RKD in OKC

Pull the cam gears and check the alignment hubs and key slot on the ends of the cams. Ask Sean R how I know...

LT Texan

Ditto

Hilton

This - conti is the most common belt used in the uk, and they do stretch with age.

Leon Speed

OP needs to get into touch with this guy Roger in Texas, he will hook you up

69gaugeman

I just have to re type this so I can make sure I have it right.

"I just got an alarm that something changed in the factory timing belt system, so I wish I had changed it to something that would not give me any indication that there was a problem"

Is that about right? Jesus.......

Captain_Slow

Under hard acceleration my S4 (auto) tension light sometimes comes on. The belt was changed recently by a fellow rennlister about 3000 miles ago in Feb. 2013. It is a Conti belt. I tightened the belt a quarter turn just before Frenzy. Light came on again under hard acceleration (right at moment of hard gear change. Last week myself and the rennlister who installed it pulled the covers and checked the tension. It's slightly tight (because of my quarter turn), just outside the window of the Kemph tool. We decided not to loosen it as the belt will likely stretch. Belt was perfectly centered, tensioner not leaking. I do like the warning system. I also wonder why Porsche stuck with the tensioner/warning system for 18 years. They had plenty of time and experience to determine if they should ditch it.

RKD in OKC

My Toothed Belt warning came on several times, checking belt tension found the belt well within spec, even rebuilt the tensioner. Still came on occasionally and belt was at proper tension. Then the end of the driver's side cam broke off at the keyway where the alignment hub is keyed to the camshaft. It warned me. Neither myself or 2 very good 928 mechanics thought to check the cam gear mounts.

If your toothed belt warning goes off and your belt checks to have the proper tension, check for other things!!! Pull the cam gears and inspect.

Lizard928

Richard,
Agreed, but conti belts will stretch especially when hot and set off the belt warning system when nothing else is wrong. I will never use them for this reason.

JEC_31

I believe that it is a trade-off: switching from Porsche's insane Rube Goldberg belt tensioning system with it's 47 (IIRC) possible failure points to an aftermarket system engineered for robustness by using Japanese mass-produced technology with a handful at most of possible failure points, each of which are unlikely. All that is lost is the tension warning light, itself a common failure item causing undue pucker moments and as others have pointed out not impossible to replace, while the reliability gained is priceless.

I will never forget my befuddlement at the leaking gasket, the pile of bimetallic washers with their tiny range of movement, the undersized bearings, the sheer delicacy of the entire system when I refreshed the 86.0 I used to have. The belt itself is not to fear - it's the tension system that kills 928s.

Tom in Austin

Yeah, so what was the PKensioner Black system exactly ?

Imo000

Where do you get your data from? I haven't heard of a tensioner failing on the 928. Quiet the opposite, when my water pump siezed, the belt warning went off way before the temperature was even close to red. It saved my engine because I didin't ignore it. The incident was documented here with pictures that would give anyone a real pucker moment.

jeff spahn

I am second on the list if Alan makes one of these.

JEC_31

Just forum chatter, no real data. I suspect many of the belts that stripped teeth and the belts that mis-aligned and rubbed into covers may have been the tensioner letting it happen.

When I did mine the system was falling apart and ready to fail. I ended up replacing everything, this was before Porken developed his aftermarket solution.

That is a great save, and all the more reason to incorporate the warning light into the aftermarket solution.

With due respect to the original design, it does work exactly as intended when kept fresh. Rube Goldberg machines do run, but they need frequent preventative maintenance to keep running.

SeanR

I've seen many of the factory tensioning set ups fail, to say they don't happen is to show yourself to be a liar and a fraud. Way more failures on the original set up than water pumps or gears. Keep in mind that that thing bolted to the block is only part of the tensioning system, there are bushings, rollers, pins etc. And as said, if all if it isn't fresh it will fail.

The PKT might not have the warning system (yet) but it has 4 parts not including 8 bolts holding those 4 bits on there.

mark kibort

im still using the conti belts and havent seen any issues in the 17 years of racing with them. i always measuring the tension, and if you remember, even made a crude way of checking at the track, without removing covers. usually that light comes on for other reasons. usually having to do with the contact circuit in the warning system.