the Porsche 986/996 IMS bearing "issue"

lemming · 12-18-2014, 10:48 AM

in case anyone has been following the Jalopnik "cheapest Porsche ever" buying guide or the subsequent "best Porsche under 30,000USD" thread, this may or may not be of interest.

I have not personally come across any vehicles that have suffered an IMS bearing failure --but i have run across many cars that have pre-emptively replaced the part as both insurance as well as to prop up resale value.

the issue is that the intermediate shaft which runs north/south through the engine pan, whereas in the past was anchored by an "open" rotating bearing (ball bearings) that swam in a sea of oil, in the M96 motors, they changed it to a closed bearing design (who knows why). this means that if the seal which holds the grease in that self-contained bearing fails, the bearings lose lubrication and the bearing fails. pretty straightforward. the bearing failure tends to show up early --or-- on cars that are not driven often. Early means some OEM related failure (rare). Late failure can be attributed to low miles and cars sitting (not driven) or infrequent oil changes --if the oil is dirty, at some level when contaminated with fuel and whatnot, it will accelerate degradation of the seals on the bearing. Overall fail rate tracks closely with years (2000 to 2002 being apparently the worst) with an overall fail rate of maybe <5%?

long story short, I have my not superbly maintained car (with 50,000 city miles) on it serviced. the IMS bearing was fine. naturally, having the tranny dropped to put in a new clutch, it would be obtuse to not checkout the IMS bearing, so that's what happened. if anything, the OEM dual mass flywheel was in bad shape and needed immediate replacement.

my advice? don't worry so much if you are driving the car. look at the IMS bearing (if your car has over 30,000miles) as a wear and tear item that piggyback's onto the labor costs of a new clutch.

the really scary things are the water pump (overheating potential), the air oil separator (AOS), the crappy ass OEM flywheel, of the radiator plumbing.

i'll post pictures tomorrow. i have all of the original parts held for me. i'm not thrilled about the out of pocket, but I negotiated intensely so overall, I feel that for a one owner car, I did okay.

12-18-2014, 10:48 AM	#1
lemming Western Anomaly Join Date: Oct 2003 Carmudgeonly Ride: White Orca Posts: 16,659	the Porsche 986/996 IMS bearing "issue" in case anyone has been following the Jalopnik "cheapest Porsche ever" buying guide or the subsequent "best Porsche under 30,000USD" thread, this may or may not be of interest. I have not personally come across any vehicles that have suffered an IMS bearing failure --but i have run across many cars that have pre-emptively replaced the part as both insurance as well as to prop up resale value. the issue is that the intermediate shaft which runs north/south through the engine pan, whereas in the past was anchored by an "open" rotating bearing (ball bearings) that swam in a sea of oil, in the M96 motors, they changed it to a closed bearing design (who knows why). this means that if the seal which holds the grease in that self-contained bearing fails, the bearings lose lubrication and the bearing fails. pretty straightforward. the bearing failure tends to show up early --or-- on cars that are not driven often. Early means some OEM related failure (rare). Late failure can be attributed to low miles and cars sitting (not driven) or infrequent oil changes --if the oil is dirty, at some level when contaminated with fuel and whatnot, it will accelerate degradation of the seals on the bearing. Overall fail rate tracks closely with years (2000 to 2002 being apparently the worst) with an overall fail rate of maybe <5%? long story short, I have my not superbly maintained car (with 50,000 city miles) on it serviced. the IMS bearing was fine. naturally, having the tranny dropped to put in a new clutch, it would be obtuse to not checkout the IMS bearing, so that's what happened. if anything, the OEM dual mass flywheel was in bad shape and needed immediate replacement. my advice? don't worry so much if you are driving the car. look at the IMS bearing (if your car has over 30,000miles) as a wear and tear item that piggyback's onto the labor costs of a new clutch. the really scary things are the water pump (overheating potential), the air oil separator (AOS), the crappy ass OEM flywheel, of the radiator plumbing. i'll post pictures tomorrow. i have all of the original parts held for me. i'm not thrilled about the out of pocket, but I negotiated intensely so overall, I feel that for a one owner car, I did okay. __________________