less expensive explanation of the noise, i hope so Mike.

Del

mike_hammond

I don't think its in the cylinders its coming from under the cam cover. I had a visual of all the valve springs and none appear to be broken so the only thing left is the tensioner itself. The J tube is OK and so is the check valve underneath.

Its got me stumped at the moment.

Mike