Mikes3.0cabturbo

My 3.0 16v S2 turbo had been running nicely until the HG went a couple of weeks back. I pulled the motor down to repair and only today realised the scope of the damage inside. However compression prior was 190psi+ and everything seemed fine. BTW only been under boost for 3,000mls.

All four pistons were scored/galled on the non thrust side I thinks that is what its called (anyway the downside), the other side was just shiny worn, gudgeon sides were perfect. The cylinder bores showed similar condition.

The gouging/galling actually looks worse than it feels, question for you more experienced P people, what would cause this to happen, I certainly dont want to rebuild and get the same again, the engine is only 100,000mls, two owner car always serviced, last owner did little mileage only used ocassionally. These engine are supposed to last for a long time certainly more that 100k...

rgds
mike

Luis de Prat

Wow, Mike. What a nasty start for the New Year.

Your convo has been such an inspiration for several of us that I'm truly sorry to see this happen and will be interested in learning what may have gone wrong.

I hope you can get it resolved soon!

Mikes3.0cabturbo

Luis now this has happended its an excuse to build it with more boost and stronger internals, I'm just trying to find out what could have caused this wear.
rgds
mike

lart951

Could it be related to the rings? wrong size?

333pg333

I think everything was stock lart. The motor hadn't been opened up or changed yet.
How do you determine the depth of the scoring on cylinders and whether it's ok to go oversize within the Alusil, or have to sleeve the block?

Mikes3.0cabturbo

thats right Patrick the engine had never been opened - was all factory

lart951

so it was a s2 engine that was turboed?

special tool

Was coolant being lost?

Mikes3.0cabturbo

Yes Lart its an S2 3.0 16v.

ST when the HG went I picked it straight away, in fact the oil was hardly contaminated by the time I stopped and there was still coolant in the overflow tank although low. The cylinder that went was number 1, thats has the least galling.

special tool

Let's see a good front view of those rods.

Mikes3.0cabturbo

ST, heres a rod front view, also one of the reverse side of the pistons showing the wear.

Also look at what was inside the sump, appears to be a very hard black plastic something that has been munched up not sure where that came from during its life - maybe something dropped inside during a service.

Vilhuer

Since all four cylinders have very similar scars its unlikely problem was water leaking into combustion chamber, unless it leaked into intake and got in to all four that way.

What was piston and bore size before engine was put together? Porsche tolerances are very small and maybe this setup was so tight that pistons simply expanded too much due to boost and this broke oil film on piston skirts. This could be problem especially if block and pistons were not originally from one single engine even though they all might be same tolerance group.

special tool

This is what I would conclude now.

Mikes3.0cabturbo

Erkka, was a stock factory engine never been opened and the leak was certainly only into cyl 1 for 10 minutes max before I shut it down.

Luis de Prat

Do the stock S2 pistons and related internals differ from their 951 counterparts in something critical that could have caused this?

People always value 951 rods for being forged, etc.