taffelman

I use my 1990 S4 as a daily driver to work, driving 130 km (80 miles) a day.

Once and a while I get a "timing belt service" warning in the display. It only occurs maby once a week but always when the engine is cold and if I have been heavy on the gas pedal.

When I erase the message (pulling the handle) it dissapears and does not come back for several days or a week or so.

I have booked a service/inspection at a Porsche shop, but they have 2 weeks waiting time.

Should I take the warning seriously and drop into the workshop and refuse to leave until they check the cambelt for me, or is this probably a warning gremling caused by a cold engine?

BTW the cambelt was replaced by PO a 3000-4000 KM ago.

worf928

The belt must be retensioned after 2500 - 5000 km. (See your owner's manaual.)
A new belt always stretches a small amount after it has been installed.
That warning light is telling you that the belt is too loose.
It takes one hour to check and adjust the tension.
Either do it yourself or pay the shop.
Or, just allow the belt to run loose and wait until it skips a few teeth and destroys your heads.

dr bob

It's a serious warning. Deserves immediate attention, or park the car until it can be cared for. The risk is that a slightly loose belt will try to jump a tooth or two on a sprocket, and then it will strip teeth off the belt. Belt then slips, valves stay open late, pistons run into valves that are open late, piston bends valves that are open late. In the US, budget is $6-10k for a full rework following a belt slip if you take it to a shop for the work.

The car needs to be cold when the tension is checked, so taking the car to your shop and refusing to leave could quickly turn in to the best part of a day under the best circumstances. Instead, offer to leave the car with them until they can get it into their schedule, with an agreement that they won't start the engine until it's fixed. They will get to it just so they can move the car out of the way of other work.

the actual tension check takes less than an hour. If your mechanic is familiar with the 928, it will take less than 30 minutes.

Most Important Things: They MUST have the correct tool to check the tension. They MUST have a copy of a written instruction about how to check the tension. And they must be ready to refill the belt tensioner with oil and verify that it's not leaking.

Way too often, hurry-up "mechanics" will just put a wrench on the adjusting bolt, and snug it up enough to get the light to go out. This is often fatal to the belt, water pump, can gears, and tensioner rollers. It can be fatal to the engine as those parts wear more quickly, allowing the belt to jump and bend valves.

Good luck, and don't ruin a fine car when you can avoid it!

taffelman

Thanks for the fast reply. Guess I am gonna leave her home tomorrow and take her little sister (924) to work :-)

Is there any way to check/retension it myself without the tensioner tool? I've ordered it from 928intl. but it will take a week or two before I get it.

BTW: I got the workshop manual on CD, but browsing through those heavy PDF files is a pain. Does anyone remember wich chapter/page where I can find the retension info?

Sorry for asking all this, but I'd rather use the weekend to fix her instead of browsing for info.

worf928

You ordered the ~$50-70 tool from 928 International? If so, it comes with instructions.

UKKid35

Yes, use the JagEng virtual timing belt guage. It's brillaint (as long as you're not tone deaf).

http://www.jageng.com/sharkbit_2.htm

Bill Ball

Well, yes, Paul Jager has developed an acoustic method that determines tension based on the vibration frequency of the belt. In theory it should be very accurate, assuming belts are all similar density.
The Virtual Timing Belt Gauge

You remove the passenger side (US) timing belt cover to expose the belt. Remove things in the way of the cover:
- fan shroud (some model years are easy - some require removing the upper oil cooler line on the side tank)
- +/- upper rad hose (I work around it)
- dipstick and holder
- distrib cap and rotor
- may need to loosen and slide coil forward a bit

You will see the body of the tensioner under the belt path with 17MM nut and lock nut on the adjustment bolt.

ceedee

gee you guys got me freaked now....
my 83 is non interfering tho , right?

Loaded

I'd be crapping my pants. After what i went through All I can say is STOP! DOnt move it another inch and dont run it tell you checkit out

taffelman

Oh my, something is seriously wrong now!

I started the car today, just to move it out of the driveway, so I could use the 924 to work.

The 928 started as usual but now the display showed a "low on on coolant" warning. I ignored it, thinking I'll check it out later today, and left the car running while I drove the 924 out of the garage. When getting back to the running 928 after 1-2 minutes I found it pumping out huge amounts of white smoke through the exhaust pipe

I quickly parked the 928 in the garage and shut it down. Btw: there was no ugly or unusual noise from the engine, and it ran smoth as usual.

I've been thinking about it for an hour now while driving the 924 to work, and this is my guess:

The PO have tensioned the cambelt too hard, and now the waterpump is broke, and I am lucky to have stopped the engine before the cambelt has slipped or at least any valves has been bent.

Does this sound like a decent explanation or am I looking at a blown headgasket?

Or could it be something else?

BTW:The engine has only 88.000 km (53.000 miles) on the odometer, and was last serviced about 3-4000 km ago.

littleball_s4

I'm sorry.

The car is trying to tell us something, it's just I don't know what it is. Simptoms doesn't match to me.

What was the temp reading?

littleball_s4

Wait, perhaps you are right.

The w/p is not working properly, because of excess of tension in the belt, the car overheated as you taked it home, somehow you didn't notice (bad sensor or something) and you bent the head and/or blew the gasket. Then, in the morning, water was low (it's normal after overheating, it escapes through the cap or gasket) and you are burning oil.

The shop should give you an answer.

taffelman

I dont think it is burning oil.

As far as I remeber white smoke = coolant and dark smoke = burning oil.

When driving it home yesterday it did not overheat or smoke at all. I checked the temp gauge, and I would have seen this smoke in the mirror when parking, but it was not there.

This smoke was very white.

The question is: Is it usual for the car to smoke white when the waterpump brakes down?

Vilhuer

Only if non rotating water pump kills head gasket.

littleball_s4

Nah. White smoke= oil. Dark smoke= unburned fuel. I don't know what happens when you "burn" coolant, if it's even possible. Probably nothing or perhaps vapour like in cold days. If the cloud was very white it is oil.

It's not unusual that the overheat damage shows up the morning after. When everything is hot the seals are ok. So you could have very well not smoked the evening before.

But if you say temps were ok... Then I don't know.

The only sure thing is: big amount of white smoke will require pulling the heads for fixing. It's the head, or the gasket, or a piston or a ring.

Best of luck.