Can an IMS be avoided?

[AddictionRacing]

Originally Posted by chitowndad

So what's the difference between the RMS and IMS? I'm familiar with the RMS (Rear Main Seal) which I believe is on the block behind the cams, correct? What exactly is the IMS and when it fails why do you have to replace the entire engine?

Thanks,

-Steve

The IMS is the intermediate shaft. Unlike RMS it's not a seal. My very basic understanding is that there is a ball bearing in the intermediate shaft that fails and as it fails it comes apart in tiny pieces of metal that you'll later find in your oil and oil filter. Some, like mine, are detected while the car still runs and theoretically you should be able to tear down the motor, replace the bearing and shaft, rebuild, and go on your merry way, but Porsche does not manufacture the replacement parts necessary. Porsche knows they messed up designing it and does not manufacture the identical bottom end any more. They've since upgraded to a larger bearing, which should be better. I hope this helps, and I'm sure others will chime in.

[Lil bastard]

The IMS drives the chains (2) which powers the camshafts (4). The bearing can fail outright, as mentioned, metal bits in the lube circuit, failed timing, etc.

But, it can also fail progressively allowing some flex to the shaft and it's chain sprockets. This flex imparts inconsistent tension on the chains which can then slip a few teeth on the sprockets. This throws off the mechanical timing creating poor running and/or allowing the valves on this 'interference' engine to 'shake hands' with the pistons and it's "Sayonara Motorsan!!"

The funny part is, this IMS issue started after Porsche redesigned the system after '02 to eliminate supposed vibration issues (and IMHO, make way for Variocam Plus). IMS is extremely uncommon on the earlier models, which are more prone to RMS failure due to their early generation seals.

[Brucelee]

Hey, Porsche said they were sorry!