Shark Attack

Can someone explain to me how it can do this much damage? I dont even really know what the IMS does. I know where it is, But have no idea what its for.

rxjohn

Question for you Jake,

When doing an IMS upgrade, does your process involve replacement of both bearing and IMS? I thought I only saw IMS bearing replacment part on LN Engineering website.

Thanks,

goofballdeluxe

Wow, I just stumbled across this thread. Wow.

I never thought I'd be glad to spend "only" $8K on a new top-end for my 1996 993 C4S when the time comes.

Whether it's IMS on the 996, or weak valve guides on the 993, it seems that Porsche can't seem to get past design flaws that wind up costing the customer some major dollars.

My heart goes out to the OP.

AndyK

I have to think that if Ford Taurus engines were blowing up the way M96/7 engines seem to be, there would be a recall - or at least one of those "shame on you" reporters bothering Ford until they addressed the issue. No?

I think if there is a clear engine design flaw, Porsche should be held accountable.

jferrer1

http://www.autofarm.co.uk/engines/wa...led/shaft_tech

Interesting solution from our friends across the pond.

Macster

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.

15psi

Ford Taurus SHO V8 were WORSE! Ford didn't stand behind the engines and nearly all failed between 50-80k. 90~99% failure that took the engine out. It was a Cosworth/Yamaha/Ford design.

(BTW- our transmissions and IMS shaft use a "press-on" design, but not sure if it is exactly the same engineering. There are places that will "pin" the IMS sprocket for you. SHO guys found tack welding, solved their problem. But most owners didn't know about the problem - you don't see high mileage V8 SHOs. )

Here is the shory history...
Cam trouble
Soon after the introduction of the SHO V8, widespread problems with the cam sprockets began to surface. Ford had used a relatively unusual method, called "swaging", of affixing the cam sprockets to the camshafts. The cam sprockets were fastened to the hollow camshafts by forcing a metal ball which was slightly larger than the interior diameter of the camshaft through the center of the camshaft, thus expanding the metal slightly and creating a mechanical bond between the cam sprocket and the camshaft.

This method proved to be inadequate, and the cam sprocket could break loose from the camshaft and spin independently from the camshaft (or "walk"). This would result in the camshaft stopping and thus not activating the valves, allowing the pistons to hit the valves, ruining the engine. The preventive measure of welding the cam sprocket to the camshaft soon proved to be a fix for engines that had not suffered such a fate yet. Another such fix is "pinning" the cam sprocket, or inserting a pin in the sprocket to keep it aligned on the camshaft. Ford issued a TSB (TSB 03-14-1) prescribing the application of Loctite to the cam sprocket to lengthen the life of the camshafts, but as SHO owners have experienced cam failure after the application of Loctite, most SHO enthusiasts do not recommend this fix.

I think the bigger problem is that Porsche never figured what the root cause was. They covered the engines during the warranty period, as promised. But should of figured a fix. It appeared that they kept trying with all the revisions to the IMS, but never fully succeeded. Eventually getting rid of the IMS in 9A1. It cost them dearly with the cost to replaced engines and then ship to Germany to inspect. I find it strange that you can't buy a replacement IMS bearing or the center bolt from Porsche. (or so I understand)

Kind of ironic that a couple of guys in the US appear to have figured a 'fix'.

gerry100

I'm looking an an 06 Boxster S and the IMS is an issue I'vr got to worry about.

As an act of tough love for Porsche we should park a Honda S2000 in their lobby.

If Honda ever refocused on building sports cars, Porsche could be toast in 5 years.

jw97C2S

OP
You should consider hiring a lawyer. I know the last thing anyone wants to do is pay a lawyer for something but it would probably be worth it. You could potentially recover your attorneys fees also. My guess is that Porsche would settle since they wouldnt want the number of failures/different models disclosed and published(obtained through discovery).

I filed a claim with Porsche years back under their corrosion protection warranty. Porsche refused to cover the claim but as soon as I hired a lawyer, the claim & attorneys fees were recovered.

