993 C4 brake booster pump issues?

[prrussd]

I just purchased a '96 993 C4 coupe and have a feeling there's an issue with the brake system. Upon startup, after the car has been sitting 8-12 hours, the brake booster pump runs for about 30 seconds with warning light on and a little longer after the light has gone out. The pump also cycles -- what I'd consider often -- breifly (5 secs?) during regular driving. At a stand still depressing the brake pedal twice with moderate pressure, or four times with light pressure, causes the pump to cycle briefly, though the light does not come on. Car has 64,500 miles and has been well maintained. I dont remember seeing previous brake issues in the maintenance history. Is this normal or is there a leak somewhere? I'm not familiar with the whole setup. Thanks.

[Flieger]

Sounds like there is a bad pressure accumulator somewhere but that is all I can suggest, not having experience with 964s. Welcome to Pelican, though.

Do you have the ECU computer error code reader commonly called the "hammer"?

[lucittm]

My warning light comes on after I start the car in the morning. It goes out after 10-15 seconds. It never comes on again until the next morning.

Mark

[911Urge]

Bleed the entire system if you feel comfortable doing that. There are DIY's all over the place to help you do this. Then monitor the system and see if that changes anything.

[cgfen]

Originally Posted by prrussd

I just purchased a '96 993 C4 coupe and have a feeling there's an issue with the brake system. Upon startup, after the car has been sitting 8-12 hours, the brake booster pump runs for about 30 seconds with warning light on and a little longer after the light has gone out. The pump also cycles -- what I'd consider often -- breifly (5 secs?) during regular driving. At a stand still depressing the brake pedal twice with moderate pressure, or four times with light pressure, causes the pump to cycle briefly, though the light does not come on. Car has 64,500 miles and has been well maintained. I dont remember seeing previous brake issues in the maintenance history. Is this normal or is there a leak somewhere? I'm not familiar with the whole setup. Thanks.

this sounds like typical behavior for a 4S.
My car does the same thing ,but initial start up cycle time is closer to 20 seconds.
the pump is designed to run during drive cycle as you use the brakes and deplete the accumulator pressure.

[prrussd]

Great - thanks everyone - I'll let it go for now and see if it gets worse.

[sml]

964 C4 ... same

[adeak1]

Same problem-three year and no problem and with no change

It looks the nature of c4

Andrew

[cgfen]

Originally Posted by prrussd

Great - thanks everyone - I'll let it go for now and see if it gets worse.

what you describe is NOT a problem.
It is a engineered behavior.
sleep well.

Craig