All "IMS failures" are not IMS failures! Carnage within! - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Jaxonalden · 01-12-2009, 06:54 AM

Quote:

Originally Posted by Jake Raby

I had more pictures to post, but the software limited me to five..

Here are the pics of the two different tensioners. The broken unit came from the failed 3.2, the intact unit came from a 1998 2.5 Boxser engine.

Note the wear surface and the thickness of the tensioners.

It kind of hard to eye ball the thickness difference of the tensioners but I guess there is. I one thing I did see was the pot metal at the break. Those tensioners must be put under a tremendous amount of stress (I think of watching a motorcycle chain under power and then letting off) and to use crap metal is crazy.

So Jake, you think this could be the cause of some of the failures? Because of the carnage in a block after one lets loose that it simply is being overlooked and the blame is put on the IMS? If thats the case the fix seems so much easier to remedy.

kabel · 01-12-2009, 07:06 AM

Yowzers! Great write-up Jake, even I could understand that. And the pictures, wow, what carnage. Pictures are not just worth thousands of words but dollars too!

blinkwatt · 01-12-2009, 07:27 AM

Is this a part that an average joe with average joe tools can replace on his own?

Jaxonalden · 01-12-2009, 07:41 AM

No way, this involves engine removal and breakdown.

Jake Raby · 01-13-2009, 07:31 PM

We have to be very careful not to create a new problem while trying to solve another... This is something we fight all the time as we work to create solutions and what seems simple, generally never is.

Lots of the things inside this engine has simple fixes, but unfortunately this is not an area that is easy to access or inspect as it takes 6 hours of labor to access this component.

If we decide to experiment with bearings I'll certainly contact you...

Jake Raby · 10-20-2009, 12:38 PM

The second occurrence of this mode of failure in 10 months.. Yet again this one was misdiagnosed as an IMS bearing failure.

The IMS bearing is intact and has no symptoms of failure, but upon inspection we found a chunk of the IMS tensioner paddle wear pad in the oil sump. This sparked a boroscope interrogation of the IMS area through the IMS tensioner bore after the tensioner was removed.

The engine is not totally apart, but after I did a thorough inspection with the boroscope I can see that the tensioner paddle is missing it's plastic wear button and the entire wear pad has been ripped off and chewed up by the IMS drive chain. The remnants are laying at the bottom of the crankcase beneth the IMS drive as depicted here in these somewhat blurry photos from my boroscope from deep inside the engine.

The early engines had metal wear buttons for the IMS tensioer to rest against, that was too expensive so around 2001 this was changed to PLASTIC and when it wears thin and fails this sort of failure occurs since a ton of 'slack" exists in the IMS drive chain which causes the chain wear pad to be eaten up, resulting in an engine that has variable valve timing in a very bad way. The billet chain tensioner paddle that we have made with LN Engineering includes a STEEL wear pin that will resist this sort of failure; needless to say I use this in EVERY engine we build.

This engine is more than likely totally nuked. My forecast is that the majority of the pistons have had collisions with the majority of the valves and that most everything internally looks like 3 mile island.

More will be known when I complete the autopsy and fill out the failure report. For now it's clear to see that the IMS and chain are intact but that the wear surfaces and plastic wear button are FUBAR.

More pics later

Jake Raby · 10-20-2009, 12:59 PM

BTW- Here are some shots of the billet chain tensioner paddle vs the new, revised Porsche component.. Theirs is still plastic and cast aluminum.

Go overkill.

Here ya go.. These pics are of the newest Porsche revised part Vs the LN/ Flat 6 overkill component. Ours is the shiny, heavy duty one, theirs is the cheap cast aluminum one.

Shiny doesn't mean better, if you feel the difference in the weight of the parts alone you'd know the difference.. And you can't buy a new one with a STEEL wear pad for the IMS chain tensioner!