Name this bolt! Multi-part, bazaar mode of failure! - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Stroked & Blown · 11-01-2010, 01:44 PM

OUCH! Looks like a rod bolt.
My guess is that the bolt somehow worked its way loose, gnashed the timing, and the material in the cylinder is from valve contact.

Jake Raby · 11-01-2010, 01:50 PM

The material in the cylinder, is the cylinder... After the rod bolt stretched, worked its way loose and fell into the sump where it was picked up by the timing chain..

The remaining single rod bolt wasn't enough to tie the mass together, so it broke and shot the cap through the top of the block. When the rod became disconnected it acted much like an axe and chopped through the bottom of the cylinder.

.......and some people are REUSING the stock rod bolts!

extanker · 11-01-2010, 02:08 PM

are you saying this motor ran for a time [it would take some time for the bolt to back out] with one con rod bolt

Jake Raby · 11-01-2010, 02:35 PM

Quote:

Originally Posted by extanker

are you saying this motor ran for a time [it would take some time for the bolt to back out] with one con rod bolt

Yes... And its not the first time we have seen this.. I have seen an engine run fine with one rod bolt shot through the top of the case! It was taken to a dealership and they didn't know what the bolt was or where it was from!

The engine ran like this for a good while, until the remaining bolt snapped from seeing double the normal load as it was trying to retain the rod cap all by it's self.

Look closely, the bolt in the picture never broke. Its also not stripped.. It literally fell out during engine operation.

.....and people wonder why the only engines I'll warranty are ours with full upgrades!

mikefocke · 11-01-2010, 04:14 PM

for the entertainment value they provide ... so many puzzles and weird failure modes for him to marvel over.

Jake Raby · 11-01-2010, 04:55 PM

Quote:

Originally Posted by mikefocke

for the entertainment value they provide ... so many puzzles and weird failure modes for him to marvel over.

My trophy shelf of blown up parts sure does grow quick! What took me 20 years to accumulate with aircooled failures I'll have far exceeded with the M96 in less than half that time!

I've never seen so much carnage from driving the speed limit!

Jake Raby · 11-02-2010, 07:14 AM

We finished the autopsy.. The entire bottom end of the engine was garbage..
AWESOME! Now to induct these onto the trophy shelf as offerings to the Gods of speed!

cnavarro · 11-01-2010, 04:20 PM

Quote:

Originally Posted by Jake Raby

Yes... And its not the first time we have seen this.. I have seen an engine run fine with one rod bolt shot through the top of the case! It was taken to a dealership and they didn't know what the bolt was or where it was from!

The engine ran like this for a good while, until the remaining bolt snapped from seeing double the normal load as it was trying to retain the rod cap all by it's self.

Look closely, the bolt in the picture never broke. Its also not stripped.. It literally fell out during engine operation.

.....and people wonder why the only engines I'll warranty are ours with full upgrades!

Just like the '06 Cayman the local dealership dived into. The rod bolts were finger tight! Probably would have suffered the same fate if driven any longer.