i cant believe it happened to me!!! UPDATE!!
01-08-2010, 07:49 PM
#137
Rennlist Member
Form what I understand No. To answer your other question, there is a company that makes a retrofit ceramic bearing. Its still a 10-12 hr job to replace and the kit is about 600. But even so, that is A LOT cheaper than another engine.
01-08-2010, 07:55 PM
#138
Rennlist Member
Briefly the IMS is a shaft the runs the length of the engine and resides directly under the crankshaft and is chain driven by the crankshaft.
The IMS in turn drives the exhaust camshafts in each head. These in turn spin the intake camshafts.
The cams turn at half the crankshaft speed so some sort of speed reduction is necessary. Furthermore Porsche engineers believed that directly driving the camshaft from the crank was not a good/workable solution, so the IMS (intermediate shaft) was chosen.
If the IMS bearing fails the IMS loses positional and location integrity. IOWs, the end where bearing resides moves about.
This movement can result in either the chain from the crank skipping/jumping a tooth or two which means the cams are not in time with the pistons moving up and down in the cylinders.
When this occurs valves and pistons make contact with disasterous results.
Or one or both chains from the IMS to the exhaust camshafts skip or jump a tooth or more which again results in the valves opening/closing at the wrong time relative to the pistons' movement up and down in the cylinders.
In another scenario the crankshaft chain snaps which means the IMS does not turn at all and the valves remain in whatever position they were in and pistons and valves make serious contact.
Also, in this case with the IMS also driving both the scavenge and high pressure oil pumps and with the IMS not turning there is no oil being pumped so the engine runs with just residual oil and no oil pressure to speak of so.
Or a cam chain snaps and one head's exhaust and intake cams stop turning. Again valves and pistons make contact.
6 of one half dozen of another.
There is no real escaping serious engine damage in the event of an IMS failure unless at the first signs the engine is shut off and not even cranked until the cause of the problem is sorted out.
Even shutting off the engine right away may not save the engine from destruction. It depends upon the severity of the IMS bearing failure, how fast this progresses, and the events that follow.
I've seen one 996 engine -- I have pics and posted one which shows the IMS and the end that houses the IMS bearing and which from the condition of the bearing races it is clear the bearing failed -- that it turned out upon inspection had suffered an IMS bearing failure but the driver shut the engine off as soon as noise was heard.
The car was taken to a Porsche dealer and upon teardown the engine's IMS bearing had clearly failed. An inspection of the engine found that the damage was confined to the IMS and its bearing and one chain guide/tensioner.
The engine was deemed salvageable and was resurrrected by a tech at the dealership.
I spoke with the tech and he told me -- this at least a year maybe closer to 2 years back -- that Porsche had only recently given the dealership's permission to do this. Before the engine was removed from the car, and a new engine ordered. The new engine installed and the old one put in the crate the new one came in and shipped back to the factory.
Sincerely,
Macster.
The IMS in turn drives the exhaust camshafts in each head. These in turn spin the intake camshafts.
The cams turn at half the crankshaft speed so some sort of speed reduction is necessary. Furthermore Porsche engineers believed that directly driving the camshaft from the crank was not a good/workable solution, so the IMS (intermediate shaft) was chosen.
If the IMS bearing fails the IMS loses positional and location integrity. IOWs, the end where bearing resides moves about.
This movement can result in either the chain from the crank skipping/jumping a tooth or two which means the cams are not in time with the pistons moving up and down in the cylinders.
When this occurs valves and pistons make contact with disasterous results.
Or one or both chains from the IMS to the exhaust camshafts skip or jump a tooth or more which again results in the valves opening/closing at the wrong time relative to the pistons' movement up and down in the cylinders.
In another scenario the crankshaft chain snaps which means the IMS does not turn at all and the valves remain in whatever position they were in and pistons and valves make serious contact.
Also, in this case with the IMS also driving both the scavenge and high pressure oil pumps and with the IMS not turning there is no oil being pumped so the engine runs with just residual oil and no oil pressure to speak of so.
Or a cam chain snaps and one head's exhaust and intake cams stop turning. Again valves and pistons make contact.
6 of one half dozen of another.
There is no real escaping serious engine damage in the event of an IMS failure unless at the first signs the engine is shut off and not even cranked until the cause of the problem is sorted out.
Even shutting off the engine right away may not save the engine from destruction. It depends upon the severity of the IMS bearing failure, how fast this progresses, and the events that follow.
I've seen one 996 engine -- I have pics and posted one which shows the IMS and the end that houses the IMS bearing and which from the condition of the bearing races it is clear the bearing failed -- that it turned out upon inspection had suffered an IMS bearing failure but the driver shut the engine off as soon as noise was heard.
The car was taken to a Porsche dealer and upon teardown the engine's IMS bearing had clearly failed. An inspection of the engine found that the damage was confined to the IMS and its bearing and one chain guide/tensioner.
The engine was deemed salvageable and was resurrrected by a tech at the dealership.
I spoke with the tech and he told me -- this at least a year maybe closer to 2 years back -- that Porsche had only recently given the dealership's permission to do this. Before the engine was removed from the car, and a new engine ordered. The new engine installed and the old one put in the crate the new one came in and shipped back to the factory.
Sincerely,
Macster.
