Porschetech3

If you don't find a broken timing chain causing the cam timing to be off, you had better assume the IMS sprocket has slipped on the shaft...

This is a fault that has been seen quite a bit and will require you to have the IMS repaired. LN does a pinning procedure to the sprockets to ensue they do not slip on the shaft, they are just press fit on the shaft and can sometimes slip if they are stressed to much like say if something hard goes into the scavenge pump and it tries to seize..

If you don't find the root cause I would condemn the IMS for slipped sprocket..

I have seen people just assume it is an unsolved mystery and just repair what they can find only to put it all back together and have it jump time again and bend all the valves due to IMS sprocket slip...

jwittock

Checked the invoice for the IMS bearing replacement and is shows as a 399Euro "m96 IMS bearing single row" -> This was 6 years and 32 000 km ago.
Does look like I might need to install the LN Engineering kit. I'll post picture once engine is out before doing any work.

Further inspection of the invoices shows this in 2018:

• 4 camshaft plugs
• 2 alu o ring chain tensioner
• 1 camshaft lid
• 1 scavenge oil pump
• 1 camshaft sprocket
• 1 camshaft pulley central bolt
• 997 oil pressure valve
• bunch of o-rings for various parts

So someone has definitely been in there before.

Started removal of the engine, once it is out I will take extensive pictures and post here before doing anything. Seems like there is a lot of experience out here willing to help me do things right, which I appreciate a lot!
Bentley's Service Manuals has arrive (4 weeks early, yay) that will help a ton, initial impression is that this book is golden.

Thanks,
J

pdxmotorhead

I have that manual + the torque spec book that Flat6/Ln published. It's very handy had multiple things that didn't make it to the Bently.
I also had the book 100 Porsche projects, which has a ton of good photos for removal and reinstall of the engine + a few tips on making some tasks easier by a bit.
Oh and enough pics just for good reference when I ran in to something going back in I did not remember..

Both good books IMHO and were worth the $..

If you have to get deep enough to get the heads off,, stop and use a cylinder bore gage to check taper and oval ,
its fairly rare for a engine to be in spec after this amount of time.

jwittock

So when I drained the oil, bad news greeted me. Pictures are worth more than a 1000 words is a saying in my area:



metal flakes



metal flakes




So at this point in time, I do think the block needs to come apart. Pretty depressed at the moment as I only got to enjoy the car for 2 months. Tomorrow I will try to find some time to take pictures of the block and to separate the gearbox from the block so I can see the state of the IMS and RMS.
I think that at this time the quickest way for me to enjoy the car again is to find a new engine and than take my time to determine what to do with this block. Rebuild myself using Jack Raby's engine rebuild series as a guide, or send it out to have it rebuilt.

I'll keep you informed.

hardtailer

I'm sorry for you reading this and appreciate even more so that you've posted your findings.

Good luck from here on!

jwittock

One more observation: when turning crank manually intake cam does not move, exhaust cam does move.

will take a look at he bolts connecting sprocket to intake cam, I expect to see carnage.

jwittock

One more observation: the shavings appear to be non-ferro, a magnet is not attracting the shavings

amargari

Since you have a three-chain engine, the only thing it can be is a broken cam sprocket, cam bolt, or broken cam.

168Sierra

It is possible that the bolt that hold the vane cell adjuster assembly on the intake cam has come loose or broken. The vane cell assembly also includes the intake cam sprocket. The intake cam on a three chain engine does not have cam sprocket bolts (see photo in post 39), only the long bolt through the center of the vane cell adjuster assembly. If it wasn’t cleaned good ( perfectly dry, no oil) prior to being tightened , the bolt could have come loose

yelcab

OK, no more guessing. Open up the cam cover and you will know what broke.

jwittock

Progress report: Removed scavenge pump on bank 1, the one connected to exhaust cam shaft:



not ideal ...

As soon as I took it out, the key connecting pump to camshaft fell out, and was missing some bits.



no longer stock ...

You can also see part of the sprocket around the key has broken off.



very unhealthy oil scavenge pump.



pump after weightloss program


Next up:

• remove flywheel to take a look at the IMS and RMS, although I don't expect to see much there. (I have been proven to be utterly wrong many times before though)
• Check if I can remove what seems to be a plastic cap at the location of the intake camshaft, right above the oil pump. Since the intake one no longer rotates, I expect that the connection from sprocket to camshaft has been undone.

So the current story the evidence is telling me, and I do invite all of you to tell your version of what you see, is that something broke loose somewhere and got stuck in the scavenge pump. This caused connection between pump and exhaust cam to break, and most likely that shock also broke the connection between intake cam sprocket and intake cam.
Question: could this shock also have made the gear on the IMS shaft to move, as that is a press fit connection? -> only way to find out would be to completely disassemble the block? So that IMS shaft can be taken out and connection between IMS shaft and gear to be inspected?

I started making some videos with my gopro, I am considering posting them on youtube so I can share my journey on video. Let me know if there is interest in that.

Cheers,
J

yelcab

This is not the first time that a scavenge oil pump froze up due to foreign objects. I expect to see bent valves on that bank.

allcool

Agree with yelcab, when cam stops turning in sync with pistons, valves hit pistons and bend/break in an interference type engine like our 996.
Crank/rods can also be damaged.

I know this is not what you want to hear, but it needs to be said for all those that might do the same, as you're not the only one. As many most people do the same and drive till it dies... This is wrong from a mechanical/economical point of view for a 996.

If you stopped driving at first sign of trouble, probably would have $aved valves from hitting pistons and maybe the bent rods you probably have now along with possible crank damage, and more, etc. All very very costly parts for this extremely expensive 996 engine that probably might have been saved for a rebuild if you listened to your engine and stopped driving,,

This was your red flag to stop immediately and get towed v
"When the rpm got below 3000 I lost all power (engine did not die), and with full throttle it slowly picked up speed until it reached 2700 to 3000 rmp when all power returned and the car lept forward in a jerk."
"During the last 10km of running, check engine light came on, fuel light came on, abs errors, pcm error all came and went."

What I don't understand is, you seem like a mechanically inclined type, so why not get a tow, knowing the possibilities if you continue...?
And its not like you just drove on for a moment, you pushed on for 10km knowing something major wrong was going on inside your engine...
"Tried to make it home, but after 10km of this it finally stalled and did not want to start again."

IMO, these 996 engines are so costly to fix, at the first sign of engine trouble that you don't understand fully, STOP driving immediately or pay the price.

To be fair, at over 100k miles the engine would have needed a full rebuild as soon as this problem started, but if you stopped sooner than driving till it died, you would of had a less expensive rebuild with many more very expensive rebuildable core parts. now you have more costly options...

Just my advice for those in a similar positions, take it or leave it....

jmo

hardtailer

Yes, I'm interested in seeing those

996-CAB

100% what allcool says. Pull over and call a tow truck at the first sign of engine trouble that you don't fully understand. It sucks and ruins your day, but the alternative is often worse.