The IMS bearing fails mainly because it is a sealed ball bearing at the end of the intermediate shaft, and it often does not get the kind of continuous lubrication and support a long-life engine bearing normally needs. Over time, the grease seal can age, lubrication can degrade, loads and heat can wear the bearing, and once it starts to loosen or shed debris, failure can cascade into major engine damage.
In my case, I purchased the car 2 year ago with 35k miles on it. As its a 2003 car, its easy to assume the car was not driven frequently. Long periods of sitting can be hard on the bearing.
Engine Removal:
1. Put the car safely on a lift or sturdy jack stands.
2. Disconnect the battery.
3. Drain oil and coolant.
4. Remove the rear bumper cover, muffler/exhaust, and underbody panels for access.
5. Remove intake parts, airbox, and related hoses.
6. Disconnect the main engine harness, grounds, and any remaining electrical plugs.
7. Disconnect fuel lines, coolant hoses, vacuum lines, and power steering connections as needed.
8. Remove both drive axles from the transmission.
9. Disconnect the shift cables and clutch slave cylinder line.
10. Support the engine/transmission with a jack or engine support.
11. Remove the transmission brace, rear mount hardware, and bellhousing/support bolts.
12. Lower the drivetrain carefully and slide it out from under the car.
I found a 2003 Boxster S M96.24 Engine with 80k miles for a replacement.
Engine Inspection - rented a boroscope, inspected the cylendars for scoring. Inspected from the spark plug holes, and from the bottom though the oil pan.
I used this kit: Pelican Parts IMS Retrofit Kit. There is a proceedure for that kit here.
1. Remove the engine or at least separate the transmission from the engine.
2. Rotate the engine to cylinder #1 top dead center and lock the crankshaft in place.
3. Lock the camshafts and remove the chain tensioners as required.
4. Remove the IMS flange and extract the original bearing.
5. Install the new bearing, support hardware, and any supplied plug/seal pieces.
6. Install the new flange or cover with thread sealant where required.
7. Refit the transmission, refill fluids, and confirm timing and operation.
1. Confirm the engine and transmission are fully assembled, with the clutch, flywheel, starter, mounts, hoses, and wiring already attached where needed.
2. Put the car in service position, raise the rear safely, and keep the drivetrain on a transmission jack or sturdy rolling support.
3. Roll the engine/transmission assembly under the car and align it with the chassis openings.
4. Lift it slowly into place, watching the exhaust tunnel, coolant lines, axle areas, and rear bodywork for clearance.
5. Start the main mounting bolts by hand before tightening anything fully.
6. Reconnect the transmission mount, rear support bracket, and engine mount hardware.
7. Reinstall the axle shafts, shift cables, clutch line, and any transmission linkage.
8. Reconnect all coolant hoses, fuel lines, vacuum lines, electrical plugs, and ground straps.
9. Reinstall the exhaust, heat shields, intake parts, and undertrays.
10. Refit the bumper and lower covers.
11. Refill oil and coolant.
12. Reconnect the battery and test for leaks, warning lights, proper shifting, and normal idle before road testing.
Bla Bla Bla