merchauser

timing belt was done june 2016
first warning light april 2017 about 1k later. thinking that was the initial break in stretch
next warning light dec 2018 +6k
next warning light may 2019 +2k

so it seems that its going off at different times and mileage. each time the kempf tool was in the middle of the window and all it took to restore it to the end of the window was 1/4 turn on the tensioner.

SeanR

When I first got my wifes 1990 it had a recent belt change and the warning light kept going off at about the same intervals as yours was and each time I gave it a retension. Finally after the 3rd warning I tore it down to see what was going on. The oil pump gear was wearing down fast. The warning system is telling you that either you have a problem or are not properly tensioning the belt.

Christopher Zach

There are people who know infinitely more about the 928's timing belt, but this sounds unusual. Either:
1) The belt is like a rubber band and is stretching quicker
2) The tensioner is un-tensioning
3) Something else in there is getting smaller (rollers/cogs)

Sounds like something is amiss.

merchauser

what year did they switch from aluminum to steel, and are the steel gears "better"? sean, I assume that the gear looked fine when you did the timing belt?

isn't the reason there is a adjusting bolt on the tensioner for adjustment to compensate for variations with age? isn't that how hydraulic tensioners work? to take up little bits of slack as things wear?

SeanR

I didn't do the belt job on the '90 before to bought it so wouldn't have seen the gear until tear down. Don't know when they changed but the only one you can buy is steel.

Christopher Zach

I would say "Yeah-ish". As I posted above, the 944S (which is not a 928 but has a similar head) has a tensioner with a spring in it so you can set tension by loosening the bolt, letting the spring take up the slack, then tightening down *. You still only retension at 2500 and 15k miles. If you're doing it more often then something is odd.

* And yes, checking the tension with the tool to verify the spring is still good.

FredR

Paul,

The thing that many folks seem not to appreciate is that the alarm system, although reasonably reliable is not exactly a pin point precision instrument and just because it may alarm it does not necessarily mean your belt is low on tension.

Think about it- when the alarm went off presumably you accepted the alarm and the light went out. Did the alarm come back on again? If the belt was genuinely in a state of alarm the thing would go off immediately after you reset it but I'll bet that was not the case. So many times we see threads about the timing belt alarm and how folks called the tow truck because it "went off". If there was a serious problem one would have 32 bent valves. What does it say on the alarm annunciator? Does it say "Tough luck- you now have 32 bent valves" - of course not it says "timing belt service" - in other words have it checked out.

If there is a single annunciation chances are it is a spurious alarm. If the belt is genuinely in low tension and one sees several alarms in quick succession then for sure some checking is required. On my late S4 I had single incident alarms on a couple of occasions- both times I had the car in to the agents to give it a quick check and both times it was fine.

Now of course I do my own timing belt jobs, I set the Kempf tool to mid position and do not have any issues After about 1000 miles I do a tension check and the adjuster takes a minimal amount of adjustment- after that I would only check the tension if I have the cambelt cover off for other reasons like a cam timing check. The difference between mid point and full scale is what?-about half a flat I reckon. The Belleville pack is not just a clever device that corrects belt tension as the engine heats up, it is also a dynamic spring acting in concert with the belt as it tensions and de-tensions - as to how well it does that is a matter of extensive debate but it should not be too surprising if on odd occasion it generates a spurious alarm.

The belt tension alarm is a useful tool in the ammo locker but one should be careful about reading too much into what it is telling the driver. If the belt simply lets go it is not going to do you a whole of good in such situation is it?

merchauser

^^^ I think you may be correct, fred. I was not getting continuous warnings; after a two hour drive, the car was idling in the driveway for a good 5 minutes, during which, the warning came on. got my attention. my first thought was could it be temp related as it was in the low 90's and the car was idling in the sun. next day, driving for a good hour, and the light came on, while pulling into my neighborhood. as mentioned, the kempf tool measurement was in the center of the window. is there an adjustment for the warning sensor?

would a 1990 car have come with the steel oil pump gear? very interested in when they changed materials

FredR

Why would you want to even contemplate recalibration of the tensioner alarm? It is perfectly OK as is.

It should come as no surprise that the closer the belt tension is to the alarm set point the more likely spurious alarms are going to be and your experience supports this. I used to communicate with Jay [Kempf] many years ago. Jay designed his tool to be at the correct tension when the gauge is at the mid point. What has happened is that folks with the factory tensioner tool report that when calibrated against the factory tool the Kempf tool has to be set at the full extent of the window. The presumption is that the factory tool is correct. I know that during development of his tool Jay went to great lengths to get the calibration correct. and he concluded after extensive testing that his tool produced better consistency than the factory tool does for whatever that may be worth.

Regarding the steel oil pump gear I do no know when it was introduced all I can say is that when my cam sprockets were worn and needing replacement the oil pump gear was not and I have the motor from my late 1990 S4 in my current 928 GTS chassis. I thus assume my oil sprocket is steel but I do not know that for a fact.

Wisconsin Joe

Does pressing the button to turn the CWL off reset the alarm?
I thought it just turned out the CWL. The "Belt Tension" on the cluster stays lit up until the car is shut off & restarted.
I know this because I have a PKT and am currently getting the alarm light every now and then (wiring issue, not a belt issue).
I've never had the CWL re-light after cancelling it (accepting the alarm).

Edit to add:

Fred & OP are talking about digital dashes.
I'm talking about the old style.
Different animals.

FredR

Joe,

It is something like 15 years since I last had a belt alarm but as I can recall accepting the alarm takes it off the annunciator and a small warning lamp on the bottom array stays illuminated until the car shuts down then if another condition occurs the annunciator will flash up again and stay until accepted on the stalk. Now the reason I say that is because a couple of years ago I made a spontaneous decision during annual maintenance to replace the belts, I had two pukka items but I did not have a fresh ac belt - went into town to the car souk [Arabic for market] to see if I could find something - I did- fitted it and a week or so later it went twang- all kinds of alarms came up one after the other and pressing the stalk seemed to clear them one by one but I ended up with about three alarm windows lit up and no alternator, no power steering and of course no a/c - I crawled home which fortunately was just around the corner.

If anyone knows better as to how that system works kindly correct that- it is simply the way I think it works and pretty much every instrument control panel I have seen works that way so maybe I am "pre-conditioned".

Rgds

Fred

Wisconsin Joe

Ahhh...

You are talking about the digital dash.

I have an 85 with the 'warning lights'.

Mine only gives one 'warning', the light on the cluster lights up, along with the CWL (!). Pushing the companion light by the HVAC on the center console puts out the CWL, but the light on the cluster stays on until the car is shut off.

I have no idea how the warnings on the digital dash function.

FredR

Joe,

Paul has a 90 GT - a digi dash- same as my GTS and my previous 90S4 . I have no clue whatsoever what is on your baby. Heck I have trouble remembering what I had for breakfast these days.

Wisconsin Joe

Right.

I missed the 'digital dash' part (in part because it wasn't specifically mentioned - but I should know better).

Oops.

davek9

Hi, not going to get into the Stock (tensioner) over the modern Audi unit, my preference is the Audi (with the PK mount).

What no one in this thread has mentioned when that warning light "!" comes on and it's not w/in 1,500 miles of a full T Belt job showing normal settling in adjustment is required.

LOOK at the belt tracking on the Cam gears, that can tell the story of whats wearing out, like: Tensioner running gear (including plastic bushings), Water pump, or the old style aluminum oil pump gear.
The belt should track about 3 to 4mm from the forward facing edge, on Both cam gears, also note the amount of wobble when at idle.

Hopes this helps,

Dave K