Scrooge

Typically, after I leave the car ('90 C-4) overnight and start it the morning, the brake pressure warning lights come on and I can hear the pressurizing motor running for about 15-25 seconds. My dealer has told me that this is normal operation. I have heard that this may also be attributed to a discharging battery. The car has sat for up to three weeks at a time with no starting problems so I am doubting the battery issue. Yesterday, I took the car on a short trip and it sat for only two hours before being restarted and having the warning lights come on (accompanied by the hydraulic motor running) for 20 seconds or so. Any ideas about what may be going on here? Could Phoenix daytime heat have anything to do with it?

Thank you in advance for your help . . .

SonnyV

See what I wrote below for the same problem as your car is having.

>>>>>>>>>>>>
Thanks to everyone who helped me with the original problem.
and to those who are interested, my car, a '92 C2 Turbo with
38.2k miles, developed a problem with
retaining hydraulic brake pressure after the car is parked
for while (overnight or even 1/2 hour)

Recap: At first, the pressure would build up within second
upon startup. Later on
the pressure is gone and took a long time to build up. The
symptom is the brake
warning light on and with beeping sound. This could last up
to 15 minutes after
starting the car. During this time, the brake effort is
rock hard and no brake assist.

The problem was traced to the brake servo hydraulic pump at
the front trunk, driver side - forward of the brak reservor
(sp?). It tooks hours of testing to find out the exact
problem. The replacement part alone is ~$670, and it
requires a couple of hours of labor - including plushing the
brake system and replace with new brake fluid.

There was someone on this board with the same problem. All I
could said here is that you have to test the brake system
and isolate the problem one part at a time. Your problem
might not be the same as mine. Don't replace the same part
that I did.

I did not expect it to cost so much, but that is the price
to drive one of these cars. Too bad I don't drive it as
much as I want to because of back pain. This is the first
major thing I have to do on this car since I bought it last
Oct.

I hope to get the car back soon. Yesterday, after I paid the
bill to pick up the car, it did not start. There is/was a
problem with starting the car right after it has been
sitting for 30 mins but less than 4 hours. The idle would be
rough but the car will not stall. Yesterday it did. During
the entire week at the shop the car did not have that
problem until yesterday late afternoon.

Sonny Vo
'92 Zermatt Silver C2 Turbo
<<<<<<<<<<<<<<

Michael W

Hmmm,
I notice the electric motor running too for seconds right after starting. I always thought it was the fuel pump motor priming the fuel injection. In fact, if you just let the car sit there and idle, you will here the electric motor coming on once in a while. When the car is moving or running at higher RPM, the siphoning effect keeps the fuel running without pumps.
As far as the brake warning light (sometimes the 4WD light too) coming on after starting, I think it is just doing its diagnostics.
I could be way off, anyone with better explainations?

Mike

Harold

Guys,

As far as I am aware, it is normal for most 964s to build up their brake pressure after being stationary for a while. Also after driving the car quite hard with lots of heavy braking, the pressure levels tend to reduce requiring the pump to work its magic. What is not normal, is having the pump stay on for excessively long periods of time or coming on for no apparent reason.

There may also be air in the brake system, causing the pump to work over time- if this happens, you could end up with an extremely hot pump with a melted connecting hose that results in a pool of brake fluid in your front comparment. Oh yes, your brakes may fail at this time also...

Actually happened to me- rather scary.

Cheers

HaroldComplete 964

Scrooge

Thank you all for your responses so far. The general consensus seems to be that those of us who have the hydraulic pumps coming on periodically during normal daily driving are witnessing some sort of malfunction. Is this correct? What is the best course of action then as far as diagnosis? As I said, I took the car in to the shop for this once before, but they passed it off as normal operation

Sonny- You mentioned that you are having hot start problems also. Did the shop seem to have any specific ideas as to the cause of this?

Adrian

NO THIS IS NOT CORRECT. The ABS hydraulic pump will activate all the time when the brake pressure drops. Push the pedal a couple of times or three whilst stationary and the light comes on.
As times goes on this will happen more often as the gas charge of the accumulator falls and the pump starts to wear.
It is when you do nothear this pump that you have real problems. On a 964 a really hard pedel means you have no brake pressure in the sealed system whichmeans, NO BRAKES. Pedal to the floor means yoiu have a huge hole in the system and no hydaulic fluid.
Everything scrooge in your original post is 100% totally normal and correct. If all your lights go out within 120 seconds of start (20 seconds for a new 964 and 120 seconds with a well worn out system) all is okay. There are 23 metres of hydraulic pipes to pressurise on the 964 C4. This takes time. The alarm going off is also quite normal especially if you have had the aircon running, been using the windows and had the headlights on. The alarm bleeping MORE THAN THREE TIMES is an indication of a failing battery or a timeout function which indicates the brake ABS pump is behind schedule.
The hot weather does have an effect on the brake fluid as well.
If ALL THE WARN LIGHTS ARE OUT and they do not come on again then everything is okay.
However if you wish to chase non existent faults and pay somebody to do it, I will happily take your money (just kidding),
Ciao,
Adrian
911C4

PS: Scrooge, Sonny has a Turbo. You cannot compare the 964 hot start problems with the C2 Turbo hot start problems. Just push the pedal a couple of times (only when it is hot and not flat to the floor). Porscxhes are not designed for the weather you are using it in. Fuel vapourisation is the most common cause of this. The fuel lines have to run a distance and if everything is hot it vapourises.

Jeff Curtis

Interesting that some of you mentioned the possibility of a discharging battery causing this...as I had experienced this light and "beeping" alarm several times prior to changing out the p.o.s. "plain label" and leaking battery that came w/the car.

I put in a brand new Interstate battery and haven't noticed that the brake light and alarm hasen't come on since! These posts are great, now I realize the battery may have eliminated the sporatic brake alarm.

Thanks guys! I'm going to sleep better now.

horst

scrooge, relax. All is right in your world.