Cam Position Deviation on 996TT

Hello, My 996TT has developed an intermittent rattling noise. It comes and goes suddenly and it is hard to pinpoint what conditions cause it. If anyone has experience with this issue, I would really appreciate your insights. So far, I have gathered the following data and observations using the Durametric tool: • Actual Angle of Camshaft on Bank 1 and Bank 2 are similar (see below). • Cam Position Deviation on Bank 1 and Bank 2 are very different (see below). • Fault Code P0021 (Porsche Fault Code 325) - Camshaft position with respect to camshaft bank 2. • When I activate the Valve Lift control test there is quite a bit of noise, and it is more pronounced from Bank 2. (I tested them individually by disconnecting the Valve Lift Solenoids on either side). • I disconnected both Bank 1 and Bank 2 variable valve timing solenoid and there was no change. From what I have researched the issues could be caused by: • Bank 2 intake camshaft has loosened • Bank 2 intake camshaft sleeve has rotated causing the blockage of the oil passages • Bank 2 camshaft oil housing is worn • Bank 2 chain has stretched • Bank 2 chain tensioner has collapsed • Chain ramps are worn out • Intake tappets are sticky or defective I will pull the motor in the next week and inspect the cam timing, tappets, chain guides, etc. In the meantime would really appreciate any insights from anyone with experience with these issues. If this is of interest to anyone I will post my progress. Thank you, Jeff

Hi Jeff, Where did you get to with this issue? I have similar symptoms. I am going to do some logging on Durametric to get a better understanding.

In case anyone is looking for a follow-up to this, I posted an update here on Pelican Parts - P0021 and Noises

Hello, I am writing to provide an update and conclusion on the issue I previously mentioned in the above post, in order to contribute to the collective knowledge on the topic of VarioCam issues in 996 Mezger engines (996TT/GT2/GT3). Background: My Porsche 996TT was experiencing a rattling noise at idle and while driving, particularly when the VarioCam high-lift was activated. In addition, there was reduced power, a check engine light, and fault codes P0021/P0022/P1349/P1358 and Porsche Fault Code 325, indicating excessive cam deviation as per the Durametrics tool. The noise changed depending on oil pressure and temperature, and the issue showed similarities to what the BMW community encounters with some VANOS designs when they fail. To get to the point, the Porsche 996TT/GT2/GT3 models utilize cam phasers similar to those in the BMW M62TU engines, typically found in late 1990s BMW 740i vehicles. These cam phasers are prone to aging and wear of the seals used in their construction. Thankfully, after establishing the connection between the cam phasers used in 996s with the Mezger engine and early BMW VANOS systems, I contacted Chris at Dr. Vanos in Austin, Texas ( https://drvanos.com ). Chris was able to rebuilt my cam phasers, which resolved the issues. Recommendation: If you own a 996 with a Mezger engine and you need to open the top end for any reason, I highly suggest having your cam phasers rebuilt. As these cars age, just like the BMWs, it is only a matter of time before the seals in the cam phasers wear out. Although I have heard of very few cases of this happening in 996TT/GT2/GT3 engines, I suspect we will see more occurrences as time goes on. Here are the parts numbers this applies to: 996-105-051-73 - for the 996TT/GT2 996-105-051-93 - for the 996GT3 996-105-051-95 - for the 996GT3 I cannot confirm if there is a difference between the specific cam phasers used in these models, but based on the information I found, the cam phasers in the 996TT/GT2 can adjust the intake camshaft by 15 degrees, while the GT3 cam phasers provide an adjustment of 12.5 degrees. Please feel free to reach out if you have any questions or comments. Jeff