2 days ago in Articles
Christina Lam went from the sidelines to full-on track enthusiast in 8 simple steps.
I’m a frugal mechanic. I have a selection of hand tools, a device capable of melting metal together, and a floor jack. I don’t have a lift or special manufacturer’s tools. My workplace will never be featured in “Garage Journal”. In short, I’m typical of most of the GRM “hive”.
Some of us have longed to own a Porsche with the engine in the “proper” position (behind the driver’s seat) but have watched with jaw-dropping amazement as the prices of air-cooled examples have soared to the stratosphere. Well, there are the 986 Boxsters and 996 Carreras – well handling, nice looking enthusiast vehicles. And the prices of Boxsters, especially, seems to be very appealing, with examples from the late 90’s changing hands for well under $8K.
But as most of you know, there’s a reason the buy-in on these cars is so low. It’s the engine, right? The result of an unholy alliance of Porsche engineers and Toyota consultants, the M96 engine has a reputation of failing in numerous and amusing ways. Cylinder bores calve off huge chunks of liner material, which ricochets through the engine causing all sorts of havoc. Intermediate shaft bearings fail and aerosol a mist of iron chips straight to the journal bearings. Most of us know someone who purchased a Boxster or Carrera and paid the dealer or local indy shop the equivalent of the purchase price to keep it running for the first year of ownership.
But how difficult is it really to work on these cars? Could a person with a job, kids, and significant other get one of these cars running reliably without losing all three? Will the price of parts cause heart palpitations?
Well, you’re about to find out. I’ve bought a 2000 Porsche Boxster.
I spent about 3 months on various Porsche enthusiast websites and read the “101 Projects” book cover-to-cover before I started my search. The message boards provide a sobering profile of Boxster ownership: boy buys car….boy hears car making funny noises…..boy finds oil filter covered with metallic debris….boy lists car on Craigslist. Finally, a game plan for angst-free Boxster ownership started to emerge:
Buy a Boxster after getting a reasonable pre-purchase inspection (PPI) Install an upgraded IMS bearing Purchase the Durametric engine software to monitor camshaft deviation angle readings Inspect the filter and have an oil analysis run every oil change Drive and smile
I spent another 4 months searching Craigslist, Autotrader, Cars.com, Bring-A-Trailer, E-bay and a host of other sites. Boxsters in monochromatic hues (grey, silver, black, white) were plentiful and offered the best bargains as they made up about 70% of the cars for sale. The colors I preferred, Guards Red and Speed Yellow, were much harder to find and sold fairly quickly. I inspected a few, drove a few, and learned something new every time. My search started to focus on MY2000 Boxsters. I drove the 3.4 liter “S” model and a car with the base 2.7 liter engine back-to-back and decided that I could live with the smaller engine. MY2000 was the last year Boxsters were manufactured with the “double-row” IMS bearing which had a lower failure rate than the “single-row” bearing used in later years. Porsche also seemed to have gotten a handle on the “d-chunk” cylinder lining failure after 1999. In theory, there was also a much larger pool of replacement engines available, should my car die from my ham-fisted frugal mechanic maintenance.
Finally, I found this:
A Speed Yellow base (2.7 liter) with around 100,000 miles on it. A 2000 model year, so there was a good chance it had the “double row” IMS bearing which had a significantly lower failure rate. I called and found the owner was out of town, however I could inspect but couldn’t drive the car. After a minute of deliberation, I hopped in the car and made the 9 hour round trip to check it out. Nice car. Paint was glossy and the interior reflected respectful ownership. The Carfax recorded two previous owners and showed evidence of mostly preventative maintenance at the local Porsche dealership. I wriggled under the car and found evidence of a leaky rear main seal for a potential bargaining chip.
A nearby import shop did the PPI. Found evidence of recent brakes, water pump and air-oil separator. The oil filter was removed and cut open with no evidence of metal bits or plastic from the timing chain wear paddles. Camshaft deviation readings for both banks were below 6% and steady. These observations indicated the IMS bearing was still intact and the engine serial number indicated that the engine left the factory in late 1999 and was probably equipped with the double-row IMS bearing. The engine emitted a short rattle for a second when started cold. It could be a sticking tensioner, or it could be worn pads on the Variomatic solenoids (a job best done with the engine out). Did I feel lucky?
