Porsche Enthusiasts Club Forum

How is the belt tensioned my warning light comes on with mild to firm acceleration and also when mild revving from tick over.

Hi

You CANNOT do it yourself as you need a gauge to set the tension... also if the light is coming on the belt has either stretched or gone soft , which can be caused by being soaked with oil (not uncommon)

It sounds like you need a NEW belt (and possibly water pump)

BUT.... WHEN was it last CHANGED ?????

They must be changed EVERY 4 years (no matter what the mileage)

All the best Brett

Hi potdog what MY is your 928? All but earliest have interference engines so don't run engine till belt changed.

As Brett says you need tension gauge (Kempf tool is cheap and easyto use), but unless you have just changed belt and it's stretching within first few hundred miles the belt needs changing, and/or there is problem in belt system which will be apparent on inspection when you strip front of engine (which has to be done for belt change anyway).

When belt is slightly loose it will trigger warning when you mashthe throttle. If it's warning on mild revs it is dangerously loose and needs urgen attention.

Just had belt changed at Porsche specialist only done 2 miles . Never had a problem before when first purchased car had water pump and belt changed in 2009 and drove it hard .

When fitted correctly it won't stretch within 2 miles to extent of triggering warning!

The specialist needs to check their work as something is amiss. Just tightening the belt with tensioner is not a solution (unless they simply overlooked tightening it to correct tension in first place, perhaps because they did not have either the Porsche factory tool or the Kempf tool).

Hi

As Adrian says...the specialist got something drastically wrong..... I am not sure I would even drive it until they have recovered it (at THEIR COST)..on a trailer or recovery truck and put right whatever they did wrong....

Assuming they did the belt correctly (they didn't) the earliest the light may come on is around 1500 miles when it may need re-tensioning...

Which specialist was it ?

Just to emphasise how important this is..... if that belt jumps some teeth and its an interference engine...it will bend ALL the valves as a minimum, and cost you THOUSANDS

All the best Brett

Forgive me for hijacking, but is it only the 32V engines that are an interface engine or are only the 4.5 V8s a non interface unit?

As Brett says. I wouldn't drive or start the car up. Call whoever changed the belt and have them come and collect it. Something isn't right.

When l bought my 928 S4 l had to drive it home about 100 miles.

The "TOOTHED BELT SERVICE" warning light came on and every time l pressed the button to reset it, it came back on again within a few miles.

I was sure the car was about to fail, but l got home OK and took it straight to a local specialist.

He said the belt was not about to come off or jump a tooth. He said the hydraulic tensioner was empty and needed adjusting for the correct tension.

By the time he had done that, and replaced the leaking sump gasket, l had a bill for £1,000 and l had only owned the car for three days.

But he did say it was a good one....and that the engine mounts needed changing.

No such thing as a cheap 928 holds true then!

I believe they are all interference engines, if that’s what you mean? I certainly wouldn’t like to take the chance if the piston smacking the valves if the belt failed in a V8. The price of a belt change compared to new valves etc. is quite scary.

All 32V 5.0L up are interference.

All 4.5L are non-interference.

With the 4.7L depends on ow early or late they are!

That,s interesting Adrian, I thought my 1980 S was an interference engine? does it depend on the month in the year.., is it as crucial as that ?

Ken.

Hi Ken,

If it's a single distributor it's non-interference.

I don't know if you can go by build month, but there are definitely otherwise identical models which differ on being interference or not, depending on engine number. It also depends on whether they are Euro/ROW or US spec just to make it more complicated!

H,mm,.. thanks Adrian yes, mines single distributor. The car was delivered new by AFN Chiswick, in March 80. So many conundrums ? Iv,e always erred on the side of caution and changed the belt by time, rather than miles, as it does,nt see much mileage.
It was changed last July and since, it,s only done under 400 miles

Ken.