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IMS Bearing Failure

krispe said:
Poker2009 said:
From what I have read, the ceramic bearing is worse, and replacing a bearing in situ, is very risky and shouldn't really be done unless you have no choice.
Click to expand...

My plan was to fit the EPS Roller bearing when my clutch was due to be changed. I don't like the idea of the LN Ceramic braring. A friend had the LN fitted and it started to fail after 5k miles. He found swarf in the oil filter first so had the Bearing checked as a precaution and found it had begun to destroy itself. The ceramic ball bearings are harder than the steel bearing race and if the bearing was not perfectly aligned when fitted or the car is left standing for long periods, (and the bearing dries up), it can quickly wear out.

As my engine will now be rebuilt by Hartech I'll get them to fit the later IMS with the larger bearing.
Click to expand...

Sorry to hear this! I had mine done at hartech - fully recommend for peace of mind.
One thing to think about.... I sourced a used ims (larger bearing) shaft from eBay and got Grant to fit that - they checked they were happy with it first and they were fine with this solution. I paid something like £250 and they are about £1,000 from Porsche - it was a decent saving.
Other than that I just went with everything else recommended.

Good luck with it!
 
Just for clarity Clanky - a ball bearing does not require a pressure feed (indeed it would not benefit it but overfill the void if ever the seals were good enough to hold a pressure feed).

Ball bearings are designed for either entrapped grease or a small amount of splash oil.

These start out with grease but then due to temperature and the relatively poor sealing qualities of the seals - it gradually gets hot, becomes fluid and runs out of the seal.

If the bearing when fitted was tight or had high spots - initially small particles of worn metal mix with the entrapped grease to form a sort of grinding paste - wearing the whole bearing.

When the grease has run out a very small amount of oil splashes back in - usually sufficient to run the bearing for the rest of the engines life - but sometimes not - hence eventual failure.

If the bearing survives long enough for the seals to wear enough to allow sufficient oil to splash in - then as long as they were not too worn n the initial grease filled stage - they often then last almost indefinitely - hence the general advice - if it has lasted say over 80K probably just remove the seal and leave it alone.

Replacing the bearing in situ can damage the chain, the plastic runner tracks and also result in "pick up" when pressing the bearing into the tight hole that distorts it.

Ceramic bearings do not like shock loading and a view of the "RollRing" video demonstrates the apptly named "clanking" that goes on.

The centre of the bearing remains stationary while it is the outside that rotates - so the centre cannot spin out oil.

The chain sprocket (or gear for a Hivo example) is much bigger diameter than the outside of the bearing and the chain runs up to around 40mph in a chain bath and as a result the forces splashing oil around the proximity of the bearing from those sources well exceed any spin-out from the actually bearing - negating the value of the video you mentioned.

The bearing track retains oil in t he bottom so it is always lubricated on start up and thereafter.

This explains the advice on here to preferably just remove the seal.

If you have to replace it in situ some special tooling can minimise the potential risk of damage.

Baz
 
As there were several different IMS bearings fitted from `98 on are they all suspect for failure from the first design?

*
*
Del.
 
Well put baz; question for you- mines an early 2005 3.8 S with the smaller bearing and it's parked on my driveway which is fairly steep with the nose facing down. Am I right in thinking the ims bearing is swathed in luxurious millers 10w50 nano while it's parked up?

Just a thought and thanks in advance

:thumb:
 
Its submerged in oil when parked on the flat so deffo will be nose down.
 
alex yates said:
Its submerged in oil when parked on the flat so deffo will be nose down.
Click to expand...
:thumb: ssk going in tomorrow bud. Will report back 8)
 
do all cars have these ims bearings, not just Porsche?

I would say yes, if so, its even more of a disgrace that such a basic component was so bollocks.
 
Palladium said:
do all cars have these ims bearings, not just Porsche?

I would say yes, if so, its even more of a disgrace that such a basic component was so bollocks.
Click to expand...

Only porsches flat 6 I believe
 
No they don't. Most have their cams driven off the crank. I thinkthe reason porsche did it was to reduce chain wear, etc. as it can be geared down and run slower, although I always thought it was due to the boxer design flat 6 engine.
 
It also results in a physically smaller cam box sprocket and saves space which is desperately needed when you have two cylinder heads opposed and big tyres to squeeze in.

It reduces the speed of the oil pump as well (although that may not be a good thing).

Ball bearings usually retain oil in the carriers for a long time after running but even if parked up - the ball track in the IMS bearing is a groove internally in the vertical plane so the groove will always have some oil in it whatever way the car is parked and the oil splash is generated before the engine even fires up - so no need to worry about parking angles etc.

Baz
 
Whisper it, but the Mezger had an IMS (in name)

It has to do that the cams are run at the right speed.

The problem with the M96/M97 was yet another cost cutting/production efficiency.

Porsche started with a beautiful and conventional engineering solution, incorporating a continuous clean, fresh, cool oil-fed plane bearing one end, and then the tea-break klaxon sounded, and they popped a (mostly) sealed, greased ball-race not dissimilar to a BMX bike bearing on the other.

Both ends drive symmetric cam systems, both get symmetric oil pressure tensioners, both sides get symmetric forces and torque stresses.

But the bearings aren't symmetric ... and then they wonder why the poor thing imbalances itself to death or simply seizes, cracks or jumps a sprocket and lunches the valves into the pistons when the end with the ball-race overheats or its bearing grease leaks out.
 
Alfaian said:
Well put baz; question for you- mines an early 2005 3.8 S with the smaller bearing and it's parked on my driveway which is fairly steep with the nose facing down. Am I right in thinking the ims bearing is swathed in luxurious millers 10w50 nano while it's parked up?

Just a thought and thanks in advance

:thumb:
Click to expand...

I might start an internet rumour.

You'll know when it's taken, as people will be popping their Porsches in inversion beds at night :bandit:

11822_1000x1000.jpg
 
bazhart said:
It also results in a physically smaller cam box sprocket and saves space which is desperately needed when you have two cylinder heads opposed and big tyres to squeeze in.

It reduces the speed of the oil pump as well (although that may not be a good thing).

Ball bearings usually retain oil in the carriers for a long time after running but even if parked up - the ball track in the IMS bearing is a groove internally in the vertical plane so the groove will always have some oil in it whatever way the car is parked and the oil splash is generated before the engine even fires up - so no need to worry about parking angles etc.


Baz
Click to expand...

Cheers baz :thumb: I can cancel the sleeping tablets for the time being :)

GT4 - behave yourself man :)
 
Palladium said:
so my 1982 has one, why dident they just copy that one?
Click to expand...

As GT4 states - cost cutting.
 
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