Jim-c

2003 996 C4S 60,000 miles

It was time for a new clutch. I installed a LN IMS bearing and rear main seal while I was there. Both original bearing and seal looked perfect.

I locked the intermediate shaft with the 3 allen stud bolts. No way it moved !

It didn't even shift side to side, new bearing and cover went straight on.

I looked at the cams at TDC and marked them when I installed the 3 set screws /allen bolts.

After installing the tensioners I rotated the engine 360. One of the cams is off.
The lower cam on drivers side. Viewable from rear of the car. I assume its the 1-3 exhaust but haven't taken the time to look that up.

At tdc all cams notches are straight up and down except for one. Its rotated about 10 degrees. 1/8" from straight. I will try to get a picture.

I can't believe it jumped a tooth.

Ideas please ????????

fpb111

I think you need 720 to get #1 at TDC again. (4 stroke engine) Rotate it 360 again and see where they are.

Flat6 Innovations

Absolutely the cams can move when using that locking approach. Why? Because nothing is mechanically locking the cams, only the IMS assembly.

On any 3 chain engine chain wrap makes all the difference. This happens on exhaust cams more than intakes.

Jim-c

Thanks for the replies. I went another 360 and it's still off.
I would have gladly locked the cams, had I known there was a chance of something moving.
The instruction guide I was using only mentions the allen studs.

What's the best way to proceed ? Cam timing procedure per manual or can I just pull oil pump and rotate the exhaust cam?

Flat6 Innovations

Typically when something like this happens you already had a problem, it just wasn't noted yet. Typically this issue is related to a stretch chain, or an IMS drive that has slipped on the shaft.

This is why we urge professionals to do this job, so cam timing deviations can be checked while the engine is being qualified for the retrofit procedure. Its imperative to know if you have issues BEFORE you pull things apart.

Can you get pics of how far out that exhaust cam is with the crank locked at TDC? I need to see if its advanced or retarded, because that makes a difference in how you'll bail yourself out of this predicament.

This is why I have three IMS Chapters in my book, two of which are dedicated just to IMSR and specifically for 3 and 5 chain cam timing.

Jim-c

Thanks Jake

Here's a picture, while locked at TDC .
I did check location of cams before removing tensioners. They were all straight up and down.

Flat6 Innovations

Wow! To move that much that cam had to be "on lobe" and that's what happens when chain wrap enters the equation. Can you get a pic of the ends of both cams in the same shot?

Jim-c

I'll try for a photo tomorrow. The top cam is straight up and down / parallel with split line in case.

I'm not sure if it's possible but the more I rotate the engine the worse off center it gets. It was only an 1/8 off before I rotated 720.

Flat6 Innovations

I need to see something else from that photo :-)

KrazyK

Jim, not sure how you missed all the previous posts about locking the cams and NOT using the set screw method. Many of us have done the IMSB as a DIY job.

Now the good news is that since your a DIY guy, dropping the engine and trans is really not hard at all and some of us have some DIY's, tips, and shortcuts learned the hard way.

fpb111

"This is why I have three IMS Chapters in my book, two of which are dedicated just to IMSR and specifically for 3 and 5 chain cam timing."

Available for purchase? Where?

Jim-c

I can't believe I missed it either. I really did spend a week googling everything I could find for trans removal and IMS replacement. I guess I should contact the author of the instructions I used and let him know, not so good.

I'm currently researching how to fix my problem. Not having much luck.
I gather, so far, that I can remove oil scavenge pump on bank 1-3 and loosen 4 bolts on exhaust cam sprocket. I looked at the pump on car and there's not much room. I'm trying to figure out if the pump can be removed while engine is in the car. I read remove with tensions installed and don't remove with tensors installed.

I like to work on my own cars. I really don't trust "other" mechanics. Like you say, live and learn. At least I didn't cause irreversible damage ....... yet.

KrazyK

Jim, no need to panic or get in a hurry. I would not attempt this with the engine in the car. It is so much easier to work on when dropped. Most dont believe how easy it is until they drop it themselves. You can also do the chain guides and chains if needed.

Four full size jack stands, ATV/motorcycle jack, trans jack, two regular hyd jacks, few wood blocks, and you got it. Airlift to vacuum refill coolant is helpful. It was the most fun DIY I have done on my car and really gave me a chance to replace many parts and thoroughly go over the engine. 47" from floor to top of rear fender well gave me more than enough room. My engine is now completely leak free and runs fantastic.

Please keep us posted.

Imo000

You might get away with just lowering the engine a bit. I haven't yet done this but will in the spring when I'm replacing the vario cam actuator.

KrazyK

What happened or just for PM? Isnt that the $$$$ part?