RAPID 95 993/4

I drive a 95' 993 awd, every time I start the engine, the brake warning light goes on, and stays'on' for around 30sec, and at the same time I hear a humming noise comming from the left hand side at the front of the car. Porsche mech. told me it was the brake fluid pump pressurizing the circuit..?
It seems to take a long time, is it normal, anyone can comment?
Thanks.

Larry T.

I have a 95 993 c4 as well, and my car does the exact same thing. My understanding is that this is completely normal, and only happens on the C4. If you look in your owner's manual, you should find a supplement insert that explains this.

If you can't find it, I'd be happy to email you a copy.

DJ

My car does this too, and has done it every day for the last 50,000 miles. I think that the warning light stays on until there's sufficient pressure built up in the brake booster (?) system.

Jack

My car does it also--it's normal.

H. Miller

I had a 95 C4 coupe also and had similar experience. When I asked the service manager at the local Porsche dealer he said it is normatl AT initial start and for first 30 seconds as you describe. BUT, if the pump comes on during normal driving (and it is a noticeable hum), it may be going bad. Mine was coming on during normal driving. I ended up selling the car before having to replace it (that wasn't the reason I sold it).

RAPID 95 993/4

Thanks ,I feel better about it now!

Ran

98C4S,
I'm not sure about that piece of info that your dealer told you though it may just be my car - someone who has a second opinion please go ahead... The brake pump hum or whatever we want to call that sound seems to go off once in a while in my car even after initial start though of course I could be mistaken and it may be some fan going off etc. But I'm fairly certain that my pump goes off perhaps at a stoplight etc. And I do not think that my pump is defective or atleast my brake system was checked twice due to a brake bleed foul up recently. OH, I dont think it comes on WHILE DRIVING but would I hear it...

THUS, I have only heard it at stoplights or just before backing into garage and of course at initial startup.

[ 07-06-2001: Message edited by: Ran ]

Jack

Ran:

Your car is fine. If you had a problem, the brake booster light would come on while you were driving. Everything you described sounds normal to me.

Anir

My 993TT does this as well - only at initial start-up. Interestingly, I bought the car with 6,000 miles, and it never happened until the car had about 8,000 miles. Also, on some days, it doesn't happen at all.

Adrian

The ABS pump will crank up every time you start the engine to pressurise the system. It is purely controlled by the pressure switch. Once the system is pressurised, which means once the accumulator is charged up the lights will go off. The brake accumulator holds the max pressure for about three of four brake applications.
It is very normal, in fact highly desirable that the ABS Pump works whilst you are driving. It takes 25 pumps of the brake pedal to completely dump the pressure. Each person can easily check that the pump works. After all thelights are off, pump the brake pedal three of four times hard, the pressure warn should come on the warn buzzer sound and then very quickly goes off. How fast it goes off after this test, actually checks how sealed the system is and how good the pump is. Faster is better.
This ABS Pump should be intermittantly be turning on and off and running for only a few seconds at a time after heavy braking efforts. No warn lights should come on of course. If they do something is wrong.
Ciao,
Adrian
911C4
944

Chris Cantrell

Hi,

I am new to the site and also Porsche I just purchased a 95 993 and have a question in regards to a brake sound, which seems similar to what is discussed here. When I start the car, I get a humming sound (like a small pump or something) which lasts about 30 secs. It also happens whenever I put on my brakes, like at a light - all the time. I don't get a light on the dash though.

Does anyone have a suggestion on it might be?
Est cost to fix / Part Numbers?
Something that needs to be fixed ASAP?
Can it be a DIY project?

I had the hydrolic fuild replaced and that did not correct the problem. The local used dealer (was not a Porsche dealer) thought it would.

Thanks in advance for your help!

-chris

jacksonking

Chris -- Mine has always done the same thing. What you describe is normal. Don't worry about it.

Jack

vjd3

I'll second that; the pump on my C4 will run for 30 seconds or so on first start, and come on for 5-10 seconds every third application of the brakes. My mechanic said that's perfectly fine.

Vic
95 C4

Chris Cantrell

Thanks for the reply's. This is good news, at least from my wife's check book perspective

It is anoying to say the least. Has anyone tried to "muffle" the sound?

One other thing I have noticed is my brakes are very hard. There is not much what I will call play or being able to push down to the floor. Is that normal or maybe something related to something else?

Thanks again!
-chris

vjd3

It's an AWD thing ... just the Turbo and the C4. It's pretty loud, but you get used to it. It sounds a lot like an ABS pump. but it's actually louder.

Vic
95 C4