Porsche Enthusiasts Club Forum

Here I am again! Sorry about all the postings but I've just bought my car and have a raft of questions....

Went out in the car last night. After about 20 minutes the "toothed belt service" message came on, then it kept coming on, sometimes a few seconds after cancelling it.
I parked the car in the garage and left it.

Now the previous owner said he replaced "everything" when he did the belt recently. Let's assume that he did, and all parts are new.
The belt tension adjuster is a threaded bolt with a locknut on it. Just a thought.....has anybody adjusted their cam belt after the "toothed belt service" light came on? if so how much did the adjuster need tightening? One full turn...half a turn?

Yes a new belt will stretch in first few hundred miles. It's an important maintenance instruction to check and retension as necessary after 1500km.

If belt snaps or slips you could wreck engine very easily. Happened to new 928 owner recently after his belt change was apparently bodged by a well known and usually well regarded Indy.

The belt may only need 1/4 or 1/2 turn on adjuster for correct tension, but don't adjust yourself unless you have the brilliant Kempf tool available in UK from John Speake.

If you still get tension warning then the PO may simply have failed to reconnect belt warning wire, or more seriously made a mistake in installation such that belt not running true, tensioner mounting bent etc.

If you don't want to check yourself then drive carefully to reputable garage for check. Warning the cambelt could snap simply at idle so if belt install dodgy this is risky.

If belt is just stretching as normal for new belt then tension warning would normally only trigger after hard acceleration/kickdown.

OK well I've just removed the LHS cam belt cover and can see the belt going round the LH camshaft pulley. the belt looks new and I can see what looks like the water pump, and that looks new too. The belt is central on the pulley.

I need to turn the engine to TDC and then check the tension. I'll order one of those tools as advised above.

I've removed the distributor top, is it OK to take off the rotor arm assembly too? This would make it easier to get the belt cover back on!

Also can anybody tell me where the belt tension sensor is located...there's a black wire going through the cover just behind the top of the dipstick tube, is that it?

Assuming you're using LHS in the conventional sense, i.e. based on looking forwards from inside car, then you'll find it's much easier to remove the RHS cam pulley cover. No need to remove rotor arm, just the distributor cap. having said that the rotor arm is just held in by allen bolts but they can be tight if not removed before so better not to risk rounding one if you're not trying to change rotor.

The crank has to be at 0 and the timing marks aligned on cam pulley (notches lined up) to be at TDC No 1 (crank rotates twice for each cam rotation).

Yes that's the warning system lead. It could be it's just come loose from its terminal if it was disturbed during the cambelt change.

There's an excellent guide to troubleshooting the warning system (assuming tension ok, and warnings are spurious) on the Nichols Tips page (928 bible) here:

http://www.nichols.nu/tip016.htm

I was looking at the engine from the front, so did remove the RHS cover as you suggested.

As the engine is supposed to only be turned clockwise, would that be clockwise looking forwards from inside the car, or looking at the engine from the front of the car?
If it's the former then I turned it the wrong way......

You turned in correct direction - it's clockwise as you face engine.

The LHS and RHS are conventions defined from inside car to avoid confusion. Also means don't have to use "passenger side", "driver side" which of course differ by market.

Thanks for the advice re engine rotation. The same as my 1932 Standard Nine then! A bit harder to turn with a spanner on the crankshaft nut than the Standard though.

The belt looked OK for tension, although I did not have a tool for checking it. With the engine at TDC the top run of the belt (round the camshaft pulley) was tight but there was enough slack in the bottom run to turn the belt about 45 degrees using my thumb and first finger.
Clearly it's not about to fall off the pulleys, but I've ordered the tool suggested for checking tension.

I'm wondering, maybe the last owner when he replaced the belt did not rebuild the tensioner. Can this be removed and rebuilt easily if that is the case? I've also downloaded the procedure for checking the warning system and will go through this later.

tbh I've not done a belt change, but planning to do next one when it's due.

However I'm pretty sure that removing the tensioner to rebuild it requires similar procedure to replacing the whole belt i.e. locking flywheel, removing both cam covers, removing all ancillary belts.

I'm sure someone more knowledgeable here will correct me if this is wrong!

You can't check the tension by feel, you do need correctly calibrated tool.

When you get the tool you will need to adjust tension to high side of window for your 32V engine (this will make perfect sense when you receive tool and the excellent instructions which come with it).

With a correctly tensioned belt there is a short cut to checking tesnion with no disassembly required, which entails pushing a drill bit through hole in pulley cover and marking belt deflection for known thumb pressure. Also some 928 owners swear by a sound file available on internet which lets you 'tune' belt to correct tension. If you join the 928.org.uk list and ask then several members will know what you mean and give you the link.