camshaft question
04-06-2016, 06:25 AM
#31
Rennlist Member
There are two failure modes as Kevin has stated. The actual intake cam sleeve that's press fit inside the cam can spin as much as it wants. Worst case scenario is that it cuts off the oil supply to the VVT intake cam actuator. It can actually spin enough that the holes once again line up. There have been reports of people getting the codes, and continuing to drive until they go away and the car feels normal again. Of course the sleeve can continue to spin and intermittently block the oil feed holes. Not recommended to do this. Again, this sleeve is inside the hollow camshaft.
The second failure is the actual cam gear sprocket/VVT mechanism CAN spin relative to the camshaft itself. The reason is the cam gear is not degreed or keyed on the end of the camshaft. It is simply held in place with a tiny "friction disc" between the cam gear and the camshaft snout itself along with the compressive pressure of the cam gear bolt. As in my case, I had failure #1 first. The cams were pinned and replaced. Immediately, failure #2 occurred twice. We had to replace the cam gear itself, the bolt, friction disc, etc to correct the second issue. The failure #2 is much more dangerous because it does control the angle of the cam relative to the pistons and you can have top end damage if it slips enough. Mine only slipped enough to lead to bad misfiring at low rpm and idle (about 45 deg, best we could tell both times.)
The second failure is the actual cam gear sprocket/VVT mechanism CAN spin relative to the camshaft itself. The reason is the cam gear is not degreed or keyed on the end of the camshaft. It is simply held in place with a tiny "friction disc" between the cam gear and the camshaft snout itself along with the compressive pressure of the cam gear bolt. As in my case, I had failure #1 first. The cams were pinned and replaced. Immediately, failure #2 occurred twice. We had to replace the cam gear itself, the bolt, friction disc, etc to correct the second issue. The failure #2 is much more dangerous because it does control the angle of the cam relative to the pistons and you can have top end damage if it slips enough. Mine only slipped enough to lead to bad misfiring at low rpm and idle (about 45 deg, best we could tell both times.)
04-06-2016, 10:29 AM
#32
Instructor
Thread Starter
There are two failure modes as Kevin has stated. The actual intake cam sleeve that's press fit inside the cam can spin as much as it wants. Worst case scenario is that it cuts off the oil supply to the VVT intake cam actuator. It can actually spin enough that the holes once again line up. There have been reports of people getting the codes, and continuing to drive until they go away and the car feels normal again. Of course the sleeve can continue to spin and intermittently block the oil feed holes. Not recommended to do this. Again, this sleeve is inside the hollow camshaft.
The second failure is the actual cam gear sprocket/VVT mechanism CAN spin relative to the camshaft itself. The reason is the cam gear is not degreed or keyed on the end of the camshaft. It is simply held in place with a tiny "friction disc" between the cam gear and the camshaft snout itself along with the compressive pressure of the cam gear bolt. As in my case, I had failure #1 first. The cams were pinned and replaced. Immediately, failure #2 occurred twice. We had to replace the cam gear itself, the bolt, friction disc, etc to correct the second issue. The failure #2 is much more dangerous because it does control the angle of the cam relative to the pistons and you can have top end damage if it slips enough. Mine only slipped enough to lead to bad misfiring at low rpm and idle (about 45 deg, best we could tell both times.)
The second failure is the actual cam gear sprocket/VVT mechanism CAN spin relative to the camshaft itself. The reason is the cam gear is not degreed or keyed on the end of the camshaft. It is simply held in place with a tiny "friction disc" between the cam gear and the camshaft snout itself along with the compressive pressure of the cam gear bolt. As in my case, I had failure #1 first. The cams were pinned and replaced. Immediately, failure #2 occurred twice. We had to replace the cam gear itself, the bolt, friction disc, etc to correct the second issue. The failure #2 is much more dangerous because it does control the angle of the cam relative to the pistons and you can have top end damage if it slips enough. Mine only slipped enough to lead to bad misfiring at low rpm and idle (about 45 deg, best we could tell both times.)
Holy S*%#!!!!!!! I know it's not common but man I'm gonna be a little paranoid now! But in reality nothing I can do so life goes on I guess.
04-06-2016, 10:40 AM
#33
Drifting
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this is why i need to find an aftermarket warranty just to cover the camshaft issue. I had a scare last year, don't want it to be the real thing.
Btw anyone have a DIY for Drain your gearbox fluid, front diff, and fuel filter?
Btw anyone have a DIY for Drain your gearbox fluid, front diff, and fuel filter?
04-06-2016, 12:02 PM
#34
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A418t81, I think your failure after the pinning happened because your tech reused the stretch bolt and friction disk. They are suppose to be tossed in the bin on tear down.
Cam slippage with this platform is rare.
Cam slippage with this platform is rare.
04-06-2016, 12:34 PM
#35
Rennlist Member
I know when the dealer replaced my cam, the tech was very clear about not re-using those parts (bolt & disc) and had ordered new ones for reassembly..
04-06-2016, 12:56 PM
#36
Rennlist Member
Those parts were replaced both times. He was a master mechanic at a large Porsche dealership for a while and said he's seen this happen one other time.
04-06-2016, 12:58 PM
#37
Race Director
i've done all of that. i can write you a diy if you like.
04-06-2016, 01:19 PM
#38
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He had a bad day then.. He got oil on the surfaces, it happens.. Porsche has used this system since the 993. You have to really be careful with oil getting on the mating surface. Every engine would be at risk leaving the factory if this method and components (shims and bolts)didn't work correctly. I have never had one loosen up.. I use acetone to prep the parts.
04-06-2016, 01:56 PM
#40
Rennlist Member
He had a bad day then.. He got oil on the surfaces, it happens.. Porsche has used this system since the 993. You have to really be careful with oil getting on the mating surface. Every engine would be at risk leaving the factory if this method and components (shims and bolts)didn't work correctly. I have never had one loosen up.. I use acetone to prep the parts.
Cool cafe. 
04-06-2016, 05:20 PM
#42
Rennlist Member
Fidelity paid to fix both sides, but I took on the risk the other side not needing it. Since I planned to pin both intake cams regardless, I didn't hesitate. I think the cam's themselves are $1700.00 each if you replace them.
04-06-2016, 06:49 PM
#43
Rennlist Member
The total was actually around 6k to begin with but by the time he pulled the motor two more times, and I had to replace the cam gear itself at 600 bucks, it ended up around 8k. Both cams were fixed but only the passenger side bank 2 which was the side that spun needed the new cam gear.
