siscogts

Hi!
Yesterday I did last TB tension check for this belt, as i't 4 years and one month old , I did 13 k kms ... soon a change is due.
It was my first DIY tension job,actually not complicated.Kempf tool is practical, essential.
Put tension on the "high side" of the kempf window - range, I was told to do so on 32v engines.
First of all, I did tension check cause I saw the TB tension warning on instrument cluster twice, I realized then it appeared in the same place: a very hard climb , during 2nd-3rd gear change at 3-4 k rpms....
I think warning system wirings need a check.

Now the pictures:
tell me if cam timing can be considered between specs and conditions of sprockets, it seems one need coating soon.


















passenger side sprocket










driver side sprocket





Any suggestion is well appreciated.

Mrmerlin

from the pictures the timing looks good,
the belt is tracking as it should,
the cam gears are showing lite wear,
so at some point it would be good to remove them and have them coated.


To check the timing
the engine must be cold and set on TDC,

the belt should be adjusted so the kemp tool pointer should indicate to the top edge of the window for the 32V engines.

NOTE spin the engine over a few times to verify this adjustment your looking for repeatable results

Other things that can cause the warning,
A loss of oil in the tensioner, I suggest to use STP oil treatment for tensioner filling.

A migrating waterpump bearing, this will cause loss of belt tension.Usually found in rebuilt pumps.

Worn connectors, loose wires,try some deoxit 100.

A missing preload washer on the tensioner pushrod.

Worn tensioner pivot bushings , or bent pivot bolt

Broken cam snout due to over tensioning of the belt run, or prying on the cam gear to remove the pulley

siscogts

Thank you, you are an encyclopedy with legs.....
Within 1 year i will change belt roller, pump....so i will remove sprockets to recoat them. Pump, rollers, belt, tensioner($$$$) were purchased new from the porsche center, no cheap stuff like crap water pumps on ebay . Checked tension 5 times (10 rotations). Wiring ok(seems ok). The rest is OK, except i had to fill the tensioner with a lot of oil. Maybe during that climb the tensioner works badly if short of oil...JUST during that climb. Weird....

ROG100

Remember that the de-tensioning system is a very old but reliable design that cannot keep up with dramatically changing conditions that modern tensioning systems can.
So seeing a warning is not unusual - as already said check and set everything and keep driving.

Imo000

Why would you want to change the belt with so little kilometres? The 5 year replacement interval was invented by the internet and mostly this forum.

Captain_Slow

My S4 used to throw the warning light when mashing the pedal and just at the point of the abrupt upshift around 4000 rpm. It hasn't done it as frequently (seems less sensitive) recently. I also have the Continental (gasp!!) belt that the PO had installed. I have two hypotheses about what is causing the light to come on:

1. The Conti belt stretches elastically as the rpms climb. Then during the moment of the shift the belt slackens as rpms decrease. I've observed the light does not come on during the rise in rpms. It comes on just as the shift happens. I may have too vivid an imagination but it seems that the belt looses a bit of tension during the moment of the shift...while the belt elastically contracts. Once the light comes on it will stay on, but several times I have pulled over immediately, turned off the engine, restarted, no light. I imagine that this period of reduced belt tension and elastic recovery is extremely short...and just enough to throw the light, which is, by design, triggered at a non-critical reduced tension (what good is a tension warning light that comes on at the moment disaster strikes?). I think the reason the light is coming on less frequently is due to the Conti belt having stretched slightly and permanently, resulting in less elastic rebound during the upshift.

*It's also possible I'm unconsiously not driving the car as aggressively, making the upshift less abrupt (hard). I don't baby the car and under all moderate to spirited driving situations the light never comes on.
*KLVA installed the Conti belt and about 2000 miles later I checked the tension with KLVA's guidance. After the first time I witnessed the light come on I tightened the tensioner 1/4 turn, so we observed the tension to be about a millimeter beyond the high side of the Kempf window. We left it this way due to the Conti belt's known tendency to stretch.

2. It could be the tensioner connection. My S4 has the older solid copper ribbon (Your GTS has an upgraded wire connector???). This copper ribbon is partially corrugated (alternate ridges and grooves) to give it some ability to flex (or expand and contract with temperature variations). Over time the ribbon becomes brittle and cracks. If contact is lost momentarily at the split it would trigger the light. I think this would trigger the light randomly (or at least under more circumstances than the hard upshift described above) so I tend to think this is not the cause. However, I have purchased the wire connection upgrade to replace the copper ribbon and will install it when it's time to change the water pump and belt again.