Jake Raby

Either.

The original fix that we created could ONLY be applied to engines that were completely apart for rebuild or totally torn down to repair an IMS bearing failure. With the engine disassembled we have the ability to machine the IMS tube for another third row bearing for the ultimate in bearing durability and total overkill engineering. EVERY new engine I assemble gets this procedure along with 3 other proprietary alterations that are made to the IMS shaft while it is accessible. This is known as the "IMS Update" (or IMSU) as it doesn't just enhance the bearing, but enhances the entire shaft.

The IMSR or IMS Retrofit is a bearing removal procedure that extracts the original bearing from the IMS tube with the tube still installed into the engine and the engine still installed into the vehicle. This is the procedure thats the hot topic in this thread.

The IMSR allows engines that have not failed to be outfitted with bearing technology that is over 1 decade more advanced in materials selection than the OE bearing. It also allows engines that are showing symptoms of bearing failure or have experienced complete bearing failure (and caught in time with the engine shut down) to be "saved".

The IMSR DVD will go over the shaft, what it does, where it is located and why it leads to such catastrophic failure when the bearing that supports it goes south.

soverystout

I was a victim of the V8 SHO. My first new car. Bought in 99.
Trans blew at 14K. Tie rod ends, ball joints, rack and pinion all failed.
Normal highway daily driving. No mods or racing of any kind.

My Lemon law suit got me a few grand and I tookt he car the next day to the Honda dealer and bough a 01 Prelude. Great car that honda.

Jim Griffin

One avenue that everydody with a either a RMS or IMS (in the past or now) failure should follow is filing a complaint with the Better Business Bureau, under the Lemon Law. Just Goggle BBB Lemon Law and you will find the on-line form to send to the BBB. IF everybody does this and the BBB gets enough of these they will follow up with Porsche. And by the way, Porsche does not participate in the BBB...wonder why? I had a 79 Oldsmobile that had a flat cam on #3, due to a manufacturing problem. I took it in to the indy to find out why it had so many problems. Come to find out there were 3 things that were manufacturing flaws in the car: 1. the cam, 2 the X-100 Tramsmission and 3.a faulty distributor. All three were covered for parts and labor by GM. I left the garage only owing for the cost oil change and some new plugs. This was done completely due to the BBB Lemon Law filing suit with GM on behalf of its customers.

AndyK

After reading about it on Jake's site, it seems the IMS bearing is the same Achilees heel to the 911 as the dreaded cam chain tensioner was/is on the 16 valve 944 engines (it's a lot easier to replace the latter for preventitive maintenance)!

jferrer1

Jake,
What are "engines that are showing symptoms of bearing failure"? The dreaded Porche IMS failures on the 986,996,997 and Cayman sounds like a Porche public relations night mare if the general public was made aware of such a design "flaw". There are thousands of these cars made since 1997 yet we all sit and wonder when we are going to be the next victim of an engine failure. Using the right oil, running the car properly, keeping the maintenance schedules, etc....nothing seems to reduce the probability of an engine failure. Either the IMS closed bearing is going to leak and you are screwed or it does not leak and you are safe. Most of us are proud Porche owners and would like to see a remedy to this catastrophic nightmare and hope it never happens to us. A couple of smart US engineers have a "solution" that Porche does not acknowledge. Hell this is beginning to sound like a bad reality show. Unfortunately the reality is on us to do something about the problem instead of looking the other way and hoping the "next" engine swap is not yours. Do we have any clout as a community in the US marketplace for Porche to take these allegations in design flaws seriously? In the era of information overload I bet there are many ways to educate the potential sport car enthusiast of the Porche malady.

Vifa

I am beginning to get a little bit nervous. I have read all 9 pages of this thread now. I am not mechanically smart so I do not understand everything about the IMS issue.

"Do I have anything to fear" seems like a stupid question now.

But, srsly, can I do anything to prevent this failure ?