Chain noise, actuator rails, and more.. a bit of sleuthing

[bg305]

My Box had high cam deviation on bank 2, (2001, 3.2L, 53k miles) and then suddenly earlier this year I noticed what I believe is chain noise. (more on that in this thread: http://986forum.com/forums/boxster-general-discussions/80398-engine-noise-diagnose-assistance-possible-vario-cam-actuator-pad-chain-issue.html)

Here is a video of the noise.

I stopped driving it, removed the motor and tranny and started by opening up the bank 2 side as it had the large deviation. Interestingly, while one of the 2 pads (the top one) was worn significantly, it was not "broken" just worn. I also found it interesting just how unworn the other (lower, towards the head) pad was. Any one seen this type of variation before?




My (first) big question now is how safe is it to rotate the crank with the cam sprocket hanging like it is? I have new actuator rail guides ordered with pelican, but it will be a bit before they get to me. I would like to rotate around to get bank 1 at TDC so I can open up that side (I believed that is where I heard the noise). Is it better to wait for the guides so I can put bank 2 back together first, or can I just guide the loose chain with my hand? I have all the tappits out, bagged and labeled and no cams pushing down, so I would assume the values would all be clear of the pistons? I am making an assumption that the specific links on the long chain between the IMS and the exhaust cam sprocket do not matter as long as the crank is at TDC (and the correct one over the whole 720 degrees) and the cams are in time with each other and lined up correctly to TDC (intake slot facing directly towards block for bank 2) which i will deal with putting them back in.

Another thing I wanted to note was that the colored links of the cam chains were not set on the dots on the cams. There were however to to my understanding the correct number of links between the dots (15 and 6). I am guessing experienced techs may not care much about the colored links being right so long as the amount of links is correct but was curious to see if others encountered it, is it a clue that someone has been in there before, or perhaps the opposite as the original manufacturing process of the engine only needed to verify the amount of links, not color?

Another reason I want to turn the crank is to better see piston 4. I stuck a scope in the spark plug holes and noticed that the top of that piston looks really dirty.. however it is currently at TDC so I don't know if it is just because it is so close to the camera. I wish I had done a leak down test before opening it up.

Here is an image of piston 4:


And here is another (i think it was 5) for comparison:


Definitely getting to know this engine, hoping that I can find the root cause of the noise!

[Homeoboxter]

Dissimilar wear on the two pads is normal. Depending on the rpm and the related position of the actuator one of the pads gets more pressure than the other. I think depending on what rpm range you use the car the most determines which pad will wear more.

As long as you don`t remove the tensioners on the other bank and everything is timed and obviosly you don`t remove the IMS flange, it`s safe to rotate the crankshaft if you removed the camshafts. Just make sure you hold the chain tight so it won`t get jammed in the crankcase.

The colored links need to be set only at assembly. If you want to check timing you need to look at the positions of the camshaft marks relative to TDC.

[bg305]

Originally Posted by Homeoboxter

Dissimilar wear on the two pads is normal. Depending on the rpm and the related position of the actuator one of the pads gets more pressure than the other. I think depending on what rpm range you use the car the most determines which pad will wear more.

As long as you don`t remove the tensioners on the other bank and everything is timed and obviosly you don`t remove the IMS flange, it`s safe to rotate the crankshaft if you removed the camshafts. Just make sure you hold the chain tight so it won`t get jammed in the crankcase.

The colored links need to be set only at assembly. If you want to check timing you need to look at the positions of the camshaft marks relative to TDC.

Okay thank you for the guidance.. I turned the crank about 180, checked cyl 4 again with the bore scope and I think that was a false alarm.. looks a bit different when the camera is not right on the top of the piston.

Still dirty, but I really am not sure I would know if it is good / bad / indifferent.. My plan was not to remove the heads unless I found something that required it, guess I will stick with the plan so far.

I then continued around another 180 and relocked TDC for bank 1. I did not get as far as pulling the cover and cams on bank 1, I realized I was going to have to get it off the cart I had it on to get to the chain tensioner at the bottom so I got it mounted on my engine stand. Hopefully I will find some time to get into bank 1 this weekend, dying to know if I am going to find anything.

The more I research the more I see discussion on various ticking type noises being related to failed chain tensioners. I was planning on replacing all three as part of this especially since I heard a couple of chain slap startups over the prior year (separate from the noise in the video which just appeared and is constant). Anyone think my noise might be tensioner related?