tension belt warning light

Niel68 · 02-23-2008, 05:50 AM

Hello all,
I'm new here and also new owner of 928 (2 months).
It's an S4 My88 and I'm in Italy. it was in great condition, but after buy I preferred to have a complete check, with cam belt and water pump change.
But after these works the tension belt warning light started to light on frequently. When it turns on if i stop and restart the car it went off and I can run many miles before it light on again. It could happen after acceleration, but also after slow driving. We checked the tension and it is ok. Only strange thing was that checking for possible air bubble in the tensioner oil, it seems that no oil was in. Do you think that I need to remove the whole tensioner to check? Could it be only a problem of wrong signals?
Any help is appreciated before unbuilding again the car.

Incognito · 02-23-2008, 06:07 AM

The wire to the sensor sometimes gets loose on it's connection causing false signals. Check to see if it is tight.

Damstrom · Damstrom's Garage

Best thing is to order the Kempf tool $45 USD (or about 20 euros

). Mine came on similar to yours on my 88 and it turned out it did need tensioning as it was not in the spec window. I'm relatively new to 'wrenching' on my car so this was a good project to get to know your car better and was done in an hour...every satisfying too and not extremely complex. Demistyfies the car a bit too.

Kempf instructions come with pictures too and there are many write ups (ex Nichols tips). BTW I did not remove or drain my radiator making this job easier. The fan shroud does come out and just takes a little patience and moving things around after loosening the power steering reservoir.

Ciao!

Danglerb · 02-23-2008, 08:17 AM

What sort of complete check with cam belt and water pump didn't include rebuilding the tensioner? I would question every bit of the work that was done.

low miler · 02-23-2008, 09:44 AM

Let me ask you this, did the warning light start coming on right away after the timing belt change, or was after some miles had been put on the new timing belt before it made it's appearance?

The reason I ask, is that having the timing belt re-tensioned exactly 2500 miles after a timing belt change, is just as important as the entire timing belt change itself.

My guess is that if you have the timing belt correctly re-tensioned now, the light will no longer come back on. I'll put $5 on that guess is correct!

I'd wager more, but unfortunately, that's all I've got on me right now.

Best of luck, Todd

Danglerb · 02-23-2008, 10:31 AM

I don't think the mileage is critical, the belt stretches a bit after its on, could be more time than miles. My guess is people pick a number, long enough that most of the stretching is done, but not so long as to present much risk from driving with lower tension. I've also heard two weeks, or 1000 miles.

I'll ask Greg about it next week since my TB etc. was done a couple weeks ago and the motor is setting on a pallet waiting on a few other last things before being installed. Maybe it should be retensioned before putting it in the car? Might be curious to check it anyway, see if it has stretched while just sitting.

SeanR · 02-23-2008, 05:48 PM

If there was no oil in the tensioner, they either did not rebuild it, or rebuilt it improperly, both are bad news and need to be addressed. Sure, a car can run many years with one faulty, but why would you want to when you have $5k plus of issues at stake.

Pulling the tensioner is really not a huge issue considering what is at stake and doing a rebuild of one is really simple. Clamp, boot, cleaning of the washers. The time consuming job is making sure you have the cam gears in the proper position and the retension. Nice thing about the later tensioners is the fill nipples for the oil, the early ones don't.

Take the time to have it done properly.

SeanR · 02-23-2008, 05:50 PM

Quote:

Originally Posted by rogue

Why does it have to be retensioned exactly 2500 miles after timing belt change?

The ones we've done here in the DFW area were all rechecked at 1500 miles. The belt will settle and does stretch a tad bit. I'd not chance the light being the only warning sign. Sometimes the light won't work correctly and a person has no idea that the belt is loose.

Checking tension is a 30 minute job.

Niel68 · 02-24-2008, 12:55 AM

Thanks everybody for your reply... I think I have found a good forum for 928!

Quote:

Originally Posted by low miler

Let me ask you this, did the warning light start coming on right away after the timing belt change, or was after some miles had been put on the new timing belt before it made it's appearance?

