#$@! Blew my engine today #&*#@!
03-03-2015, 06:59 PM
#706
Former Vendor
Your hole wasn't the same.. It was in the cam cover, not the block, like this one was.
Update from the morgue:
The engine is apart and it suffered a major failure. I'll post pics as soon as Kaley gets them uploaded to the file. The engine snapped the IMS drive chain tensioner paddle. Its hard to tell if the main chain is what shot through the case, or if it was a piece of the tensioner paddle. The block is toast and even the crankshaft, since all the chain slack heavily damaged the IMS drive. It also bent every valve, spun the drive on the IMS and etc. Its on the way to the scrapyard as soon as I finish the post mortem report.
03-04-2015, 12:23 AM
#708
Race Director
Thread Starter
I was wondering the same... you mean my motor? I'm wondering how all that damage could have been caused with no noise other than one relatively minor "thunk." One would think that damage would have sounded like an airplane falling on a house, or like Meghan Trainor, or something.
03-04-2015, 12:40 AM
#710
Race Director
Thread Starter
Interesting, here's a post by Jake from 10/20/2009 on 986Forum.com:
http://986forum.com/forums/performan...-within-2.html
http://986forum.com/forums/performan...-within-2.html
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.
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.
03-04-2015, 12:47 AM
#711
Interesting. This may be one more argument for a MK1 engine!
All I know is I haven't driven my car much in the last month but drove it today and damn if every time I drive it I fall in love with it all over again!!
All I know is I haven't driven my car much in the last month but drove it today and damn if every time I drive it I fall in love with it all over again!!
03-04-2015, 12:52 AM
#712
Former Vendor
Yep, your engine looks almost just like that one from 2009. I have seen this a few dozen times since then.
The plastic wear button was in ALL 996s, even the MK1! The only engines with a steel button were early, like 97 and early 98 Boxsters. I have seen one ROW 98 Euro model 996 that had a metal wear button, but never a US/ Canada model. Porsche had already had an accounting audit by then and realized that metal part was costing too much.
Cuda, did you ever hear chain rattle at start up with this engine?
The plastic wear button was in ALL 996s, even the MK1! The only engines with a steel button were early, like 97 and early 98 Boxsters. I have seen one ROW 98 Euro model 996 that had a metal wear button, but never a US/ Canada model. Porsche had already had an accounting audit by then and realized that metal part was costing too much.
Cuda, did you ever hear chain rattle at start up with this engine?
03-04-2015, 12:59 AM
#713
Race Director
Thread Starter
I suspect that it was the chain that slapped through the case, based on the chain imprint on the chunk that was knocked out.
So, to understand this better: As the tensioner button wears, the tensioner can't do it's job, so there is too much chain slack, and the slack chain flails around and breaks the paddle? Then either the slack chain or a piece of the broken paddle hits the case and busts through.... is that a correct summary?
.
03-04-2015, 01:16 AM
#714
Former Vendor
Nope, never, not once. And, I'm among the paranoid group that is ALWAYS listening for "funny" sounds.
I suspect that it was the chain that slapped through the case, based on the chain imprint on the chunk that was knocked out.
So, to understand this better: As the tensioner button wears, the tensioner can't do it's job, so there is too much chain slack, and the slack chain flails around and breaks the paddle? Then either the slack chain or a piece of the broken paddle hits the case and busts through.... is that a correct summary?
.
I suspect that it was the chain that slapped through the case, based on the chain imprint on the chunk that was knocked out.
So, to understand this better: As the tensioner button wears, the tensioner can't do it's job, so there is too much chain slack, and the slack chain flails around and breaks the paddle? Then either the slack chain or a piece of the broken paddle hits the case and busts through.... is that a correct summary?
.
What happens is this:
-The plastic wear button wears, usually due to the chain beginning to gain slack through wear.
-The wear button becomes so thin that the hydraulic tensioner goes out of range
-The hydraulic tensioner ends up over extending and exerting too much force on the tensioner paddle
-Things scatter
The OEM tensioner paddle is a weak link, BUT in this case the primary mode of failure was chain wear, its what created the entire issue and allowed things to go out of range in the first place. All the rest was collateral damage.
03-04-2015, 01:27 AM
#715
Interesing chain reaction (no pun intended). Could the wear have been caught by monitoring the cam deviations? With so much chain wear, the cam deviation should show a large value or at least some flutuations?
03-04-2015, 01:35 AM
#716
Former Vendor
Some things are a silent, symptomless death with this engine. Tick..Tick.. BOOM!
03-04-2015, 02:06 AM
#719
Nope, because the deviations don't exist between the banks of cylinders, since this issue retards ALL the cam timing, not just one bank. I have caught a few of these in process by mistake during IMSB qualification processes and the symptoms were very hard to note. I caught one chain almost ready to snap, only because I found one small piece of debris in the sump that came from the chain.
Some things are a silent, symptomless death with this engine. Tick..Tick.. BOOM!
Some things are a silent, symptomless death with this engine. Tick..Tick.. BOOM!
03-04-2015, 02:14 AM
#720
Former Vendor
What I meant is the cam deviation on each bank reported by Durametric, and not deviations between the two banks. The cam deviation on a bank reports the deviation from the expected relative position between the crankshaft (flywheel missing tooth as the reference) and the camshaft reluctor on that bank. So if both banks are retarded (with respect to the crankshaft), then we should see very negative cam deviations on both banks? Of course aything more negative than -6 to -7 degrees should have tripped a CEL.
You may have mode 6 values stored in the ECU at 6-7 degrees, but it won't throw a CEL until a 14 crank degree situation is experienced. The Durametric isn't capable of reading Mode 6 values, or seeing pending codes.
Put simply, I see cars here daily with blown engines that don't have a single stored code, or an illuminated CEL, and most all of them were "ready" meaning they hadn't thrown codes that were recently cleared.
The OBD port doesn't show most mechanical problems. People think that it can, and thats why I am booked for a year. These issues require a "mechanic" to solve them, not a "technician". That means engaging the ears, turning on the common sense, and opening up the tool box for something that doesn't have a cord attached to it.