amorgan

Hello all.
Having recently purchased a 1989 964 c4 i have come across my first problem which i am sure a lot of you guys can help me with. The car was a model for the japanese market so the manual does not make any sense to me and while driving yesterday the alarm buzzer went off the the 4wd/abs warning light came on. What i wanted to know is whether i can continue to drive the car and what experiences members have had and what has caused this.
Thanks

Andy Roe

OK, firstly, welcome to the board!!

I'd initially check a few things. Is your brake fluid low? The ABS/Traction control system uses this fluid to charge up it's hudraulic sytem. Secondly, it could be something that happend to me on my old C4 which turned out to be a faulty voltage regulator on the Alternator. As the battery became flat, the car was not getting any power. I wouldn't drive it until you know what the problem is! Something could have failed with the braking system, which might cause you problems when trying to stop the car!!

Good Luck!

Andy

amorgan

Hi Andy not too far from me. I am in the Dartford area. I will check the brake fluid then. obviously i want to get this sorted asap, who do you use to do work on your car around our area.

Andy Roe

No worries! I use HP Motorsports which are in Stratford. I'd recommend them - it's always the same mechanic who has worked on both my cars which I believe is a nice personal touch. He's also collected & delivered my car back to me in the past. I think they may be moving nearer your neck of the woods soon too! The chap who works on my car is call Joe & his number is 07811194540.

Andy

Andy Roe

Oh, forgot to say that when checking the brake fluid level, the engine must be running!

Computamedic

Hi, and welcome!!!

I also have an '89 C4 and suffered exactly the problem you have for almost a year before I discovered the cause.

There are (unfortunately) many potential sources for the cause of this problem and you need to analyse some of the symptoms before you can hope to identify the cause.

I am assuming that the problem shows up as both ABS and PDAS warning lights together with the main warning light and gong come on together. Does the alarm come on soon into the drive or can you drive some way before the alarm?? Does it happen ONLY when moving or does it happen sometimes when standing still with the engine running???

Some of the dynamic causes can be faulty wheel speed sensors or failing accelerometers (they can get stuck!!). Unmatched wheel diameters can cause a problem but, to be honest, it's pretty unlikely to be that. It can also be that one or more of the ABS relays can cause problems. It's worth getting a fault readout from a Bosch Hammer but treat it with a pinch of salt as it may turn out to be a red herring!!! The hammer didn't give a clue to my own problem.

My own problem turned out to be (thank you JZ Machtech) badly arcing ignition coils and distributor caps. The arcing causes the ABS/PDAS computer to get confused and it will generate the alarm. Have a look at the images here from my car.

One clue you can look for is to check if the brake pedal becomes hard when the alarm has activated. If it does it means you have lost hydraulic pressure in the braking system and you will have virtually no braking and you should not drive the car AT ALL until the problem is fixed. If you retain normal braking after the alarm has activated the problem is NOT related to hydraulic pressure and you can safely (albeit carefully) continue to use the car. You WILL have lost the ABS function as well as the traction control - which why I advise CAREFUL.

I wish you well in identifying the cause - I know it drove me mad until I finally got it sorted.

Regards


Dave

DavidI

After checking the brake fluid, Adrian's book on the 964 http://www.amazon.co.uk/exec/obidos/...817594-1649237 mentions that if the PDAS light (top right in the oil gauge) and the ABS light (top left of the bottom 4 lights in the same gauge) AND the warning gong are all going then there is a problem with the PDAS control unit - check power to the unit, solenoid, and water in the unit. I'd start by checking the PDAS unit is nice and dry in the front right (when standing in front of the car) of the luggage compartment.

Adrian's book is a highly recommended purchase and you can also get hold of original 964 drive's manuals from Porsche and various specialists - assuming your Japanese isn't up to scratch

amorgan

Thanks for the responses. I have been meaning to get that book for a while. Will definately order it in the morning.
Dave, this happenns prob after about 400 yards of driving and the braking is not affected what so ever.
So as long as pressure remains i take it that it is not a serious problem more of a hair pulling out investigation process.

Computamedic

I'm guessing here, but if the lights go out when the engine is started it's suggesting that the hydraulic pressure is OK (the lights will stay on until the pressure limit switch is activated).

If the lights stay off while standing still try a small test with the brakes. Turn off the engine, turn ignition back on but do not start the engine. Listen for the pressure pump (it should be an audible buzz) and wait until it stops buzzing. Press the brake pedal a few times slowly counting the presses as you go. Make a note of how many presses before you hear the buzzing again. If you get to 5 before you hear the buzzing I'd guess your hydraulics are OK. If you hear buzzing much before 5 the pressure may be low.

If the lights come on as soon as 400 yards I'd be suspicious of the accelerometers. There are two mounted inside the transmission tunnel just ahead of the gear lever, one for longitude (fore/aft) and one for latitude (side/side). If either is stuck it will give the ABS/PDAS system false information and trigger the alarm.

Although it seems not the case with you, if the lights DON'T go off at all it's likely to be a blown fuse for the ABS system. But that may not be the end of the story.

Adrian's book is an absolute must have. He goes into great detail on debugging problems such as this - highly recommended!!!

Regards


Dave

amorgan

Afternoon.
Spoke to a local specialist (La Rose). has anybody here had dealings with these guys before.
Again because of my lack of japanese, could you inform me of the correct tyre pressures for the car. It runs on 17 inch cup 2 wheels.
Many thanks

Computamedic

Try 36psi as a starting point.

amorgan

thanks for all your help guys. took the car to jz machtech last week. two hours labour later and a cleaned out longnitudal (?) sensor all fixed for 95pounds. problem solved. quite a relief that was all.

R6XTERRA

that was all that was wrong with my car as well.....both the longitudinal and latitudinal vavles went on mine....I was told that it could be changed any time. Scheduling for spring time. They have a small, small, small leak under pressure.

Glad you figured it out.

EK

I am having a similar problem with my ABS light. Unfortunately, two different garages have not been able to determine the problem. My ABS light (and not the PDAS light) come on 5-10 miles after I drive the car. The wheel sensors apparently are OK. How did jz machtech determine it was the accelerometers? Thanks.

Pesty

Hi, I was just looking around e-bay and found this.

I remembered this thread. may be of use to you.
http://cgi.ebay.co.uk/ws/eBayISAPI.d...513743188&rd=1