logray

It's been a month long journey into the depths of my 1999 996 C2 M96-01, but I am finally there and the car is on the road again!

If you want to skip all of the boring commentary and head straight for the annotated pictures, then here is the link:

https://picasaweb.google.com/1085493...12361/Engine02

(the email address associated with this account is not monitored, PM me or post here if you would like to send me a message)

Some commentary about the process for the readers.

PROBLEMS

1.) In the past 5,000 miles, oil consumption had gone from about 1 quart per 1500-2000 miles to 1 quart per 1000 miles. Still within Porsche spec, but such a rapid increase was worrying. I also knew that there were a ton of leaks that needed to be addressed, such as the spark tubes, camshaft covers, cam solenoid cover, AOS tubes, oil filler neck, and on and on and on. However leaks aside, the big indicator here that something was afoot was that bank 1's tailpipe was accumulating soot and producing purplish smoke on startup and high RPMs much more so than bank 2's pipe which was not exhibiting these issues.

2.) The oil pressure was fine at start-up, 5 bars. However when the car was warm it would fluctuate very slightly a few points in either direction of 1 bar at idle. Sometimes .8 bars. Cleaning the sender terminals did not help. I did not drive the car very long with this condition. In fact, barely at all before I decided to do this work. You don't want to mess with low oil pressure. This problem and the next one were what really got the ball rolling on this endeavor.

3.) There was an increasingly worsening knocking from bank 1 (1-3). The knocking would "seem" to stop after about 30 seconds on cold start, and I thought that this could be lifters or tensioners taking their sweet time to fill up with oil. One time the ticking lasted for 5 minutes. That really put the icing on the cake for the decision. After much Internet research, I determined that it could be stuck or collapsed lifter noise, because I couldn't tell whether it was coming from the top or bottom and that it would seem to go away after the car had oil filling the parts (but it was actually still there). In the back of my mind I also had thought that it could be oil pressure, blockage, valve guide, still could be worn rings, or perhaps issue with a chain tensioner or variocam unit as well. (after researching more and using the screwdriver stethoscope trick, I discovered that the knocking was present in cylinder #2, in the bottom end, but it was also present in #1). The exhaust valves in cylinder #2 were most heavily coated in carbon as well. Eventually, this realization and discovery later that the lifters were OK from my non-professional mechanical knowledge prompted me to pull the heads and have a valve job performed by professionals.

ACTION

Each problem individually above one might address on the surface by changing or swapping spark plugs, coil packs, and oil viscosity (which I had all done), however when those didn't have a noticeable affect on the issues, I decided to do something about the nervousness and drop the engine.

A bevvy of parts were ordered. Because a lot of the parts on this car is relatively inexpensive, I decided to R&R many of the components which I had isolated before removing the engine. For example the 4th and 5th chains cost only half that of the bicycle chains I go through several times a year on my road bike. Each of the three chain tensioners were less than $100. Some people might question why I replaced both oil scavenge pumps after only 75,000 miles and 12 years of life, however in the overall cost of the project the investment was minor. I'm glad I did too, because one was not rotating as freely as the other, and no where near as freely as a new unit. An LN engineering billet hex oil pump driver and genuine oil pump spring and piston were also sourced.

Waiting for the parts was actually the most discouraging part of the entire process for me. A few times I had to wait for parts from Germany which meant 7+ days. I replaced nearly every gasket, o-ring, and washer I could which was external to the engine, including some which are internal such as the valve seals (done by the machine shop) and head gaskets (can't avoid doing that or the bolts if you remove the heads). In hindsight I should have ordered the ARP studs for just a few hundred dollars more than the stock single use head bolts. I ordered 24 new "BMW" INA lifters, in case they were some of the source of the problem. Also in hindsight, instead of ordering individual gaskets and orings I could have ordered the complete gasket set, which probably had more in it than I was going to use but would have been easier (although somewhat more expensive) than ordering ala carte.

WORK

Here are the major highlights on what I replaced or work performed.

Complete valve job was performed by Riebes machine shop including: Cleaning, gentle bead blast, and light resurfacing, vaccum and pressure test. Three way valve cut, 5 new valve guides (2 were horrifically worn - the source of the knock), new valve seals, and overall inspection for valve train components (springs, etc.).

The machine shop also resurfaced my fabspeed stainless bank 1 exhaust header, it was badly bowed out in the center which plagued me with constant re-torquing, stripped threads, damaged bolts, and a lot of helicoils later. GOOD BYE exhaust leaks!!!!

