CBR944

AnthonyGS was referring to the intermediate shaft itself, which has the gears at each end press-fitted. Apparently, the gears have been known to slip on the shaft, which affects timing on one or both camshafts (potentially enough to cause major damage). I have no idea of the extent of actual risk, though, or how often this might have actually been known to occur. I would guess it's rare, as almost never seems to be attributed to engine failure in 986s or 996s. Anyway, "pinning" the gears to the shaft prevents this occurring, but requires major engine disassembly.

David

996AE

IMSS gear slip failure CNN HEADLINE NEWS

Lighting strike at bottom of dry pool

Sounds like an oil thread

Starter986

What oil are you using? And why?

Skitch

I've switched to a nice zero weight canola oil, big power gains!

But seriously, I think what he might be referring to is doing the IMS replacement without locking out the cam chains, I think I have seen some youtube videos where that has been the case. It certainly would be possible to screw up the timing!

Tim

Jack-Porsche

All due respect, stupidity would be paying $20,000 for a blown motor when the car can be replaced for less than that.
If someone can do the IMS themselves, go for it, but otherwise at the stage of the game we are in with the 986, doing nothing (Drive your car and change oil regularly) is likely the most sensible in my opinion.
From my research, a ~20 year old car that has been regularly driven and maintained continues to be less likely to have an IMS bearing failure. Even using the original failure rates, the overwhelming odds are that it WON’T fail.
Stupidity is spending several thousand on a replacement bearing as preventative maintenance on a car that is only worth several thousand at this point.
I say...enjoy the market stupidity that currently allows us to buy these old 986 for less than the cost of a nice vacation. Drive the hell out of it, and get another if it fails.
The perceived “cost of Porsche ownership” is what keeps many away, which is just fine with me (more for us), but in large part it’s a thought shared by people who know nothing about Porsche.
All just my opinion

HenryPcar

I wouldn't invest that kind of money into a Boxster.

ZuffenZeus

Yea, I totally get your point, man. I've heard many times that 986 cars are considered disposable because of depreciation vs. cost of engine rebuilds, maintenance, repairs, etc. Regardless, if you have a base Boxster or special edition (like in the video below), you really must "love" the car if you want to fork out north of $20K keeping it alive.

SandyG

Consider the LNE "IMS Retrofit" instead of the "IMS Solution." The Retrofit kit is $1,000 less, and my mechanic didn't like the exposed oil line on the Solution, either. He quoted $3,000 for the Retrofit + clutch + RMS for my 2000 BS manual. There's more labor for the Tiptronic, as they are more work to remove it to get to the clutch and IMS bearing.

Mark Dreyer

I drove my 986 S many miles on track without an upgraded IMS. When I did the transmission rebuild, I went ahead with the fix and was told my original bearings were pristine. Prior to this fix I had found a spare engine from a fellow RLer for around $3k which collected dust for several years before I finally sold the car, the engine still running like brand new. My point is I wouldn’t pay $8k for the IMS. Drive it like you stole it and if/when the engine blows, you can find an entire engine for way less than $8k.

mikefocke

Was the quote in any way itemized? In writing? Reason I asked is a year ago I had an insurance claim denied and after a lot of digging found out that the contractor had honestly made a mistake that amounted to thousands. He just slipped a digit in inadvertently in the quote he sent to the insurer.

While Porsche mechanics are expensive (and good ones doubly so) location can have an effect on the rates too.

sebastiandauod1

I recently had bought one of the lowest milage boxsters in the US, in may of 2019 paid 12400 for the vehicle with 24500 miles, 04 base red with black interior. My IMS went 2 years later at 39k miles. Destroyed my entire motor, I had to find now a newer 03 04 motor 2.7 with reasonable mileage to match my low mile chassis. I got an entire motor assembly with 66k miles for 4800 and while in there I did a clutch kit with throw-out bearing and the LN IMS solution kit along with this the air oil separator and practically every gasket in the top end of the motor. My bill for labor of a new engine install clutch install ims bearing install and everything was 3970 out the door with tax. ALL IN ALL FOR A MOTOR CLUTCH IMS WAS 8800 AND I GET TOO KEEP MY CORE.

Flat6 Innovations

The value of the car is does not indicate the cost of ownership, or procedures. It costs the same to carry the work out on a 2007 997.1S as it does to carry the work out to a Boxster worth 1/3 the amount of money. Both engines also cost the same to reconstruct, despite the vehicle value. 8K or so is what we also charge for an IMSS retrofit preventative package.

Mode of failure #24

Shawn Stanford

This is why I wouldn't even look at a first gen Boxster with under 100k on the clock.

ChuckUFarley

It happens...I just got done with a full rebuild on my '99 C4 over the past few months going from 3.4 to 3.8 Nickies, and last Sunday 7/9 started it up for the first time. It ran great for about 7 minutes, then suddenly ran extremely roughly. Shut it down immediately. After pulling the cam plugs on both banks and rotating by hand, I found that Bank 2 cams were rotating as expected but Bank 1 were not. During the rebuild I pinned the main sprocket but did not weld or pin the two smaller sprockets that connect to the exhaust cams. I strongly suspect that the Bank 1 sprocket (the one right next to the large sprocket as shown in Raby's video above) has come loose and is not turning with the shaft. One hell of a gut punch after the amount of work that went into this, but at this point I know my way around the engine enough that it should go much easier this time around.
The somewhat misleading part was that the Bank 1 cams (the side that does not move) came to rest at exactly where they should be for Cyl 1 TDC, which was highly confusing for a few minutes until I watched the Bank 1 exhaust cam for rotation while turning (and they didn't move at all). I wonder if the pistons "helped" to turn the valvetrain back to TDC position for the few rotations...by pushing back against the valves. Ugh. Should be interesting to see all of the collateral damage once I start pulling it apart.
Pin or weld your sprockets, people!
Pin in main sprocket: