ranger22

Since my car is no longer under warranty, I'm looking to do some preventative maintenance and upgrade to the latest specs for the cam adjusters. As I understand, Porsche has over time been increasing the hardness of the bolts that like to back out on the motors with single mass flywheel. My questions for the pros are:
1. Those that had their motors replaced under warranty, has the issue shown up again? Specifically, I am assuming the new motors have the latest cam adjuster assemblies, did this fix the issue for sure?

2. Are there any known aftermarket fixes out there? Has anyone else done preventative maintenance for this issue?

Thank you in advance for your assistance.

rnh204

Mine backed out right as I was out of warranty. Approx 32k miles. Porsche wouldn't warranty it but they did offer to replace the motor for only $65k assuming my core was okay. I said thanks but no thanks and had the motor rebuilt. It's been about 11k miles and no issues.

Dundon has a harmonic balancer to help correct the issue.

ranger22

Sorry to hear about your experience. I'm hoping to avoid that problem by getting ahead of it.

My understanding is that the harmonic balancer adds weight that essentially negates the benefit of having a single mass flywheel. I'm trying to avoid that.

rnh204

Another alternative is to get an aftermarket warranty. I have had Mercury Insurance after the incident and they have been great. Covers engine, transmission, electronics. Excludes clutch, cats and exhaust and suspension though.

GEICO might offer post factory warranty if you're the original owner of the car too.

DK7

@rnh

​​​​​​​how much was the rebuild?

Spyerx

Order new adjusters, send them to BBI Autosport. They have a fix they use on their big builds that have yet to fail. Or just call and talk to Betim about your options.

FLT6SPD

You can have safety wire installed on the intake variocam bolts. I have know idea what the improvements where made on replacement engines. Mine seized at 8500, at 10,300 now.

Here is a pic of the intake variocam that is the problem.

Last pic is safety wire used on aircraft.

CRex

^ I think recognize my own photos (top one with screws backed out)

FLT6SPD

Both were pulled from google images

Suren27

I was under the impression that they fixed this in .2s?

Are there any warning signs or sounds that preempt this or does it just go boom?

Don't want to jinx anything but have had 4.0RS Clutch, PP, LWFW since 5600mi, currently at 33k or so now.

Tom@TPC Racing

There are different approaches to help prevent the camshaft actuators bolts from backing out. Here at TPC Racing, our approach is to replace the M6 bolts with M7 bolts. And here is why-

The way we see it is that the OEM M6 bolts fit very loosely into the holes of the actuator body.



Its like driving a car on wheels that aren't hub-centric, instead its lug-centric and in this case centered only by the clamping pressure of M6 bolts.



The camshaft actuator assembly is comprised of three parts:
1) The sprocket/base, where the bolts thread into.
2) The main body, where actuation occurs, and where majority of the mass is.
3) The lid.
On this particular one, the main body was subjected to movement and the holes are elongated. We believe the ECU has been electronically compensating for the tweaked over time.



One tweak or one slip of the main body mass spinning at 7000+rpm it'll be off center and off balanced and the bolts will start backing out. Granted there are other sources of harmonic vibration that'll cause the bolts to back too.



The TPC Racing approach is to fit the actuator in a precisely machined fixture and then machine the sprocket/base, the main body, and the lid for M7 bolts that are much more precisely fitted to center the assembly and making it more stable. The M7 bolts naturally allow for greater tightening torque than M6 which results in higher clamping force for holding the three parts together better and with more resistance to slipping and bolts backing out. The 1mm difference in bolt diameter is a functional delta of 1mm multiply by Pi(3.14) making the M7 a much sturdier bolt than M6. And the nominal tightening torque that can be applied to a M7 bolt is 60-70% higher than to a M6 bolt.

ranger22

Good call Tom, this looks like the favored repair. I wonder if the replacements are going this route from the factory. I was told Porsche just released another tech bulletin on the cam actuators for the cayennes. Sounds like the incremental fixes they've tried haven't panned out. Your explanation makes the most sense to me.

Is there a reason nobody tries to locktite them as well?

Tom@TPC Racing

We have not had the opportunity to take apart and examine the actuator with the latest factory updated part number. It could be that they added Loctite or thicker bolts like we did and assigned a different part number.

In the past we have used Red Loctite on the OEM M6 bolts. Now we use Red Loctite on our M7 bolt conversion as well. According to Loctite, when the contacting surfaces are prepared correctly, Red Loctite is suppose to add holding strength equivalent to ~20% more torque without exceeding threshold of the bolt.

Tom@TPC Racing

I would like to expand on that one could monitor "Cam Deviation" using Durametric or PIWIS and record these values over time to see if they change and take action prior to a catastrophic failure. Any increase in deviation over time can be from an actuator, chain, guide rails, or even a tensioner. But at least the cam drive system as a whole can be evaluated externally by monitoring deviation(measured in degrees).

PS- we do offer the M7 bolt conversion service for workshops who don't have the machinery and the fixture.

Jamie@dundonmotorsports

Yes the harmonic damper adds a bit of weight to the nose of the crank, but far less than a Dual Mass Flywheel. If you would take a read below before making any decisions.


http://www.dundonmotorsports.com/996-997-harmonic-dampe