01-08-2010, 07:59 PM
#139
Rennlist Member
Luxury cars don't hold value. Never had. Thats his fault for buying it. High perfomance cars do traditionaly hold a little more value.
01-08-2010, 09:05 PM
#140
Addict
Rennlist Member
Rennlist Member
I'd love to have you put in your new bearing, too bad I don't live in GA!
01-08-2010, 10:24 PM
#141
A few more questions for Jake (more 997 based but bear with me):
1. I've yet to find a definitive answer regarding when Porsche "upgraded" to the new style IMS bearing/IMS. I've heard some claim late 2005 and some claim mid 2006. The reason I ask is that for those of use looking at 997s, I've read that the later IMS design is NOT upgradable with your redesigned bearing. Seems as though a purchaser might be better off with the earlier design which is upgradable. Or perhaps the later bearing/IMS design is more reliable? (while I'd like to pretend this is true, I'm guessing these car are still too new to know).
2. What other mode of failures should one be aware of in the later engines. If I buy a 997, I'd like to address these before I drive the car.
TIA,
Joe
1. I've yet to find a definitive answer regarding when Porsche "upgraded" to the new style IMS bearing/IMS. I've heard some claim late 2005 and some claim mid 2006. The reason I ask is that for those of use looking at 997s, I've read that the later IMS design is NOT upgradable with your redesigned bearing. Seems as though a purchaser might be better off with the earlier design which is upgradable. Or perhaps the later bearing/IMS design is more reliable? (while I'd like to pretend this is true, I'm guessing these car are still too new to know).
2. What other mode of failures should one be aware of in the later engines. If I buy a 997, I'd like to address these before I drive the car.
TIA,
Joe
01-08-2010, 10:58 PM
#142
Burning Brakes
Since the bearing is sealed and there is no rhyme or reason to the failures and very little consistent trend date my scientific wild *** guess would be just how well each individual bearing was manufactured...
....thats nothing more than a wild *** guess.
01-08-2010, 11:20 PM
#143
Instructor
Join Date: Jul 2003
Location: San Jose, California
Posts: 183
Likes: 0
Received 0 Likes
on
0 Posts
There is a reason $70k to $90k cars are now selling so cheaply. The market has factored in the cost of repairing IMS failures, cracked heads, and the other catastrophic failures caused by superior German engineering.
01-08-2010, 11:27 PM
#144
Instructor
Join Date: Nov 2006
Location: Foothills of Shasta Cascade
Posts: 230
Received 0 Likes
on
0 Posts
Are you saying Porsches are depreciating faster than other high end vehicles?
01-08-2010, 11:41 PM
#145
Race Director
Join Date: Oct 2004
Location: KC ex pat marooned in NY
Posts: 13,005
Likes: 0
Received 14 Likes
on
14 Posts
Is any body rebuilding these engines, are the parts available?
Seems to me I'd try my luck with an old school race machine shop before I shelled out that kinda dough to a stealer, and just make it a long diy project.
Seems to me I'd try my luck with an old school race machine shop before I shelled out that kinda dough to a stealer, and just make it a long diy project.
01-09-2010, 09:16 AM
#147
Racer
Join Date: Jun 2004
Location: Brandon FL
Posts: 277
Likes: 0
Received 0 Likes
on
0 Posts
Yes, everything mechanical and or electrical will eventually fail (computers, launch vehicles, trains, planes and automobiles). Will your 996? 100%, yes it will, eventually, but you can take steps to reduce the risk, you can't eliminate them, but you can reduce it. Why do you think there are FAA mandatory aircraft maintenance and rebuilds hours, to help find worn/fatiguing parts and replace them. I just did a 105K miles maintenance that replaced all the chain guides, chain adjusters, RMS, IMS bearing/seal, water pump, AOS, and clutch. Why, because these items are known to fail and when they fail, bad things happen. 105K is a lot of miles, and now hopefully I can, with normal maintenance get another 95K and then think about doing a full rebuild.
01-09-2010, 09:21 AM
#148
Rennlist Member
I think he was talking about IMSF, Not "in general" I think he is smart enough to know that eventually, his engine will fail for some reason. But I think his queastion is more asking if every one is going to fail from IMSF.
My thought is no, you always get the one that runs forever... BUT, From what I am reading, I feel this is going to be the end of the road for a lot of them... I think pushing 90% if you dont take the proper precautions.
My thought is no, you always get the one that runs forever... BUT, From what I am reading, I feel this is going to be the end of the road for a lot of them... I think pushing 90% if you dont take the proper precautions.
Yes, everything mechanical and or electrical will eventually fail (computers, launch vehicles, trains, planes and automobiles). Will your 996? 100%, yes it will, eventually, but you can take steps to reduce the risk, you can't eliminate them, but you can reduce it. Why do you think there are FAA mandatory aircraft maintenance and rebuilds hours, to help find worn/fatiguing parts and replace them. I just did a 105K miles maintenance that replaced all the chain guides, chain adjusters, RMS, IMS bearing/seal, water pump, AOS, and clutch. Why, because these items are known to fail and when they fail, bad things happen. 105K is a lot of miles, and now hopefully I can, with normal maintenance get another 95K and then think about doing a full rebuild.
Last edited by Shark Attack; 01-09-2010 at 11:13 AM.
