Standard Issue

Hi all I'm having what I think might be a brake bomb or booster fault on my 5000q (100). The car has done approx 140k miles and the steering and brakes work fine. However if I leave the car overnight and turn the ignition on but don't start the engine then after about 60 seconds the bleeping starts and I get the flashing red triangle. I also noticed that the level in the fluid reservoir rises about 3/4 inch. When I then start the car the flashing triangle sign stops and the level in the reservoir drops a little and steering and brakes work fine. There is a little weep of fluid from one of the X bolt heads on the steering pump but only enough to notice. Do I have a problem with the pump or the bomb or maybe the booster?

Kneale Brownson

Run the engine some, then shut it off. Pump the brake pedal until you feel it get hard. If you get fewer than 5-10 pumps, you need the pressure accumulator ("bomb") recharged or replaced.

Standard Issue

Hi yes I checked that out and it seems to have about 30 pumps of the pedal before it goes really firm. After doing that the reservoir level also increases by about an inch. So bomb seems good? Still getting the brake warning light coming on if I have the ignition on after leaving the car for a while.

Kneale Brownson

Sounds like your "bomb" is OK. There are two brake sensors that may be contributing to the red brake warning, the one on the top of the hydraulic fluid reservoir and the one on the brake fluid reservoir. You might want to check their wiring.

Standard Issue

Thanks for the reply I have checked the wiring on those two reservoirs and neither has any affect on the warning light. What does is if I disconnect the pressure warning light wiring at the sensor behind the brake booster. That stops the warning light and the beeping. Could the brake "bomb" be slowly loosing pressure causing the sensor to activate with the engine off even though the brake pressure accumulator works fine when the engine is running?

Kneale Brownson

The brake "warning" light is supposed to show when you turn on the ignition and don't start the engine, I believe. It's been a long time since I had a 5K car.

one5k

the brake light will show if the key is on with engine off after a while. mine always did this

Standard Issue

Thanks Kneale and one5k that is what I was thinking might account for the warning but it doesn't mention it in the owners' handbook. I've done a couple more tests after some searching on this forum and disconnected the return line to the reservoir from the booster. If I push the pedal then fluid pumps from the line and then about 1/2 an egg cups worth continued to come out in drips over about 15 mins. If I then start the engine after doing the 30-50 pumps of the brake pedal to get it firm then the increased level in the reservoir drops very quickly, approx 10 seconds, by about 1 and 1/2". It could be that the warning as you say is supposed to chime with ignition on but I have a feeling that the problem is a slow loss of pressure from the booster or "bomb" that is causing the low pressure sensor to activate? Is there any other test I can do to see what might be causing this or should I replace the booster with another. Can they be repaired? Are they difficult to get hold of new? I'll keep plugging away at this.

Kneale Brownson

I recall a DIY "test" where you disconnected the line from the booster to the reservoir after discharging the "bomb" by pumping the brakes, and if fluid came out, the booster needs replacement. Not clear on the details of this testing procedure (old man, old memory). May be in the archives of the online Audifans email list: http://www.audifans.com/archives.php