Doug_B_928

So, for clarification, the problem has been with the 4.5L S engine, not the 4.8L S engine, correct?

Flat6 Innovations

We have seen the issues occur with both. The 4.5 is most certainly the most problematic.

speed21

^ So what do you feel the cause of the problem actually is? How are the skirts causing the problem? And why in colder environments?

Flat6 Innovations

The problem is the expansion rate of the two materials. When the engine is cold the clearance is too tight and the piston expands faster than the cylinder.
An alteration of both materials and running clearance has been required.

speed21

Then that being the case wouldn't hotter climates exacerbate the issue?…cause more seizures?

Btw what clearances are they running stock? And why are the skirts seizing not the crowns? Combustion related temperatures will make the crowns grow first and abnormal Thermal i.e. insufficient thermal cooling will cause the seizures on the skirts/pin bosses.

Doesn't make sense…

Is the block parent bore or linered in the earlier engine. From what I've seen the later 4.8 is parent.

Flat6 Innovations

Makes all the sense in the world.. It's also very similar to the issues we solved with other modern Porsche engines before the Cayenne.

The skirt is the largest position of a piston, the crown is typically the smallest.

The pistons don't try to seize, the clearance is just right enough not to allow adequate kubrication just aftermarket up and the high silicon content piston expands faster than the cylinder wall as it collects all the "just started" combustion heat.

This is why these failures occur with longitudinal wear marks so heavily worn into the bores. This is also why the first symptoms are a tick that sounds like a lifter when the engine is cold.

There's always one side of the engine that wears faster than the other, because the factory only put one offset on the OEM pistons.

dryadsdad

Are there any preventative measures owners can take pre-failure to reduce the chance of that failure?

User 4221

Exactly how mine sounded. As the engine heated up, and all materials reached thermal equilibrium, the tick went away.

As it progresses, it sounds like a small diesel.

Flat6 Innovations

The best way to avoid the issue is to avoid cold starts in super cold climates by keeping the vehicle indoors. This is near impossible in some climates and thats why we see so much of this issue from Canadian Porsches. With the Cayenne being a year round vehicle these issues show up more with the engines than with 911s and etc that are seldom driven in inclimate weather.

The other issue is from a lubrication standpoint. However, my input on this topic is very biased and generally biased as I assist with the development of Driven Racing Oils offered by Joe Gibbs. Any input from a lubrication standpoint would take us way off topic.

Dyim

That is good to know. What about engine block heater, would that help?

Thanks.

mcbit

Heat undoubtedly is ultimately the cause of the scoring with local melting of the aluminium creating the presence of abrasive material in the bore. Though quite how the heating occurs is debatable. Conventional wisdom dictates that cast pistons though weaker than forged are more dimensionally stable due to being less dense and more porous. If the piston expanded enough to cause partial seizure the it would be likely to have scoring on both sides of the bore.

My own view would point to poor lubrication at cold start causing dry running of the piston thrust face against the bore and building excessive heat. The fact that the vast majority of vehicles survive this abuse even in cold climates suggests that there are other factors which push this undesirable state towards failure. These may include but are not limited to the following:

Oil too viscous for adequate splash lubrication at start.
Low oil level.
Poor oil condition.
Oil pressure relief valve relieving due to excessive viscosity.
Excessive idling after start-up
High revving after start.
Short journeys.

...and the list goes on.

In terms of 4.8 engines, I can only go by internet posts, the only on which I have seen was 08 turbo.

Flat6 Innovations

We are currently testing the effects of pre-heated oil and coolant in regard to these failures.

mcbit

Sounds like a plan to me!

nmercier853

Well I have a 04 S that started making the ticking noise about 500miles ago.It has 84K on it in and in excellent condition. I had the oil changed right away and I was hoping that it was a sticking lifter that would clear up. I live in a cold NE environment and my wife drives the car which she never allows it to warm up.

I am now in ****ty spot to either tear the motor down and look $4-6k or give it away for $3-4k to a mechanic. In good condition it was worth $12-15k. I can not see how anyone could justify spending $18k to have it fixed. I am sadly after owning several Porsches looking away from them. I have had everything from Cup Cars to Boxsters. The only one that has been consistent is the $200k Cup car that you rebuild every 60hrs

What is my best bet with the Cayenne?

Dan87951

If it was me I would dump it and sell it to a mechanic. I have seen S's on ebay dipping below 10k. Granted some of them have low 100k on the miles I'm seeing a downward trend with these cars as more engine failures are brought to light. If you do decide to get it fixed, speak to flat6 to get the correct piston to cylinder wall clearances before putting that thing back together.