IMS bearing installation - a new owner's retrospective

[Dennis Nicholls]

I started quite a few topics asking for advice during my LN IMS bearing installation.  I'll let those threads die now and make comments in this retrospective thread.  Thanks to all who helped out and a special thanks to John in Penn.  My comments relate specifically to a MY 2000 base 986 with 5 speed MT.

 

The job is pretty much at the end of endurance for an older (age 61) home mechanic.  There's lots of pushing and shoving to get the job done and I don't have the strength I did years ago.  I've been working on cars since circa 1970 and have become proficient at Miata work since 1994. 

 

Tools are important and the Bentley guide/Dempsey's book are not clear about this.  I bought the HF tranny jack which did yeoman service with both the tranny and the muffler.  The Neiko triple square set is a good choice, as it has a short M10 for that oddball tranny bolt and a tamper proof M16 for the tranny drain plug.  Get a long 10mm box wrench to wrap around the M10 to break/make torque.  I got a set of impact rated Lisle Torx bits from Sears on sale for $20:  the T55 bit had no problem with those use-once bolts on the flywheel.  You need a good long 6mm allen wrench bit for the inner CV joint bolts.  A short one goes in crooked due to the rubber CV boots.  HF has a set of 4.5" long allen bits that did the trick for me.  A cheap 17mm allen bit for the tranny fill plug is adequate as it's not torqued tight. 

 

John said a 3 lb. dead blow hammer was about the right weight.  Get clean cotton gardener's gloves to hold the frozen LN IMS bearing and installation tool when you pull it our of the freezer. 

 

To drive the RMS you need a nominal 4" OD PVC pipe coupler.  But you can't ask for a 4" coupler since this size is actually called a "3 inch coupler" since it couples pipe of ID 3".  There are two kinds, schedule 40 and schedule 80, and you want the bigger of the two.  Get silicone grease from your plumbing supply as it can be used to lube the o-ring in the LN flange.  A thin smear on the rubber jacket of the clutch slave also helps shove it back into place.

 

 

[JFP in PA]

I started quite a few topics asking for advice during my LN IMS bearing installation.  I'll let those threads die now and make comments in this retrospective thread.  Thanks to all who helped out and a special thanks to John in Penn.  My comments relate specifically to a MY 2000 base 986 with 5 speed MT.

 

The job is pretty much at the end of endurance for an older (age 61) home mechanic.  There's lots of pushing and shoving to get the job done and I don't have the strength I did years ago.  I've been working on cars since circa 1970 and have become proficient at Miata work since 1994. 

 

Tools are important and the Bentley guide/Dempsey's book are not clear about this.  I bought the HF tranny jack which did yeoman service with both the tranny and the muffler.  The Neiko triple square set is a good choice, as it has a short M10 for that oddball tranny bolt and a tamper proof M16 for the tranny drain plug.  Get a long 10mm box wrench to wrap around the M10 to break/make torque.  I got a set of impact rated Lisle Torx bits from Sears on sale for $20:  the T55 bit had no problem with those use-once bolts on the flywheel.  You need a good long 6mm allen wrench bit for the inner CV joint bolts.  A short one goes in crooked due to the rubber CV boots.  HF has a set of 4.5" long allen bits that did the trick for me.  A cheap 17mm allen bit for the tranny fill plug is adequate as it's not torqued tight. 

 

John said a 3 lb. dead blow hammer was about the right weight.  Get clean cotton gardener's gloves to hold the frozen LN IMS bearing and installation tool when you pull it our of the freezer. 

 

To drive the RMS you need a nominal 4" OD PVC pipe coupler.  But you can't ask for a 4" coupler since this size is actually called a "3 inch coupler" since it couples pipe of ID 3".  There are two kinds, schedule 40 and schedule 80, and you want the bigger of the two.  Get silicone grease from your plumbing supply as it can be used to lube the o-ring in the LN flange.  A thin smear on the rubber jacket of the clutch slave also helps shove it back into place.

 

I'll bet you are glad it is all done, now enjoy those summer roads.................. :thumbup:

[Dennis Nicholls]

My first challenge was getting the muffler off.  Most instructions says something like "remove muffler".  Not very helpful.

 

You need to take off the two U shaped pipes that connect the muffler to the two main cat cons.  They are held on with a 1-bolt clamp at the muffler and a 2-bolt clamp at the cat con.  Slacken the 2-bolt clamp at the cat con.  Slide it back towards the cat con.  It will expose the "butt splice" where the U pipe meets the cat con pipe with a small gap.  Now slacken the 1-bolt clamp.  That end of the U pipe is slid about 2" inside the muffler pipe, and being able to rotate the pipe lets you gradually withdraw the U pipe from the joint.  Once both U pipes are removed it's not difficult to disconnect the rest of the muffler and lower it with the help of the HF tranny jack.

