Boxster, yes, no and maybe. The IMS will fail. The dual row less than the single. Some fail at 15k, some are still fine at 200k. There is no way of knowing where on the time versus failure probability curve your particular sample will fall. Nor is there any way of knowing how much risk your specific installer and his experience/skills/tools would add or subtract.

Roll the dice.

All '99 Boxsters, with original engines, have dual row bearings.

Data from the IMS class action lawsuit showed less than 1% of OEM dual row bearings had failed.

Dual row OEM bearings fail typically when their outer seals degrade and leak.

Outer seals degrade when they are exposed to contaminated engine oil for long periods of time.

You may want to replace your dual row bearing before replacing the clutch if you haven't changed oil frequently (once a year or every 5000 miles whichever came first), you've let your car sit for long intervals between drives, or you/ve tended to take many drives where the engine hasn't run for 20 minutes or more at operating temperature.

If you're worried, replace the bearing now.

The 99s are dual row, they are not prone to fail any more than any other part in the engine.
The rods will fail too, eventually.
I think its more PR to tell anyone with a Boxster to hurry out to your approved IMS bearing installer and have it switched out asap regardless of the year.

We have a couple OEM dual row customer's that would disagree with you as they had to replace their engines when the "not prone to fail" IMS bearings killed their otherwise fine M96's.................

JFP's implied guidance is spot on. Approximately 375 OEM dual row IMSBs failed in the United States up through 2005.

I have been running the single row bearings on a test jig to see how they are failing and may have something that may be interesting. With the standard single row bearing, the cage is usually made of two strips of metal riveted together to form the cage. My testing has shown that this type cage comes apart after only 10 to 15 minutes at about 5K rpm (no lubrication). So I transplanted a W type, or crown type cage used in the double row bearings into a single row bearing and ran it at 5K for 30 minutes with no signs of cage failure, and the balls still have a mirror finish (no lubrication). I am going to take the bearing apart to examine it and then get it back on the test jig for more running.

Spinning the bearings unloaded doesn't tell you much of anything. You do realize how much engine RPM would equate to 5,000 IMS RPM, correct?

The only "jig" that works for this sort of testing or development is a running engine. Its called the M96.

2 hours later, the balls have lost their mirror finish, and I can move the balls a little bit within their cage cells. But the cage still shows no signs of failing.
It's a little hard to keep the rpm up to 5k now because the bearing is beginning to vibrate a lot.

So if I run my engine with no oil, at the RPM that would spin the IMS at 5k RPM, your testing shows that it will last about 2.5 hours? (The bearing, not the pistons)

Seems more people change water pumps more often than IMS. Maybe test those?

Out of how many manufactured? 375??? Lets see, every Boxster produced between the years 1997 and 1999 had a dual row, some cars from 2000 had a dual row. How many cars is that??
Sounds like just as much chance as cylinder linings cracking...Hurry, go rebuild your engine just in case.
I don't know guys.....

So based on a couple of bad ones EVERYONE should have it done ASAP???
And how much do you charge for that?

Look I realized its something that should be pointed out, but on models of cars where failure isn't prone I don't think the chicken little routine is necessary.
I think some people are over dramatizing this on the dual row cars.
Single row yes, I agree, much higher failure rate.

I am simply stating an observed fact: All ball bearing IMS units have some level of failure potential, and that the dual rows do fail and take the engines with them. We have had personal experience with failed single row, dual row, and even the oversized post 2005 units. The risk is real, and how people respond to those facts is entirely up to them and their personal level of risk aversion. Not everyone can afford to jump for a new bullet if their current engine suddenly dies, and some people intend to keep these cars for a long time, so they adjust their priorities accordingly. No one is holding a gun to their heads. And if you choose not to do anything about yours, well, that is your business.............

Walter White, Jake is spot on with the comment that spinning an unloaded bearing does not reflect what is happening in the engine. Ivory tower bearing life (all other things being equal) is related to load and RPM. The implication is that operating temperature lubrication, vibration, contamination are all nominal for the bearing. Take a look at bearing manufacturers design handbooks for more information. The reason I did not perform an L-10 calc for the IMSB was because the load would have to be an estimate making the result worthless. By the way, RPM is at 1/3 crank speed. As far as changing the IMSB, Porsche should have manned up early and declared it a maintenance item, particularly the single row :barf:. As has been pointed out below, every part of a car eventually fails, the trick is to understand required maintenance to head off collateral damage from failed parts. To reduce the chance of IMSB failure in my engine, the intermediate shaft was modified and the bearing replaced with a high temperature C3 single row bearing. The bearing will be changed out as if it were a timing belt. That means scheduled bearing replacement, something Porsche dealers should have been doing years ago.

You say that like every person drives the same way.

How many IMS online complaints have I read that started out with "I was doing 20 mph when it failed, and really never drive on the freeway at all, let alone in higher RPMs.." thinking that would help their case?

Two identical bearings. Two drivers. Two different potential results. Now, how many cars were made total?

I change the oil every year. I hardly use the car, sometimes it sits in the garage for about 2 months. When i change the oil my mechanic jokingly tells me that he feels like selling my old oil to someone else, as it's colour is that of brand new oil,sometimes with as little as 500 miles on it.
I still make it a rule to change it every year though, and inspect the magnetic drain plug and oil filter really well.
So do you think i should change the bearings because i don't use the car much?

I had a suspicion that my mechanic was putting used oil in my car! It's yours!

Bench-top testing isn't as futile as some would think. The first bearing I tested, I had no idea what was going to happen. I figured that maybe a few hours, maybe days, or even weeks, the bearing would begin to vibrate, wobble, screech and then maybe come apart with balls looking like raisins. But when that first piece of the cage came flying out of the bearing after only a matter of minutes it was a total surprise, I just didn't see that coming, literally. Then when I saw pictures of failed bearings with the cage broken in exactly the same areas, it got me thinking in a whole different direction.
Along those lines, I was wondering if the idea of drilling some holes in the IM shaft to equalize pressure has been bench-tested. It doesn't seem too difficult to set up. A piece of 2" PVC pipe, capped at both ends with a grommet in the center of one cap, slip a piece of tubing into the grommet (with a little grease) and connected to a manometer or a bottle of water. Spin the thing at maybe 3k rpm and see if pressure remains equal.

No. I'm simply saying that the evidence for OEM dual row bearings suggests that the odds of failure increase in cars with longer oil change intervals or low use. It's unclear by how much the odds. If your worried and plan to keep your car for a long time, upgrade the bearing and put the problem behind you.

Keep experimenting for another decade, then we'll compare notes.

Cage failures are generally collateral damage.