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YOUR RESEARCHmost concern part regarding my M96 engine now
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Replace pads
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Read evidence and context
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Suggestion
You can't change the pads on the cam advance mechanisms with the cams in place.
Leading evidence: 'Replace pads' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check cam timing deviation' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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I don't think you will see many engines with 50,000+ miles that don't have significant wear on these pads.Too bad they were not designed to be replaced without taking the cams off.
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Suggestion
Check cam timing deviation with a Durametric to see if cam timing is steady or changes to judge excessive variation in cam timing.
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Suggestion · Original poster
(For other concerning parts, such as IMS, we can replace the IMS with LN kit if we worry about it, Also, we can replace the WP if we worry the broken blade of the water pump to cause the overheat and hurt the engine)
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Suggestion · Original poster
(For other concerning parts, such as IMS, we can replace the IMS with LN kit if we worry about it, Also, we can replace the WP if we worry the broken blade of the water pump to cause the overheat and hurt the engine)
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I don't think you will see many engines with 50,000+ miles that don't have significant wear on these pads.Too bad they were not designed to be replaced without taking the cams off.
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hi guys, for the M96 engine that just pass the 100,000 miles mark, the most concern parts to my understanding now are the guides for the cam shaft chain. because it is hard to know the condition of those pads without opening the engine. (For other concerning parts, such as IMS, we can replace the IMS with LN kit if we worry about it, Also, we can replace the WP if we worry the broken blade of the water pump to cause the overheat and hurt the engine)
The following pic is from another thread regarding his great DIY project. what is your opinion regarding these parts? do we need to change them ? what will happen if this part fail?
The smaller wear pads are under the cam chains to activate the Vario-cam. If the chain slides off this pad due to excessive wear the cam timing will be altered & result in engine damage. Check cam timing deviation with a Durametric to see if cam timing is steady or changes to judge excessive variation in cam timing.
those are pretty bad. I changed out mine because it was just starting to show wear when my engine was apart at 94k miles. Replaced pretty much everything I could.
My 944 S2 had something like that too on the cam chain. When I opened the head to remove it the little plastic piece crumbled in my hands.
I believe I dodged a bullet that day...
Now that I'm at 104k I probably should start to look at doing the same thing on my 996.
You can't change the pads on the cam advance mechanisms with the cams in place. You have to pull the cams to do this. And to pull the cams you really need to drop the engine (it is possible to get the cams off with the engine in the car but very difficult.). One the cams are off you may also be able to change out the pads in the IMS to cam chains, Can't quite remember if it is possible or if you have to pull the heads to do it. You can't get at the pad on the IMS to crank chain without splitting the cases.
When I had my engine out at 50,000 miles I replaced the pads on the cam advance mechanisms, they were badly worn. The IMS to Cam pads looked almost new.
There is no way to remove the cam pads if the cams are in the head.
Only way to do this is the way it's done in thread you posted.
edit. Dharn was faster
I just split a 40k engine in an MK2 car, all 3 tensioners look new (as does everything else, let me know if you need anything). I've also had a 110k mile engine from a 99 apart at 105k miles, the crank to head chain tensioners looked great, the cam chain tensioners had a little wear but not enough to warrant replacement.
See, posts like yours makes me wonder what the root cause of that wear is? Driving style? Warmup/cooldown procedures? Luck of the draw? Build quality? Manufacturing tolerances....
anyway, frustrating
sean
I would just stick to something like 0-40 unless you use your car mostly on track or exclusively for long trips in warmer climates. I'd imagine most wear would happen at start up...
Dang! I just bought 9l of Mobil 1 5W50 for next month oil change. The store didn't have any 0W40.
Porsche's approved oil list has 5W50 in it though .....
If you look atht he basic design of the 3.4/VarioCam/5 chain engine it is easy to understand why the cam advance pads were much more than the pads on the IMS to crank and IMS to Cam pads.
The chains from the IMS to both the Crank and the Exhaust cams are dual row chains, so the chains are twice as wide. The pads on these chain tensioners are 6"-8"+ long, and wide enough to fits the dual row chains they tension. And the amount of pressure that is put on these chains/pads is enough to keep the chains in place, but not nearly as much as on the cam advance chains.
The chains for the cam advance mechanisms are single row chains and the pads (2 on each side) are much smaller, Only about 3" long and about 3/4" wide. The chains serve two purposes 1. To drive the intake cam off of the exhaust cam. 2. To advance the intake cam relative to the exhaust cam. And it is the second function that leads to the high wear. The number of links between the cams is set. The relative position of the intake cam to the exhaust cam is changed by varying length of the chain travel between the cams.
Attached is a diagram of how this works. The cam advance mechanism puts pressure on the chain through the pads, on one side to advance the cam, and on the other side to retard the chain. This takes a lot more pressure on on a much smaller pad/pad area. Thus the higher wear characteristics of these pads.
The bottom line is that the cam advance pads are (or should be) a maintenance item. I don't think you will see many engines with 50,000+ miles that don't have significant wear on these pads.Too bad they were not designed to be replaced without taking the cams off.
Porsche did away with this problem in the 3.6/VarioCamPlus/3 chain engines. The advance of the intake cam relative to the exhaust cam on these engines is done through a vane assembly/mechanism on the end of the intake cam, so no more high pressure on pads on single row chains. These engine also have a system to vary the lift of the intake cams.
Hope this helps.