Do you know what brand of timing belt is on your car? If not, I'd turn my attention there as well.

siscogts

Captain, good point.I have a porsche/gates belt.

Imo000 :I think that 5 years are enough for this belt, I prefer to be safe than sorry( and poor).

Anyway,30 minutes ago,I did the same climb, I repeated the same scenario : no warning.
2 things have changed: tension(less than 1/4 turn) and oil in the tensioner.one of this solved the problem, possibly......

Francesco

Imo000

What makes you think 5 years is enough, what do you base this decision on?

ROG100

I would be more concerned about the de-tensioner loosing oil. Did you put some RTV between the lock nut and tensioner? Oil can leak through the threaded section where the tensioning bolt goes into the body

siscogts

tensioner is not loosing oil, nor "is sweating".

5 years are a good time for my experience to change timing belt, I changed the belt on my company car (Subaru Forester) after 7 years and 207 k kms(factory says 5 years or 100 k kms) and feeling " unsure/unsafe " when you use a car is something bad and wrong at the same time.I tempted fatemany times for too much time so,despite the low mileage ,I prefer to be safe, more than sorry.
Then there's a modified Murphy's law:" if you think the timing belt in your 928 will give you problems , the belt will do".

Anyway, seriously: I think a 928 does not deserve maintenance based on luck.

GregBBRD

Reading your post, it appears that you have already decided your course of action, so I'm somewhat confused about why you are asking for opinions....

However, I'll give you mine....

Forget replacing the belt. It doesn't have enough mileage or time to give it a second thought.

"Recoating" the gears is a joke.....a "used car lot" approach to a repair. There's not a dry film coating that can stand up to the rigors of a belt rubbing on the surface. When the gears completely wear out, buy new gears....the new gears are "light years" better than the old gears, in terms of material and coating.

Correctly tension the belt, bleed the tensioner, put the covers back on, and check it again in another 20,000kms.

hacker-pschorr

Where do you come up with this stuff?

When my father purchased his 81 back in 1991 (or 92) the dealer told him 5 years and / or mileage, whichever came first.

So unless my father is somehow Al Gore, not sure how he would have picked that up over the internet.

siscogts

I have not decided course of action , but many eyes can see better than my two.
Maybe you can see something wrong on the belt teeth , some weird wear , some misalignment. So I can re-think about the idea I have of the belt and timing sprockets residual life.
In fact you wrote that recoating is a mild remedy (Others told me it is good enough , especially for my mileage/year...and I thought it was a good idea, especially if I think at the frightening price of those 2 sprockets), that 5 years means not the belt is gone, that I have not an impending sprockets failure.....

anyway "5 years" is what rubber timing belt producers and car producer usually suggest for a change .

Francesco

mark kibort

'
I dont believe the belt stretches by any measurable effect. ive run dyno runs that dont seem to indicate a problem.. Ive had small changes of timing that does effect HP and corrected that with proper, logical cam timing.

Ive run the conti belts for 20 years with no issues. tension stays put for about a half of a season of beating the snot out of the engine

4 years but only 10,000miles is not enough tiime or wear to worry about the belt. after all the factory recommeneded 60k miles before changing it.
if it were me, i would change the belt after 5 years if you had 60k miless on it, or 7 years just for age.

the tension light doesnt come on for belt stretch. it doesnt stretch that much. it comes on because of vibration near the contact points of the tensioner warning actuator.

the oil in the tensioner doesnt do anything with tension . it transfers heat from the engine to the oil to the tensioner washers which expand, flatten and change tension.. thats a very forceful metalurgic force. nothing to do with the tensioner when hot or cold and running. no oil and it just takes longer for the expansion

why are you concerned with the oil at all? yes, you can loose the fluid, but the system still works. without fluid, it just takes longer for the tensioner washers to flatten and reduce the tension as the engine block expands.
over tension is the cause of most of the wear issues i think... mine look amazingly good, and they are 30 years old and have 15 years of some pretty hard racing on them. However, i wouldnt be concerned with those pulleys.... they seem like they are wearing on the tops, so i would keep an eye on them. Ive seen bad ones.... they are ugly. (usually the old aluminum types) they get worn out to the point that the gear teeth are going away like worn rotors with a huge lip.

siscogts

I feel "pampered" and reassured , many 928 experts gave their opinions and many made rethink me about the belt: sometimes I read about people scared about this belt, I start to think that someone behaved like a baby with the boogey man.Me included.

@Mark kibort7 years is alot of time, considering you're talking about Conti belts and not race-spec ones .

So I can posticipate the belt change? everyone sure?

Francesco