 

Summary:  2-bolt clamp covers a butt splice;  1-bolt clamp covers a slip joint.

[Dennis Nicholls]

The tranny comes off fairly easily.  Just remember to use a LONG 6mm allen bit to undo the inner CV joint bolts.  When lowered on the HF tranny jack, the tall part of the tranny slips out under the tailpipe cutout in the rear bumper.

 

You need to hold the flywheel from turning when removing/installing the 8 T55-head flywheel bolts.  Most people use some kind of metal bracket between a bellhousing bolt and a pressure plate bolt.  Unfortunately the PP bolts are on the other side of the rubber layer in the dual-mass flywheel from the flywheel bolts.  Half your effort will be winding up the rubber layer. 

 

I used a HF pry bar and a spare 10mm bolt to keep the flywheel from turning.  I'd previously ground the end of the pry bar to fit cleanly in the "tooth gap" of a Miata flywheel.  Turns out the Porsche tooth gap is the same size.  When torqueing the flywheel bolts, a few blocks under end of the pry bar keeps it in place.

 

 

You are supposed to torque the flywheel bolts to 19 ft. lbs, then "another 120 degrees"  Dempsey isn't very helpful here, suggesting you use a protractor.  But there's not enough room down there to get a clean 120 degree swing with your wrench.

 

I used my extra torque wrench.  Putting a large extension in it, I held the extension with one hand.  Starting with the wrench straight down, I spun it 180 degrees and counted the number of clicks it made:  18 clicks for 180 degrees.  So 12 clicks for 120 degrees.  For each flywheel bolt I started with the wrench straight down, swung it as far as possible, and counted the clicks.  Then I pulled it back to vertical.  I did this several times until I had done 12 clicks worth of tightening.

[Dennis Nicholls]

The LUK 20-016 clutch kit is a bargain at $300 shipped from RockAuto.

 

It includes a Sachs clutch disc and pressure plate.  And the part numbers matched the factory parts that I took off my car.

 

It also includes a TO bearing, pilot bearing, clutch install tool, and a packet of special "spline grease".

 

The clutch I took off my car appeared barely worn.  But I installed all the new parts.  After getting the car back together, I noticed - as many others have reported - that the amount of leg effort pushing down the clutch pedal was considerably reduced.

 

The PO was some air force guy who bought it from the local dealer.  A number of months later he was deployed overseas. leaving his wife to drive the car.  She could barely push the pedal down.  The dealer told her a new clutch would solve the problem and that they would gladly do the job for $1,400.  She ended up selling the car back to the dealer instead.

 

I'm guessing that the spring fingers in the pressure plate lose their tension after being clamped tightly for 14 years.  This would be why a new clutch needs less leg effort to disengage.

[Dennis Nicholls]

I've put 100 miles on the new components, and I don't hear any expensive noises.  I ran my Durametric after a drive and checked my cam position deviations.

 

Before:  cam pos 1 dev. - 4.42 degrees,  cam pos 2 dev - 4.25 degrees

 

After:  cam pos 1 dev - 4.42 degrees, cam pos 2 dev - 4.30 degrees

 

No chain slipping teeth there.

 

I also finished up the quick-and-dirty AOS test from last month.  The oil filler cap comes off easily, but I didn't have the Durametric hooked up to read idle RPM ranges.

 

Cap in place:  idle 685 - 705 RPM

 

Cap removed:  idle 700 - 720 RPM

 

Naturally those ranges are an eyeball from the displayed graph.  I'd elected not to change the AOS at this time, due in part to a comment by Jake Raby that he's "never seen" an AOS failure in a car in the Rockies.  I guess the lower atmospheric pressure at altitude helps.  The AOS design seems "marginal" and it doesn't take much for it to have improved reliability.

Edited July 1, 2014 by Dennis Nicholls

[Dennis Nicholls]

I'm an former engineer so I prefer to work to a detailed checklist.  I bought Dempsey's 101 Projects book but made up a binder for the checklist.  I cut-and-pasted his on-line instructions into a word document, and copied into each hyperlink the full referenced text.  Then when he not-helpfully says "assembly is the reverse of disassembly" I inserted a second copy and cut-and-pasted each step in reverse order.  When you get to the "Dempsey set screw method" I inserted "jump to LN instructions here".