I paid $7500. A bit on the high side, but I was willing to pay a little extra for the nice condition. Like a lot of manufacturers in the 90’s, Porsche used “soft surface” coatings on most of their interiors and many of the Boxsters I’d inspected were scratched, peeling messes. And since I planned to perform the clutch, IMS bearing, and rear main seal replacement all by myself, I would be saving the $3K to $5K a dealer or independent shop would charge for this work.
My flight to Wilmington, North Carolina on the following weekend had a crazy fast gate change in Charlotte, so bringing my rescue tool bag as checked luggage wasn’t an option. Consequently, I started the long drive back with only the Bentley manual for my Boxster and a AAA card for roadside assistance.
The drive between Wilmington and Augusta, GA is pretty boring, except for signs for Pedro's South of the Border every 5 miles.
No worries, as my new vehicle traveled the 300 miles with nary a hiccup. Arriving at the house, I gave SWMBO a short drive to show off my new car, as it would soon be rendered inoperable - perhaps permanently.
I’d started ordering parts as soon as the deal closed and was pleasantly surprised at the relatively low cost. A Sachs clutch kit with throwout bearing, pivot bearing and clutch tool was $300 from the Ebay shop of a well-regarded internet vendor. The rear main seal was $16 and I spent around $20 to replace all the torque-to-yield bolts Porsche uses on the flywheel, clutch plate and CV joints.
Trying to decide on the upgrade path for the IMS bearing was an ordeal for me. Poke around the Boxster and 996 internet forums and you’ll find every discussion of this topic invariably degrades into an ugly flame war. Porsche delivered the M96 engine in over 120,000 Boxsters (and a similar number of 911s) to a customer base not known for flinching at $3000 repair bills. As a result, there’s a lucrative market for IMS bearing replacement options. Parts prices range from around $250 for a like-for-like replacement to over $2000 for an upgraded bearing with a dedicated oil feed. The type of IMS “fix” is a deeply-held core value among Porsche enthusiasts. Having spent upwards of $4000 to make this problem go away, they will argue rabidly and vociferously with anyone championing an alternative. The “fix” I eventually selected cost around $400, and won’t be mentioned by name, lest outside observers descend and cause this thread to descend into anarchy. Attentive readers will recognize it from the photos, anyway. Others have selected other options, and I look forward to reading their build diaries.
Two weeks after I brought it home, I started with the IMS bearing replacement. First step is to create enough room under the vehicle to work comfortably. Putting the Boxster on jack stands is a simple matter. In back, a triangular reinforcement plate provides a jacking point to install the stands at the lift points in front of the rear wheels. In front, the jack can be placed on a box beam on each side of the vehicle to install the stands at the lift points behind the front wheels. With the lift points 15 inches off the floor, my 6 foot frame could sit comfortably upright at the business end of the engine.
I removed the rear bumper and support. It’s not a requirement, but it makes removing the muffler and exhaust much easier. And if you don’t, you’ll whack your dang head on it every time you duck under the car. You will be ducking under the car…a lot. One of the endearing (but kinda useless) features of the Boxster is a rear wing which pops up from the car when it reaches 70 mph. I’d been warned that the socket head bolts which hold this retractable wing to the actuating solenoids have the yield strength of unpasteurized cheese, so I made sure my allen socket was set in the bolt head by giving it a good whack with a hammer before untorquing. Even so, removal still stripped them and I sourced stronger replacements from the local hardware store. With the retractable wing removed, you can access the screws for the bumper cover. The bumper cover goes into a safe storage area and the supporting bracket forms the base of the pile of parts that will soon fill the corner of your garage.
Removing the large triangular aluminum support plate and a pair of brackets opens up access to everything you need to remove. Exhaust system is first.
This porky muffler and attached “post” catalytic converters weighs nearly a hundred pounds. Most Boxster owners ditch it in favor of something lighter with a better exhaust note. Will probably be my Christmas present this year. In preparing for this job, I scoured and copied about a half dozen IMS replacement blogs from the interwebs. I was always dumbfounded when folks reported that it took about three hours to remove this pig – but never explained why. Here’s why: when you unbolt the exhaust flanges up by the engine, you’ll find the nuts on the most inaccessible flange corners are welded to speed up assembly at the factory. Deez nuts are low strength carbon steel, and after 100,000 miles are now only nut-shaped piles of iron oxide; hopelessly seized to the inserted bolts. But worse, the weld metal used to fasten these nuts is about 3 times stronger than the nuts, which makes it a real chore to cut/ground/chisel it away. Did I mention that the flanges are next to the cylinder head thereby maximizing collateral damage from a slipped tool? Fortunately, years of tackling home improvement jobs clearly outside my abilities have given me the ability to wield a Skill Saw as deftly as a surgeon or a union meat-cutter. I chucked a bi-metallic blade in, murmured a prayer, and went to town. When things finally yielded, I glanced at my watch as I wiped the sweat from my brow. Yeah, took about 3 hours.
