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But what if the cost is more like $7k for a used engine...

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Ins bearing
oldnwizr1 - 4 years ago
Have a 99 Boxer with 106k on it. Previous owner changed synthetic every 5k miles but never replaced
the INS bearing. Clutch replaced at 80k but declined the bearing. Car runs good. Should I put out the $1600 to
replace the bearing (peace of mind) or with that many miles, think it is OK? Opinions appreciated!
Re: Ins bearing
MarcW - 4 years ago
I think you mean "IMS" bearing...

It is KO. I often get my 2- and 3-letter abbreviations mixed up too.

You mention peace of mind. Is peace of mind worth $1600? Then do the IMS thing. 'course, IIRC depending upon which flavor you choose it is not a permanent solution but requires periodic replacement at I forget what miles.

Even after you spend the $1600 there are the other 30+ failure modes to eat at your peace of mind obtained by having spent considerable money to address just one of them.

You really have to make this decision for yourself. I'm obviously not a fan of this but other owners are and will advise you to get it done ASAP. And they could be right. Really I think it is a coin toss. That the engine has 109K miles on it suggests it has been used, cared for in a manner that seems to keep the dreaded IMS bearing fialure at bay. But that doesn't mean the bearing won't ever fail.
About 10% of all water-cooled Porsches (except the Turbos and GT3s) will have an Intermediate Shaft Bearing failure by 100,000 miles.
The percentage rises to 15% as the car reaches 150,000 miles and then tends to stay there.
That means that 85-90% of them will go beyond the cited mileage without failures.

If you just replace the IMS bearing you're not doing anything different. You extend the period but you solve nothing.
You will have to check/replace it every 40,000 - 50,000 miles except if you install the Direct Oil Feed (DOF) which actually cures the issue for the life of the car.
The cost of the DOF (installed) in a rear wheel drive, manual transmission Porsche is $2,300.00.

Happy Boxstering,

Pedro Bonilla 1998 Boxster 986 - 296,000+ miles: http://www.PedrosGarage.com
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

Racecar spelled backwards is Racecar
"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"
"If you wait, all that happens is that you get older"... Mario Andretti
"Being second is to be the first of the ones who lose" ... Ayrton Senna
10% failure rate I think is pessimistic or perhaps optimistic depending upon which side of the failure one is on.

From a rough/vague memory of some failure rates estimated from the class action lawsuit I believe the failure rate is much lower. Still not zero though.

Also, one has to consider all the other failure modes. Replacing the IMS bearing just eliminates (almost) that failure mode but does nothing for any of the others.
The lawsuit was years ago and worked out to about 1% per car year then. And I think Pedro's extrapolation from those figures make sense for the single row.

Is the cumulative probability of the other 20 something failure modes greater than that of the IMS? I have no data but would guess it might be.

How much to spend on preventative maintenance is something that, after owning about 50 cars, still doesn't present itself to me as a scientific decision but rather more an emotional one based on your personal makeup. Your financial assets. Your risk tolerance.

When I bought my '01S I immediately put about $3k into it in the way of a major service, brakes and tires. It still has its original IMS 2 owners later. But I bought it 2 years before the IMS became a common procedure. Were I to do it now, I'd probably do the IMS because it has become a well understood procedure if done by the right person. Which IMS kit I'd use is a thought for another thread but would be influenced by which one my mechanic was equipped to use and how many he had done.

Grant gee-lenahan-at-vee-eff-email-dot-net
Re: Ins bearing
db997S - 4 years ago
It's a crap shoot. My 2002 S saw the IMS go after 10,001 miles. I think there are others that have turned 200,000 with no issues. The problem is no one outside of Porsche knows the numbers behind the failures, which if made public, would help owners make an educated decision on what to do. My peace of mind was getting a new car in 2009 after Porsche designed the IMS out of their engines. My IMS went while on a road trip (midnight just outside of Toledo, an hour earlier, and I would have been in the middle of nowhere OH with temps at or below freezing). Your peace of mind could be just drive it until it dies--of IMS failure or other causes--and then buy a 2009 as a replacement. Who knows, you could get another 100,000 miles out of it without having to spend $1,600, and by then, 2009s will be dirt cheap. Or, you could get only another 10,000 miles. I think I'd pocket the $1,600 and put it towards AAA incase the engine does decide to implode while on a road trip.

Good luck with your decision.
Re: Ins bearing
oldhoo07s - 4 years ago
Can a distinction be made between the failure rate of the IMS in the M96 engine and the M97 engine? I am curious because I have the M97, in a 2007 Boxster S.
One has to be careful when describing things like probability of problems or failure rates to specify which they are talking about.

A 3rd generation bearing as in the '08 is the best of the 3 and the one that is the most cost to replace. So much better and costlier that few are replaced.
I live in a remote area in Muskoka Ontario,Canada and last summer hooked up with about 8 other porsche cars for a ride around our area.There were only 2 Porsche Boxsters on the ride plus mine.
I talked to the other 2,one was an 2010,and the other was a 2004.The owner off the 2004 told me he had a new engine in his car,i asked why and i told me the IMS blew and toke out the engine.
Approx 18 Grand $$ Cdn to fix.The car was mint condition.That scared the crap out off me.I think this IMS problem is bigger than u know!
I have an 06 Boxster S and when my clutch goes im doing the DOF and removing the outer seal on the bearing.I would purchase an 09 with no IMS but the cheapest
one ive seen is $20 Grand more than mine.I would do a bearing change for sure ,$1600 is nothing compared to the car being junk if it goes.
but i seriously doubt that "this IMS problem is bigger than u know!". We know a lot, including the failure data received from Porsche under discovery, which i provided (rough, from memory) above.

Here's the rub - do the math. Let's say the 10% overall likelihood of failure is roughly correct. Let's also say your $1600 figure, and $18k are correct. Then its close toa wash, with the expected value of one at $1600 and the other at $1800.

If you had been around reading for several years you would also have seen the writings of a professional bearing engineer who gave his observations on the root causes, and therefore what make sit more and less likely. I wont try to summarize since it involves adding my biases, an these discussions become "animated" too easily.


Grant gee-lenahan-at-vee-eff-email-dot-net
Or I can make the math work the other way with a $30k US engine.

Not sure it is a math driven decision. Pocketbook and emotion.
A used motor is risky. That said, I bought one. So i would use a new one for the plug.

A $30k motor is simply not a valid figure. That would be a custom race motor, and a very nice one at that.

Now, my entire point was that i used 8his* numbers and anyone can substitute their own. but its math, nonetheless.

Math == pocketbook by the way. emotion is another kettle of fish. Now, many will make the decision based on emotion;
but in those cases they need not ask questions of fact here.

Edited 1 time(s). Last edit at 02/28/2016 07:46AM by grant. (view changes)

Grant gee-lenahan-at-vee-eff-email-dot-net
Thanks guys, you have given me a lot of points to consider. Porsche put so many stipulations on replacing the bearings after the lawsuit that not many
were replaced. I have access to a BMW/Porsche dismantler here in San Diego and could purchase a used low mileage engine for a modest fee. What kills you is the labor to install it!
No one mentioned the "other problems with the engine.
Assume normal stuff like breaks, tires, normal maint.
Perhaps I should just wait and be surprised. The name of the recycling site is Autobahn.com...
And no the ~$30k motor isn't a race engine, just a very powerful fully rebuilt with all improved parts version designed to be a daily driver. I only offered it as an upper boundary. with the used motor to show how the math could change

(There is someone who bought one.)
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