Before belt change I had no problem (about 300 miles), after the change the problem started immediately. The tension was also re-checked after the first time light went on. I also have some doubt about the work done: why he didn't rebuild the tensioner? For sure he changed the Tensioning roller, roller, carrier for tensioning roller. He is an expert mechanic for old Porsche (he is sixty and worked in Porsche), but probably more skilled in 911 then transaxle.
But now I have to problem:
1) try to indentify possible causes of this problem, so I can check work to be done.
2) understand is it is safety to drive till he will not solve the problem.

In the meantime I'm trying to check possible electric causes by myself, and also to refill properly with oil the tensioner.

DanielDudley · 02-24-2008, 03:27 AM

No, it is NOT safe to drive your car. If the belt slips, you will have a very costly repair to replace bent valves. Can you afford to take a chance ?

Find a good 928 mechanic. They are few in number to 911 mechanics, but essencial to keeping a 928 happy. 928s are very reliable cars, but only if serviced properly. A little patience now will pay off in the long run.

Danglerb · 02-24-2008, 11:54 AM

Timing belts fail for two main reasons, neglect with eventual parts failure, and repairs improperly done.

If you could find someone that really knows the 928 well, and TB and WP issues specifically, they might be able to look over what was done and tell you if its OK or not, but it might be more practical to just do the work carefully again following one of the guides.

Chances are fair that your mechanic may have reconnected the tension sensor that was previously disconnected or bypassed.

Niel68 · 02-24-2008, 11:54 PM

Quote:

Originally Posted by Danglerb

Chances are fair that your mechanic may have reconnected the tension sensor that was previously disconnected or bypassed.

This could be possible. The old owner made also some other change like
disconnecting the supplementary air pump and modifying fuel pressure.
I told that my mechanic is more skilled in 911, but he knows 928! Maybe he didn't rebuild the tensioner: this was his fault. But I think that now he understood he made an error, and he want to do it now.
Let's see if he can solve the problem... Otherwise I need a new one!
Further my intention is to start to try to make some work on my car by myself, but I don't want to start with a so dangerous/diffucult matter like TB.

Danglerb · 02-25-2008, 02:00 AM

Do you or your mechanic have a set of the 928 Workshop manuals?

I suggest buying this manual for the timing belt even if you have the workshop manual, it is very detailed and leaves nothing out.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=190200402522

Niel68 · 02-28-2008, 07:34 AM

Thanks for all suggestion.
Can someone give me a list of all part which should be changed during a cam belt change? I saw some kit online but I'm not sure if they have all parts that is better to change.

Danglerb · 02-28-2008, 09:08 AM

Some items can be inspected and only changed if signs of wear are found. Here is a link to a typical kit of parts.

https://www.928gt.com/pc-2177-1403-timing-belt-water-pump-kit-87-95.aspx

Depending on wear you may also need to replace the Cam gears.

http://www.pelicanparts.com/cgi-bin/PartsLookup/search.cgi?command=show_page&Catalog_Name=928_USA_87_91_KATALOG&Illustration=103-05&Line_Item=6

Niel68 · 03-03-2008, 02:27 AM

Update.
I started some DIY job waiting for mechanic to be free to work on my car.
I have checked the tensioner and oil was in, but for sure it was not rebuilt: the oil inside was full of dark parts (I think metallic). So I drained it all and refilled with new 75W90 oil. I check for oil loss, and it seems ok. Then I switch on the car for 10 minutes, and then I started on road for a check. I drove 30 minutes without problem (under 4K engine turns), but then the light came on. Stopped the car, drove to home for 10 minutes and the light came again on during reverse shift to put it in box. For me is always more strange.
In the meanwhile I have ordered the Kempf tool, and the book on TB change.
Just another thing: my car has only 100K miles, this is it's 3rd TB change.

SeanR · 03-03-2008, 02:37 AM

Not sure if it matters, but I just use 15/50 engine oil in the tensioner. When you emptied it and refilled, did you have it apart and off the car?

Niel68 · 03-03-2008, 03:55 AM

I choose W90 following a lot of internet guides. No I din't removed it, just drained and refilled. Do you think that doing so I didn't drained all the oil? If yes, it is possible to remove tensioner without removing also the arm and rollers or re-tensioning the belt? At this moment I don't have the Kempf tool.