Other than that, removing everything for access to the transmission bolts was straightforward and actually enjoyable. Every nut had plenty of access for a breaker bar. Every brace and bracket was arranged for removal in sequential order, just like the engineers knew that the clutch would be accessed in a track environment.
With the exhaust out, the bolts for the CV joints are removed and you’re staring at a transmission sticking out of the back of a 6 cylinder engine. Every transmission bolt pretty much accessible. After my experiences with replacing clutches in Miatas, I thought I had died and gone to heaven. Couple of things left to do. First, we remove the clutch slave on the driver’s side of the engine. Just unbolt it and it hangs out of the way.
And next, the linkages for the cable shifter used in the Boxster. It’s easier to just leave all the ball joints connected. Remove two bolts to release a bracket and unscrew a setscrew and the whole mess – cables, linkages and all just tucks to the side. Several of these plastic ball joint ends are integral to the shifter cables, which cost around $500 to replace. I wasn’t too keen on trying to pry everything apart and breaking something.
I put my ancient trolley jack under the oil pan to provide a little more support for the engine. Unbolted the transmission mounts (found them to be in good shape) and the transmission was ready to be pulled.
After researching a dozen IMS replacement threads on the various Porsche boards, I’d been warned that there was ONE freaky bolt on the transmission housing (there’s always one, isn’t there?). It has the triple-square head, beloved of Porsche and VAG designers and the transmission housing prevents you from getting a straight shot at it. I took a 10 mm triple-square bit, left over from a regretful period of ownership of a Mark IV Jetta, and went to work with an angle grinder. Yay! My first Porsche special tool – so proud.
Only have access to get a box-head wrench on it, and I was too lazy to get a cheater bar. So, in true redneck fashion I daisy-chained another box end on it and it screwed right out.
The rest of the transmission bolts were easy to access. The one at the top is supposed to be easier to reach by removing the engine cover and pulling the air inlet pipe, but I was on a roll and linked together a couple of extenders so I didn’t have to crawl out from underneath the car.
Not a huge fan of the Harbor Freight transmission jack, as its only adjustable fore-and-aft. Really wish they still sold the transmission adaptor that bolts to their heavy-duty jacks. A little bit of persuasion and the transmission separated cleanly.
In my next installment, we’ll get our first look at the unholy IMS bearing. Thanks for listening.
An entertaining start to what I'm sure will be a great story! Love the car and the plan. Also it's good to know there is a Porsche out there I can afford....
Great thread - I'll be following intently!
Terrific start. I can't wait to read more.
really enjoying this so far. keep it coming!
Very cool. I can't say I've seen another DIY IMS bearing replacement thread before. I'll be watching with some interest.
I put a billyboat exhaust on mine at only four years old and all those bolts were the same way. Nice write up, I'm subscribed!
Thanks for the kind responses! More on the way. Just taking a while to figure out the syntax and the easiest way to drop pics in from my Photobucket account.
Keep up the great work, from all of us without the guts to face off with the porsche we can afford.
mrap1000 wrote: Thanks for the kind responses! More on the way. Just taking a while to figure out the syntax and the easiest way to drop pics in from my Photobucket account.
Easiest way is to right click on the HTML link on Photobucket and just paste it directly into the text of your thread. No need to click any of the link buttons on top.
Definitely following this one. I keep hearing a Cayman calling my name. Someday I'll have to answer.
