Engine Failures Illustrated

We are currently creating a data base of engine failures and attempting to establish trends that will make it easier to address engines with upgraded components... If you have experienced a failure, This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Below are just a few of the failures we have noted during the development of our program. As time allows we'll be sharing more of these with pictures and explanations of each mode of failure and how it could have been avoided...

Remember: Breaking components is part of making something better, to an Engine Developer there is no negative failure! Each has its own personality and is beneficial!

Timing chain link failure. 1998 2.5 Boxster, only 30,000 miles. The piece of the chain roller link was consumed by the evacuation pump in the cylinder head, immediately lodging itself in the pump, breaking the drive tongue and coupler. In the process the exhaust valve's timing events were advanced and all the exhaust valves collided with the pistons, bending the valves.

This was an instance where a timing chain failed at 1/2 life and lead to another failure without chain breakage. This failure has inspired development of better timing chains as well as a filter screen to prevent debris from being consumed by the scavenge pumps.

Rear of engine, IMS (intermediate shaft) and RMS (rear main seal) shown. Upon disassembly, engine had updated rear main seal. Engine has early style IMS with smaller diameter nut. Dry RMS but oil collected around IMS and case bell-housing possibly sign of impending IMS failure.

Signs of factory repairs to engine case consistiing of welding and grinding. Again, same engine with 30,000 mi. Apparently, rather than discarding imperfect cases, they were rebuilt at the factory. There are more pictures below of another 2.5 case showing similar repairs on what was an original factory engine (not a reman). Why would the factory make such shoddy repairs??

Variocam tensioner from a 2.7 with D-chunk failure. Approx. 70,000 miles. All other tensioner guides in this engine were just as delaminated and worn. To solve this issue we are visiting other materials to "shoe" the guides with that can allow for wear resistant coatings to be applied.

This was our most suprising find in the engine with the cam chain link failure. Closeups show excessive cam sproket wear, especially with only 30,000 miles on this 2.5 engine. Similar to wear experienced on 944 cams, requiring resproketing of cams or replacement of cams altogether. Excessive variocam pressure on chains and tensioners is one possible source of wear and chain failure. Since we don't know what wore first, it is also possible it was a lubrication issue with inadequate oil film strength or lack of anti-wear additives.

Powdered metal technology rod. These rods, being cracked cap technology, are not rebuildable. Beautiful idea for Porsche, horrible for an engine rev=build and thats exactly what they were designed for! Inexpensive to produce, strong for a while and then you throw them away!

1999 3.4 996. Classic D-chunk failure. When cylinder failed, engine hydro-locked. Block shown is the first type we've seen documented, cast as a single liner, with an etched bore, like aircooled alusil cylinders, dubbed lokasil.

1998 2.5 986 Boxster. Previously unseen cylinder failure. It is a known fact that the casting plant that made the blocks for Porsche was unable to keep up with demand and also experienced casting problems, turned to a 3rd party with a freeze-cast MMC (metal matrix composite) liner which was cast into the block. Sleeve had a very small lip at the head end to keep it from moving. On this cylinder, the lip broke, allowing the sleeve to intrude into the crankcase, leading to a D-chunk failure coupled with a delamination of the cast in liner from the block.

In the above engine that had the sleeve delamination and also D-chunk failure, all cylinders were sleeved. But to our suprise, in another 2.5 engine we disassembled, we determined that the case had been repaired by the factory. Not all cylinders had these cast-in MMC sleeves installed, only one, which had similar paint on the cylinder in the water jacket that was sleeved. More importantly, this block also was beginning to have the MMC sleeve coming loose, as shown below at the crankcase end, with a sizeable gap between the liner and the block itself. Note the blue paint presence on this bore, and the same blue paint around the area of the case above that had been welded.

The factory KNEW these engines had issues, this isn't the same company that created the 356 and 911.


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