Head gaskets
Head bolts
Variocam ramps (two were heavily pitted and scored)
4th and 5th timing chains
24 new (old style) lifters
LN engineering billet oil pump hex driver
OEM oil pump pressure spring & piston
Both oil scavenge pumps
Oil pressure sender (cleaning the terminals did not help)
All three external chain tensioners (all were scored)
Replaced many coolant and AOS hoses
New air oil separator
Countless gaskets, o-rings, & washers
Micro encapsulated rear case bolts
Replaced water pump (oem, peace of mind)
Replaced thermostat (oem, old one was lazy)
Resealed and inspected oil pan
4 new lambda sensors (3 were very "slow") - killer deal from Amazon
6 new spark plugs (packs have about 20k on them)
Fuel injectors sent out for test, cleaning, orings, and new filters
Oil filler tube and cap
New "04" coolant cap
10 quarts Castrol 5w40
Oil filter
Cleaned IACV
Thorough cleaning of engine exterior
Cleaning of any interior or exterior part I reinstalled
Thorough Intake plenum cleaning
Inspected DMF and clutch
Replaced about 1 quart of CHF P/S fluid
Inspected polyrib belt
New SAI check valve, hoses, tubing and elbows, and cleaning
Repainted coolant tubes
Flushed 12 year old Porsche coolant out and replaced all coolant with Peak Global using Uview Airlift 550000000000
Cam caps
Ordered new RMS but didn't install because old was bone dry

!!!!!!RESULTS!!!!!

The results of all of the above are restored confidence in driving the car. The oil leaks appear to have vanished, since the engine is so clean it is easy to spot fresh oil. Low end torque seems to have dramatically improved on the few drives I've taken. Although I've taken it there a couple times, I haven't yet "fully tested" the high end RPM range because I'm going to give it a bit of a break in and "get comfortable with the rebuild" period first. Oil pressure now stays dead straight on at 1.2 bars hot idle and 5 bars cold idle. Last and certainly not least, NO MORE smoke at startup or high RPMs (thank you valve job). Time will tell if the soot or oil consumption returns. NO MORE ticking or knocking (outside of normal lifter and valve train noise I hear on any car). Thanks to the new thermostat the car gets to temperature much more punctually than it used to. The engine idles much more smoothly than before, it stays pretty dead level on 680 rpm - whereas before I'm sure there were some leaks in the system it would fluctuate some, the plugs were fouled too so not surprised. Warm idle numbers are pretty much dead on with the factory DME set points.

Load signal 1.6 ms
Air mass 20 kg/h
Mat film MAF 1.35
Ignition timing 4.5 to 7.5
Spec air mass 17 gh/hr
Spec air adapt 1 kg/hr
Injection time 3 ms
Oil temperature 207.5F (stage 1 is on, idling on a hot day in my garage)
Oxygen sensing 1-3 1.04 avg
Oxygen sensing 4-6 1.03 avg
Range2 Cyl 1-3 FRA .98
Range2 Cyl 4-6 FRA2 .98
Range1 Cyl 1-3 TRA -0.14
Range1 Cyl 4-6 TRA2 -0.14
02 ahead cat bank 1 fluctuating .09 to .77
02 ahead cat bank 2 fluctuating .09 to .77
02 behind cat bank 1 fluctuating .09 to .71
02 behind cat bank 2 fluctuating .09 to .71
Cam 1 deviation 3 degrees
Cam 2 deviation 3 degrees (was 0 before I did the work)
Rough Running Thresh 10.5 to 10.1
Rough running occasional spikes to 1.5
Segment A 1
Segment B 1
Sense wheel adapt .0007
Misfire detection 0

ISSUES

Not to say that my work was perfect, because I had one weeping perimeter head bolt that wasn't torqued properly, I damaged one of the coolant hoses upon reinstall (new one ordered), broke the stupid plastic AOS coolant coupler near the oil fill tube, and the oil filter housing was not torqued to spec (next time I have some spare cash I'll probably do the spin on adapter, I'm so sick of that stupid plastic housing). Bank 1 was ticking badly upon first start, I thought for the worst that I had to drop it again, but thankfully it was just a loose/bad spark connection. I also improperly routed the throttle cable and as a result the DME was confused about the throttle plate angle at first startup, and the idle was stuck at 1200 RPM. Both variocam actuators actuated properly when activated with the PST2, and power through the range is consistent and smooth.

The only nagging things I am left with which I am somewhat kicking myself is noticing after the fact that the crank pulley appears to have more run out than I would like to see. I will be measuring this run out soon and investigating the possibility of a flat 6 harmonic under-drive pulley or perhaps a new engine. That and I don't think I have the timing 100% spot on, but it is close.

I am also nervous about a potentially poor decision to abstain from loctite usage on the variocam actuator, lifter carrier, and bearing saddles. When I removed those bolts they appeared to be "factory fresh" oily and brand new for lack of a better term. So I decided to just re-torque them to the specific tightening sequence and value. It wouldn't be the end of the world if someone told me I did that wrong and should really consider removing the cam covers again. At least this time I would be able to do the work faster and with much more confidence.