First, an homage. I’ve been lurking on this board for around 10 years and I hold the Dorks, UltraDorks and MegaDorks in near-reverence. I never thought I’d do anything “interesting” enough to post here. My interest in the Boxster was piqued by Maroon92’s “Project Boxster” thread back in 2014. I started researching the car and the various reliability challenges of the M96 engine and finally pulled the trigger. Maybe this thread will help others, who might be considering the Boxster as a DD or autocross weapon. Maybe this thread will cause others to back away slowly, murmuring “nope, nope, nope”. Anyway, here’s the obligatory “pile of parts” in my garage:
Now it gets interesting, because we’re getting closer to determining the true condition of the IMS bearing. Has it spun smoothly for the last hundred thousand miles or has it broke bad and spewed a stream of metallic flakes into my oil system? I’ve read more than one IMS replacement thread where the owner cheerily describes the disassembly sequence, pulls the bearing, and finds this (not mine):
See that grey puree of fine metallic particulate on the seal area? That’s nightmare fuel for a Boxster owner. This bearing probably spun just fine, but has completely contaminated the oil system. The oil passages in the Boxster’s M96 engine are on the small side, as is the overall capacity of the oil pump. It doesn’t take much of this stuff to wipe a cam or main bearing. Although there are some who believe a contaminated engine can be made whole by dropping and cleaning the oil pan and doing 500 mile filter changes with a low viscosity oil, prevailing wisdom is you’ll only find peace with a complete engine disassembly and ultrasonic cleaning of parts.
Quick tip if you’re shopping for a Boxster. If the Craigslist ad includes the phrase “recent oil change with synthetic”. It means the owner found this on the filter, and his hoping there’s some magic elixir in Mobil 1 that will keep the engine running long enough to unload it.
So, we remove the bolts holding the pressure plate assembly to the flywheel.
And we get our first look at the clutch disk. The friction material on the flywheel side doesn’t look bad.
The other side, not so much. We’re down to the friction pad rivets, here.
The pre-purchase inspection found no evidence of clutch slippage and it drove just fine. However, the import shop technician noted that the pedal required a bit more force to fully depress, which usually indicates the clutch is on its way out. Anxious to get my first look at the IMS bearing cover, I restrained the flywheel with a heavy-duty tie-wrap and cracked the flywheel bolts loose. Yippee, more TTY bolts with the consistency of stinky cheese. These bolts are torqued to 19 ft-lbs AND then another 120 degrees during assembly, so they are tight. Most mechanics just grind them off with an angle grinder, but I took it as a challenge. Tapped in the Torx socket with a hammer to get it seated, bear down on my 4’ breaker bar, and SNAP – I fractured my fine Chinese-manufactured socket right in half. Back to the hardware store to purchase something a little more robust. Eventually, they yielded and I was greeted with this:
Well on the negative side, I do have a rear main seal leak. The weeping oil has been mixing with clutch dust and formed a lovely cake on the back of the engine. On the positive, there’s no apparent leakage in the IMS bearing area. The stud passing through the bearing from the engine side can fracture and cause an oil leak in this area. Closer inspection shows the bearing cover has a “shallow” dimple around the stud, which means the more reliable double-row bearing was installed at the factory. Things are looking up.
Now, before I can proceed, I have to remove the pre-tension on the five timing chains and lock them in position. That way, when I remove the IMS bearing for replacement, the whole assembly won’t jump time. The M96 timing system looks like this:
The IMS bearing supports radial loads on the sprocket marked “3” and when it’s removed, this whole mess has a tendency to shift. To keep that to a minimum, we’re going to remove the Tensioner marked “4” and the unmarked vertical one to the left. This will remove most of the preload on the chain. Finally, to keep any spring load on the cams from pulling things out of whack, we’ll pin the crankshaft pulley “2” and restrain one of the cams on the left side of the picture. When we reinstall the new bearing and tensioners, everything should restore to the original timing positions when we remove the locking tools.
You can purchase the IMS tool kits on Ebay for $150 - $200 and sell them for a similar value when finished. I opted to rent the tool kit from an online Porsche parts place. The kit has the special tool which pulls the IMS bearing out of the shaft and a pair of tools to lock down the timing. To lock down the timing, you push the seats forward and remove the carpeted firewall insulation panel and hatch cover to access the front of the engine. Porsche does a great job of marking TDC with markings cast on the engine casing. One timing lock tool slips through a hole in the crankshaft pulley into cast recess in the engine casing like so.
The second tool locks the camshafts in place. The hatch firewall hatch provides access to the camshaft ends for cylinder bank 1-3. On a 5-chain timing system like mine, the lower (exhaust) cam has a locking slot on it. Popping off a plastic cover provides access to the end of the cam, and the second locking tool slips into the cam slot. The other end bolts to a boss on the engine casing to prevent the cam from rotating.
Now we can remove the tensioners. My hands were shaking a bit at this stage and my photos are a little blurry. Here’s a good photo from Pelican Parts. Here we remove tensioner “4”:
And here’s the other tensioner removed:
Back underneath the car, we stick a screwdriver into the IMS shaft and loosen the locking bolt. Now we can actually rotate the IMS bearing to evaluate its true condition. Wiggle it. Any play in the shaft? No? Good. Rotate it. Does it rotate smoothly with no evidence of roughness? No? Good, now get down on your knees and offer a prayer of thanks to the God of your understanding.
