Jfrahm

OK I checked and cleaned the pressure check valve in the head, it seemed fine. I removed the J tube and pressure tested it, no cracks. I checked and cleaned the check valve in the variocam unit under the J tube inlet, it seems fine too. Reassembled, started it up, no change.

If it was a lack of oil pressure to the variocam unit I would wonder if that would still be true when the engine is dead cold and the oil pressure is over 4 bar?

Also if the variocam pads are slapping up and down, oscillating between oil pressure and the valve spring pressure, I think it would be more of a clicking or clacking noise. This is more of a 'brrra.'

I could try rigging a harness to the variocam solenoid and triggering it when the RPMs are higher and thus the oil pressure is also higher. I'll try that if a solenoid does not fix it. I'd be out of ideas at that point anyway.

Thanks,
-Joel.

Luis de Prat

Hi Joel,

Please let me know what you find. I just did the belts and rollers on my S2 cab, properly tensioned both with the Arnnworx 920X and started getting this very same vibration shortly after. As a data point before you spring for a new solenoid, the S2 does not have the Variocam system. Coincidentally, my S2 just turned 160,000 miles and you say you have 155K on your 968.

I've pulled the front belt cover to see if anything was loose, although I conscientiously used a torque wrench on everything during the job. I removed the distributor cap and looked under the metal cover for the cam belt as well, but can't figure it out as nothing seems amiss.

There's no starter heat shield on this car either, for some reason, so I ruled that out as well.

Will be following this thread closely given that it's you who's trying to figure it out!

RajDatta

A possible longshot but did any of you have a misaligned lower balance shaft?
I have seen the oil pickup tube crack from long term misaligned lower balance shaft. This causes reduced oil pressure which creates the same symptoms.
Raj

Luis de Prat

Okay, can you elaborate on this? Sorry, but I don't follow you. I aligned all the markings when I did the belts with the engine locked positively at TDC, if that means anything.

Jfrahm

I have not personally checked the balance shaft orientation on the 968 but the PO's shop seems to have been oddly competent and everything has checked out good so far. Also I do not feel engine vibration that would alarm me. I am very sensitive to (and paranoid about) such things. Can't say as I have driven a 944 with one upside-down balance shaft but I suspect it's pretty noticeable, and the sort of vibration you could sustain at particular RPMs.

In my case this is a very brief and somewhat subtle noise.

I cannot draw the noise out, it always lasts the same amount of time. Always 'brrap' never 'brrrrraaaaaap' if I hold the RPM steady.

The noise has a slight snare drum sound to it, a little metallic rattle that sounds for all the world like a cat converter heat shield vibrating, but the noise is traceable to the head.

On increasing or decreasing revs, between 1500-1800 rpm depending on the throttle position or the rate of change of RPM perhaps. If I blip the throttle from 1000-2000 RPM, it's brrrap-brrrap, brrrap-brrrap.

Engine hot or cold, does not matter.

Disconnect the variocam wire and the noise goes away.

Cams, pads, j-tube, check valve, oil pressure relief in the head, all look good. The car operates normally.

It would not surprise me to learn the noise is 'normal.'

I might try setting the RPM at 2500 or 3000 and manually triggering the solenoid. I guess I could also try to get a sense of weather or not the variocam unit is actually moving. Maybe I can see a change in idle vacuum or something if I engage it at idle.

Thanks for the tips so far,
-Joel.

Luis de Prat

Can't say as I have driven a 944 with one upside-down balance shaft but I suspect it's pretty noticeable, and the sort of vibration you could sustain at particular RPMs.[/quote]

I've driven a 944 with an upside down balance shaft sprocket and the symptoms were constant vibration in gear or out, loss of power and no pickup when downshifting. What I'm experiencing now is completely different.

Joel, the description is exactly as if you were describing the sound in my S2, only I don't have a Variocam wire to unplug! I've gone nuts looking for the source, but no joy so far. Please pm me if you find anything!

RajDatta

Luis, in instances where the owner did not realize the lower bs belt/pulley was misaligned, it resulted in cracked oil pickup tubes. This can also manifest into lower than optimal oil pressures which can have the same effect on variocam.
Raj

FRporscheman

My friend's car does this exact same thing. He's just living with it for now...

968turbos2

Just another idea...did you replace the O-ring in the variocam valve cover flange and if so, did you replace the gasket as well with it?

Jfrahm

The O ring in the J tube to Variocam flange was fine, and I took a stone to the J tube flange to insure it was flat and smooth. The other end of the J tube uses crush washers. Not really sure what other gaskets or O rings you are asking about.

RajDatta

He is talking about the gaskets between the valve cover and the variocam unit if I understand correctly.
Raj

968turbos2

That's right Raj....Btw Raj...I always wanted to tell you that I chose the name before knowing you had this name. 16v turbo made me think 968 turbo s2 and it was available on first try. I always wanted to say that.

It was just a thought that the rattle may be that.

RajDatta

No worries on this end. Its all good .
Raj

Jfrahm

Update - I got a used variocam solenoid today and installed it. Same noise. I am convinced it is the variocam system activating as I can move the noise up and down the rev range by how fast I press on the gas pedal. That is to say with a quick stab I can get it to hit at 1500, with a slower depression 2000, and if I raise the RPMs as slowly as possible it comes in at 2300 or so. At whatever RPM and rate of change it's just a quick 'braap!'

Maybe it's normal, I am pretty sensitive to the little noises my cars make. I should go find a lower mileage 968 and see.
-Joel.

sergiomartins

in my car two years ago one day i started to hear a rattle coming from the variocam solenoid, +/- at 1500 rpm, if u try to replicate it with the hood open it happens about 2500rpm, cus the variocam only activates at 1500rpm when the engine is in load. but if i put my hand on the solenoid i could feel it rattle.
needless to say that everything checked out fine, although for good mesure i changed the pads,chain and oil check valve with o-ring, and still had the rattle occuring, until i before doing an oil change put some atf in the engine oil for about a week and gave it a good work out, when changed the oil for something a bit thicker the rattle went away, and even now that i went back to 5w-40 the rattle is no more.

PS: i also started to have nightmares about broken oil pick up tubes and so on... but last summer i rebuilt the engine(did not touched the variocam except for pads again) and nothing was broken.

PSv2: my car is in a shop for tuning and a custom remap and it was found lacking at least 20hp on the dyno ... the expert there reckons that the solenoid was erractic... new one on the way, then another dyno runs should shed some light in the matter.