DISCLAIMERS

I AM NOT A MECHANIC. I am a computer professional, and have done most of the work on the cars or boats I've owned or used for the past 20 years. Some of the things I comment on in the photo gallery might be done "incorrectly" or be appalling to some who are in this trade. But, I have to say it got the job done and I'm not afraid to drive my car anymore.

THANKS

First and foremost rennlist and renntech are perhaps the best sources of useful information you can find, since there is not a ton of info about these engines elsewhere, unless you have the money to pay for one of Jake's seminars (which would be totally awesome) or are a Porsche employee. There are several great "DIY" engine drop websites as well, http://www.nutrod.com, http://986fix.com, and http://www.oz951.com/public/enginedrop.htm. http://101projects.com and Wayne's Boxster book is great as well for M96-01 info, especially for summarizing the cam removal DIY - however seemed somewhat "incomplete" to me since it is light on documentation for a few critical things out such as ensuring proper timing procedure and torque settings are carried out. In the end, nothing can replace the authentic work shop manual. I wouldn't even try to attempt any of this without access to that and a Durametric and/or PST2.

Thanks to all the suppliers, Bob @ http://www.sunsetimports.com, Henry @ http://www.porscheoemparts.com, http://www.pelicanparts.com, http://www.rmeuropean.com, http://www.4wheelsautoparts.com, and http://autoatlanta.com.

And certainly THANK YOU PhillipJ, Dharn55, Loren, Don and crew at Riebes machine shop, Dr. Injector, and anyone else who provided any help including those that helped fund this project through the sale of some of my parts!

Now it's time to take a drive!

GTA_G20

wow, good job. Was this your first engine rebuild?

Phi1720

Awesome work man. Thank you for the DIY contribution to the site!

Enjoy the 996's new lease on life, and I wish you hundreds of thousands of carefree miles.

ogun228

I am in awe. Though I don't understand most of what you detailed in your photo history ( I don't wrench),
I followed the sequence to the end. You should be proud of the attention to details and thoroughness. Congrats!

fasteddie99

Very impressive. She's good to go for a while now. Enjoy, you earned it!

dennis hiip

Great contribution to the forum!! One question. Doesn't this seem like excessive wear at 75K miles or did I get that wrong?

Flat6 Innovations

Great job.. I would certainly use a proper cam timing tool, the tool forces the cams into position and holds them perfectly and tightly during the tightening procedure of the drive sprockets. Without doing this, you will never get it spot on without using the split overlap method and treating the engine like an aircooled 911.. The problem is the cam timing numbers that allow this to be done are not published anywhere. This was one of my first challenges, back before cam timing tools were even available.

You accomplished a DIY task that few have attempted and fewer have successfully completed. It sounds like you did your homework and took your time.

The pictures depict a 75K mile M96 engine well, thats almost exactly what we see time and time again, yours is absolutely text book.

We had most of those special order parts from Germany in stock.. I really do need to get my web store up to date. We have to stock a lot of this stuff for our procedures and engines.. Getting parts can be a bitch, its one of the achilles heels of working with this engine. It is much better than it was prior to 2008 when literally everything had to come from Germany... Thats why we started building so many of our own parts.. It really sucks.

A couple of questions:
-How did your cylinders measure up for ovality and taper? Especially the #2 and #5 cylinders?
- It doesn't appear that you split the crankcase from the parts list, is this correct? ( I didn't see piston rings, bearings or carrier bolts and thrust shims on the list)

Glad its performing well.. These engines are only difficult to work with because everything is sequential and procedural. Learning the correct sequence of assembly is the key to making the job simple.

Have fun!

RPMulli

Nice work. I look forward for the day (later than sooner) that I can tear into one of these motors. My MK1 with 100k is still running strong though with no leaks or issues(knock on wood). I may have to replace my chain tensioners soon since I get some minor chain noise somedays on start-up.

RPMulli

BTW: GREAT pics!! Thanks for the post!

pterfloth

Excellent write up and great job! Thank you very much for the extensive pictures and documentation. Very much appreciated.

CT944

Great pix, congrats!

chsu74

I have been following your rebuild and questions with commanding respect. My favorite picture from the threads is this one with war wounds.. Way to go!

https://rennlist.com/forums/8704303-post3.html

fpena944

When all was said and done was the cost anywhere close to purchasing a remanufactured engine and installing it yourself? This is something I've considered doing in the future as my car is up to 107k miles right now. No problems but just preparing for them if they do happen.

rons2112

What a great write up! I really enjoyed pouring through all the photos and details.

John@Fabspeed

Very nice and well done. This is going to turn out very nicely. Keep us updated with pictures and info.
thanks,