DWNDRAFT

The 3.8RS and 4.0RS intake actuator bolts are inherent to backing out, likely caused by engine vibrantion harmonics, again caused by the LWFW. This is well-known and have caused cases of part and total engine damage.

I do not hear about people doing regular inspection routines for these critical bolts? At least it is not discussed?

The right side intake seems to be the that loosens first, but it is also the one that can be check the easiest :
Procedure:
Remove rear bumper + crash bar, exhaust, support the engine rear with a jack, loosen rear engine mounts, remove rear engine mount support plate from engine, lower engine 1", remove RH intake cam cover.
The bolts are clearly marked with laser etched lines across screw head and actuator body, so very easy identify if the bolts have started to loosen (lost tension)
To expose and inspect the remining actuators simply remove the oil lines and vacuum pump.
The screws are 12.9 grade, and following the standard for 12.9 M6 bolts, these should be torqued to 16Nm (not offical number)

I have now inspected a few cars that very running perfectly. When inspecting the screws they have started to loosen, only a few degrees and often with 15-30K miles on them.
There is no way to say when the bolts will become loose enough to be a real problem, but once the bolts pre-tension in lost it will be faster and faster.
16Nm brings the screw right back on the laser marks.



I know that different companies make different solutions to reduce the vibrations effect, I still think inspection is relevant.
I know that Porsche does not officially give a torque number for the actuator bolts. There could be many reasons for that, acknowledging the issues being on of them.
I know that Porsche have revised the actuator at least 3 times. Rev. .91 .93 .95, looking at the parts is see not actual change to the part across these revisions, AND my Porsche service center confirms that the newer revisions does NOT make the old ones obsolete. (so can still be used officially...)

Does anybody else follow a schedule for inspection and re-torque of these very critical screws? If so, what is the millage/hours/type of use experience?

I see no reason to wait until your engine is damaged?

P-Car777

Excellent question and write up DWNDRAFT, would love to hear what others are doing/seeing.
So the 1 and 3 o’clock bolts on your pic show that the laser etching is off have come loose, correct?

limitedslip

Have you thought about adding threadlocker? Blue isn't permanent and designed to prevent loosening due to vibration.

DWNDRAFT

Correct, they will start to come loose like this, usually 1 or 2 bolts more than others. In this stage nothing is affected.
Eventually the cam actuator will be unable to adjust cam angle, and/or one bolt will hit the cam cover, causing engine damage.

DWNDRAFT

Yes, it is ofcause relevant to consider.
Threadlocker requires clean threads, which is not so easy in here.
Even with threadlock, I would come back and inspect, i.e every 10k miles/year or so., untill we know what to expect.

Bxstr

This does not seem to be an issue on the 3.6 cars with or without LWFW, correct? My car is a 997.1 GT3 with stock clutch and flywheel, so I am guessing I do not need to check it. Maybe if I had LWFW then check it?

DWNDRAFT

3.6 does not have variable exhaust, only intake.
I have heard/read of a few none LWFW-car actuator issues, both intake and exhaust (3.8),
but they seem rare.

Bxstr

Thanks, this is great info.

Zeus993

DWNDRAFT - great write-up. I think many of us have heard of this issue and are aware of it but have lacked details. Tku.

Question: what's the total turn around time to check and R&R both sides and put it all back together? Thinking of what dealership might charge for this as I enter purchase negotiations for a 7.2 RS.

I would also think this is something to check when an engine is out for coolant line pining, correct?

DWNDRAFT

With moderate wrenching experince, i.e having removed exhaust and bumper before, I would say a day to get in and out is more than enough.
I doubt if any Porsche dealer will perfrom this re-toruqe (officially atleast), in their book its a none-service item.

I really hope that some of the more experinced RS owners and wrenchers will chime in here too.

Spyerx

I’m not sure this is a good solution just prolonging a known issue.

IIRC ... when BBI made their bolts for this they found the bolts torqued to yield from the factory (ie measure old and new bolt length with a micrometer). I do not recall if they use red loctite but they do use a substantially higher quality bolt (think like arp).

If that iis accurate you’ll never get a good torque on these after they’ve been yielded.

some guys have safety wired theirs.

ranger22

One thing I've been tossing around in my skulls spare room is tack welding the screws in place. Seems like an easy fix that will solve the problem once and for all. Thoughts?

For the record, I did some preventative maintenance on mine and built the actuators to higher spec bolts with locktite and harder bolts to be bolted to higher torque. Why didn't we just tack weld it?

DWNDRAFT

Let me correct that. 3.6 only has varriable intake.
Conclusion is the same though, failures on 3.6 a rare. Different mass/vibration scenario.

DWNDRAFT

The bolts are allready 12.9 grade (stamped on screw head). Tom-TPC Racing and others have done reverse bolt torque checks, and the number seem to be around 15Nm consistantly, below the yield of a grade 12.9 bolts. (around 19nm is 95% of yield for grade 12.9 M6, )
As mentioned, when re-torqing the bolts I get the bolts back on the original postion (laser etched marks) with 15-16Nm, had they been yilding that would be off, as I see it.

cunno

Is this correct I thought the 997.1 3.6 engine had both inlet and outlet variable? 996 engine intake only?