The bearing puller is pretty simple. It’s a cylinder which braces against a lip on the engine casing. A threaded rod is attached to the IMS bearing stud and torque is applied to pull the bearing out of the engine casing and into the cylinder.
Not mine, but here’s a picture of the puller in action:
There was some wincing, straining, and murmured oaths. Finally, this popped out.
The bearing in my Boxster was a Japanese-made NSK bearing. And it was pretty much perfect. Didn’t have a lick of grease in it, anymore. Just sat on an absorbent towel and leaked for a few days. Like everyone else, my hollow IMS shaft was about 25% filled with nasty, smelly, burnt-out oil which had migrated into the shaft over 100,000 miles of operation. I cleaned out the inside of the IMS shaft and readied my new bearing for installation.
It’s an interference fit, so I’d stuck the bearing and attached stud into my freezer two days before. I used a heat gun to warm the IMS shaft up to 180 degrees F:
And with the new IMS bearing loaded into an installation tool, tapped it into its new home.
Next, we'll move to replacing the rear main seal and putting humpty dumpty back together again.
I'm really enjoying this. Good job!
You're doing a great job demystifying the whole IMS replacement for me. Great job! Is it me, or does it look a bit off center in the last pic? Does it straighten out when the tension is returned to the chains?
In reply to 4Msfam:
Good observation. The alignment of the IMS shaft is maintained by the cover plate (the circular one with the three bolt holes). When the cover is removed, the shaft drops down and to the side in the engine sump. It returns to alignment when the cover is re-installed. That's why it's so critical to lock the cam and crankshaft sprockets and remove any force on the chains from the tensioners before removing the cover. Otherwise, tensioner force yanks chains, and sprockets jump teeth as the cover is removed.
Good job with everything. Except the exhaust part this really doesn't sound like too bad of a job if it's a toy and don't need it to go to work on Monday. It all seems pretty straight forward.
If the clutch pedal was heavy check the shaft on the trans that the throw-out bearing slides on, it or the carrier is likely worn. After I had my clutch replaced, IMS bearing replaced, new throw out bearing carrier and sleeve to fix the shaft it slides on, my clutch is as light as any other newish car. When I first got My Boxster the clutch was extremely heavy, enough that driving in traffic was something I avoided if I could.
mrap1000 wrote: The engine emitted a short rattle for a second when started cold. It could be a sticking tensioner, or it could be worn pads on the Variomatic solenoids (a job best done with the engine out). Did I feel lucky?
Have you gotten into this issue at all yet? My 996 does this, after it has been sitting for a day.
GREAT thread! The pictures and explanation are very helpful. keep it up!
Great thread, and relevant to my interests as I am really tempted by cheap Boxsters from the years afflicted but haven't really researched the issue much yet.
One question - it looks like you just removed the factory IMS bearing and replaced it with one of a different design. Is that really all there is too it? Was the original bearing just too small or poorly spec'd? I guess I was expecting there to be some sort of modification of the bearing's lubrication, etc. Or is that coming in a future installment?
I'll add my voice to the praise for this thread. You have the right attitude, and your well informed approach is dead on.
In reply to Devilsolsi:
I've replaced the tensioner for the IMS shaft to Crankshaft chain. Didn't fix it. Will be doing the Variomatic tensioners in the near future.
In reply to SEADave:
Great comment! I'll cover some of the bearing replacement and lubrication options in my next thread.
And yes, changing the IMS bearing is pretty easy. Only adds maybe two hours to a clutch change.
In reply to mrap1000:
Check the oil filter for plastic debris, too. I've had that particular rattle on my 996 and that turned into a full engine stripdown due to the plastic pads for the chain tensioners wearing and falling apart.
BTW, check for the rattle with the a/c turned off. In really hot weather I get a very similar knock from the a/c kicking in.
In reply to BoxheadTim:
I've read your 996 odyssey many times and it's been a great source of inspiration. Did an oil filter check during PPI and I did another when I drained the sump before starting this job. No brown or black plastic (yet). Internet experience shows that a Variomatic pad, chain replacement and replacing the remaining tensioners should fix the rattle in the future. Still trying to research how to do this with the engine in place.
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