matt_o_70

if this were true - id be thrilled. Are head gaskets on the M48 known to leak oil into the #6 cylinder? intake refresh was done a few years back with coolant tube update.

Anyone have experience with any of the USB borescopes on amazon - for cylinder inspection?

I suppose I'll go put the leak down tester onto #6 a see what happens...

Jonathon Rolstin

The problem with leak down or compression testing an engine that is starting to show signs of the failure is that the failure starts at the lower part of the cylinder. You won't necessarily notice it in a leakdown/compression test since they are done with the piston at TDC.

If it passes and you know you are having issues, put a scope in the thing.

JR

Flat6 Innovations

These problems start at BDC, under the crown of the piston. The dwell time of the piston and changeover from down to up motion makes the piston rock, and load more at this position. This is also part of the cylinder that warms up slowest, as it is out of the coolant path, so it stays in a contracted state longest.

When the issues begin, and all that's apparent is the ticking sound, 100% of that sound is occurring at BDC/ changeover. This area of the cylinder is not visible even with the piston at BDC, as the piston covers the area up.

The only way issues at this stage can be found is with the suspect piston at BDC, with the oil pan removed and a very specialized medical grade boroscope with a super thin probe being passed into the cylinder from the opposite side.

These are the reasons why most every engine we see that has failed, has been misdiagnosed.

The borescope will only show cylinder wear in advanced stages, after the engine has started to eat oil. Why? Because as the cylinder and piston skirt are damaged, that damage emanates up the bore due to the damaged piston skirt traveling through other regions of the bore.

endless_corners

What is "normal" oil consumption for 100k+ engine?
na 4.5l

69gaugeman

There is another thread that Carl started where he rebuilds and supplies new pistons for 5k. Porsche changed the process to etch the walls instead of conventional hone and plated the rings with a diamond coating.

My 04 turbo with 240,000km uses about 1 litre every 10,000km

opxz

How long do you think it takes from the initial damage until you get the prominent ticking sound?

Jake Raby

This varies across the board by a huge amount of time and miles. The higher the mileage the engine, the longer the symptoms take to make themselves clear.

I'd guess that after initial damage that the engine goes less than 5K miles before the symptoms appear. I think that most damage occurs i Jan- Feb each year, and we start etting reports in April, and May/ June is fioed wth them.

gnat

Jake, I don't doubt you, but I don't understand this.

To look at the offending bore from the back side, would the piston need to be a TDC? If it's at BDC wouldn't it still be hiding the cylinder wall from you? Or is it the piston itself you are inspecting at that point?

69gaugeman

I'm sure he meant put the piston at TDC and look at the cylinder wall from underneath.

Flat6 Innovations

Yes, the opposite from what most anyone will do... They approach from the spark plug and simply cannot see the most problematic area, where the wear starts.

gnat

Yeah that's what I figured which is why I was confused. I know Jake's reputation well enough to know that he could have just as easily had some trick that was beyond my less than mundane knowledge of engine repair though

opxz

An update to my issue (2004 Cayenne S 90kmiles).

Dealership refused to assist. Contacted Germany directly, got a more polite refusal. Talked to the car owners association, their tech showed sympathy but no solution. My lawyer said that if I can present the fault as a security issue, I could have a case. That'd mean it would fall under a different category of laws.

Also talked to the motor specialist workshop that the dealership uses and they've changed 3-4 motors for the dealership due to this. I'm getting a list of the cars over here, they're not that many. If successful, I'll be making phone calls to each and every owner to ask if they've had issues.

Stirring the pot, seeing where it takes me.

mclaudio

I'm wondering if the NA V8 engine scoring issues has largely been addressed from model years 09 onwards. Does anybody know? Has someone here experienced scoring issues with their 09 and newer Cayennes?

dryadsdad

Check with Flat6 Innovations. He'd know.

endless_corners

Well 2008+ NA v8 is 4.8l and not the original 4.5l v8 that seems to experience the most failures. The 4.8l NA doesn't fail at a statistically significant level as far as I can tell.