 

I then copied the LN Engineering instructions (rev. 18 Jan. 2014) from the .pdf into another word document, changing the font and adding large spaces between the steps to make it easier to read and annotate.  My notes are offered here for other's future  use.

 

6.  Lock cam(s) for bank 1, cylinders 1. 2. 3.  Insert pick near center of the green plastic plugs because they contain a metal washer you can't pick through.  Cam locks need an M8mm by 1.25mm thread by 20mm long bolt to attach.

 

15.  The LN supplied center flange nut can be spun with a 12 point 11mm socket, or even a 7/16" box wrench.  The "spare" o-ring is called that because there's one already installed inside the LN hub flange (hidden).

 

19.  To install a sprio-loc, don't try starting the inside end and then spinning the spiro-loc into position.  This won't work.  Instead start the  inside end and hold it with your finger, going around the stationary spiro-loc with a small screwdriver pushing it into place a bit at a time.

 

20.  Sold in plumbing supply places is clear silicone grease as an o-ring lubricant.

 

21. The LN supplied bolts take a "female Torx" driver size E10. 

 

22.  Wicking (green) Loctite is Loctite 290.  Hard to find:  google led me to a model helicopter shop that sold it cheap.

 

23  I replaced the funny green rubber o-rings along with the metal sealing rings.  The old green rubber O-rings were as hard as plastic.

 

24.  Before installing new green cam plugs, remove crank and cam locks, spin crank twice 360*, re-insert crank and cam locks as timing check.  Then remove locks and install new cam plugs.

 

23.  It was suggested that I NOT install new case bolts without any specific reason, and I didn't.

 

28  Pull fuel pump fuse and turn over engine to built oil pressure prior to actually starting the engine.  Fuse location varies from year to year and you need to look in the Bentley manual section 97 for tables of fuse locations.

Edited July 2, 2014 by Dennis Nicholls

[boxster_nut]

Enjoyed reading the details, as I have a 97 with 30K miles and am wondering about doing the IMS + clutch job...Was just quoted $2200 USD for the whole job - as I had PS pressure hose replaced.

 

So, just curious....did you have your car on a lift or on 4 jack stands.......I HATE working on my back....lol

 

best regards,

John

[Dennis Nicholls]

This was a full "home mechanic" job with the car up on 4 "6 ton" jackstands.  See the photo in post #4 above. I bought the heavy-duty HF jackstands not so much for the weight rating but because their wider base seems more stable.

 

The $2,200 quote sounds cheap.  There's $1K+ of parts in there and I shopped for price (e.g. $300 LUK clutch kit from RockAuto).

[boxster_nut]

Thanks for the insight.  I guess the question that I should have asked but didnt: Is the IMS bearing prone to failure on a 97 boxster?

 

I read the law suit and settlement - model year 2002-2005, will cover up to 10 years, yada, yada, yada.  But for me, the question is is the 97 boxster susceptible?

 

Best regards,

 

John

[JFP in PA]

Thanks for the insight.  I guess the question that I should have asked but didnt: Is the IMS bearing prone to failure on a 97 boxster?

 

I read the law suit and settlement - model year 2002-2005, will cover up to 10 years, yada, yada, yada.  But for me, the question is is the 97 boxster susceptible?

 

Best regards,

 

John

 

Any of the M96/97 engines are at some level risk for IMS failure, including the last design with the unserviceable IMS bearing.  As yours is a five chain, dual row IMS; it is one of the better units, but still susceptible to failure.

[Dennis Nicholls]

Is your engine original?  The 1997 engine had  many more problems than just the IMS bearing:  porosity, slipping sleeves, D-chunk failure.  If it was replaced you have no idea what kind of IMS bearing yours contains.  Does your engine serial number have an "X" near the front? 

 

After this morning's drive I've put on 400 miles since my IMS work.  No funny noises so I feel I can declare a successful job.

Edited July 11, 2014 by Dennis Nicholls

[san rensho]

So what was the condition of the IMSB you took out? I assume it was a double row. Was it rough,loose?

[Dennis Nicholls]

Rensho,

 

I'm not sure how to answer your question....I peeled off the outer shield and it looks fine inside:  some grease left. As far as I can tell it probably would have held up for a very long time. 

 

Now at 567 miles after upgrade, running better than ever. 

Edited July 26, 2014 by Dennis Nicholls

[mikefocke]

May I suggest you send your comments re the LN instructions and your experiences to Jake and/or Charles and maybe they could influence the next rev of the instructions for the better.