hvirvelsplat

New member here.
I got a 2008 Cayenne S 4.8L V8 (not the 4.5) with 120.000 miles on it. It has a very clear clacking or ticking sound. (se my video below). Its coming from drivers side, top of engine.
Before everyone starts going off on "cylinder scoring" - I am very aware of the 04-05, early 06 Cayenne S with the 4.5L V8 and my car does not produce piston slap, oil consumption, rough idle, or any codes. Borescope diddn't show any scoring. Piston slap is very distinctive in that it "rattles" more than it "ticks" and has an more uneven "rhythmic" sound changing with RPMs and whether engine is cold or warm. My car has a very rhythmic clatter. It follows RPMs up and down (kind of drowns after 2000-2500...ish RPM) and is present cold as warm

I suspect some kind of lifter or variocam issues. I've done some research but cant really come up with anything useful - most issues relate to the 4.5.
As far as I can come up with there seem to be some 4.8L variocam issues - but it seems to be related to 2010-2011 and upwards - regarding loose bolts.
I am looking for info on the lifter mechanism.
So far I can understand that the intake lifters are a "split" design where a pin in the lifter itself on the intake side, will hydraulic operate according to the Variocam - or am I wrong?
The exhaust seem to be a standard hydraulic lifter - I am hoping it only that since the intake lifter are about 270.- USD a piece....!!!

Any input wellcome, especially on dismantle, cam locks tools, timing gear removal...etc...

Any one else have this problem?

Thanks

jeff spahn

sounds like collapsed lifter. does it go away and did it start after sitting a while?

Dasblau

Had that prob with mine was running rich in the morning. I could smell the fuel. No codes and louder then usual. Replaced the PCV and problem was solved. I'd look for small vac leak any where from maf sensor back. Previous owner said PCV was replaced but there so cheap I thought it would be worth a try. Not sure when it was replaced last but it was far too long ago. There are fine tears and holes in the diaphragm as well

hvirvelsplat

Jeff: It does not go away. It has all the classic symptoms of a collapsed lifter. Not sure how it started - last owner parked the car once it happened and it diddn't run for about 6-7 months.

Dasblau: Its brand new - changed by previous owner, OEM receipt and I inspected it. Its not that part - and the car has no vacuum leaks. Already checked that.

thanks - keep em coming

TomF

I keep having to be the bearer of bad news and I am sorry to to tell you this, but that is clearly another case of cylinder scoring. At this point, if you do a compression test, one or more cylinders will be off by 30+ PSI. If you borescope from the bottom, you will see scoring at the bottom of the bore. See the recent thread (and there are more as well) about this issue.

While it is comparatively rare, it happens more with the normally aspirated engines than with the turbos. At this point, you might have 500 miles to go before catastrophic failure or you might go 2000 miles, but I certainly wouldn't take the chance.

Just for your edification, the variocam issue results in engine failure as the cam adjuster bolts shear off (the bad ones are aluminum). There is no warning, the bolts break, the valve timing goes nuts and there is catastrophic contact from the valves with the pistons.

Sorry for your misfortune.

deilenberger

How would one boroscope from the bottom?

The Variocam problems typically result in the valves touching and bending, apparently the 4.8 engine is not a collision engine, which is why Porsche has shops rebuild the heads if the remains of the broken bolts didn't cause any additional damage.

OP - I'd suggest investing in a mechanic's stethoscope ($3.99 @ Harbor Freight) and narrow down where the noise is coming from. Also - having Blackstone do an oil analysis should confirm or eliminate cylinder scoring as the issue.. if a cylinder is scored - metal will be high in the oil for sure.. (aluminum in particular, which wouldn't be the case of a bad lifter..)

nodoors

OP, I hate to tell you, but that sounds like piston slap to me as well. It is compression test time.

v10rick

Agree^^^
It has been reported here often that cylinder scoring may not be visible with a bore scope from the top, until the condition becomes severe.

Dilberto

Startup smoke is the rings, cold. The clacking is clearly piston slap. I'm guessing one of the 3 piston rings in each is shot. Does that startup smoke smell a bit metallic, or like stale oil?

19psi

He states at the beginning of the video the smoke is from the intake valve cleaning he just performed. Doesn't appear blue so probably correct.

But yeah....I'm guessing one cylinder is way down on compression.

TomF

Jake Raby and others do this though the pan. I suspect that it takes a pretty special camera to snake past everything.

Ah, I had forgotten and I do believe you are correct.

Cheers,
TomF

Dilberto

OP, did you Walnut-peen the valves or did you run Seafoam?

deilenberger

The only photos I've seen from below were of disassembled engines. Shot with a normal camera. I'd love to hear how they manage to get a camera up past the oil baffles below the crankshaft..

TomF

Me too... I took Jake's Cayenne engine class and he wouldn't share...



Cheers,
TomF

J'sWorld

Of course not.