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On the far edge of normal Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 7 Nov 2000 08:38:21
In Reply to: Weird brakes? Another Saab quirk?, Robby 88 9000T, Sat, 4 Nov 2000 19:50:07 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Aero guy has it right. On the 9000 in your year, brake boost is provided by the ABS pump. When the car has been turned off for a while, pressurized fluid drains out of the accumulator (the black sphere) and into the reservoir (where you fill). So the level on the reservoir goes UP. When you start the car, the ABS pump starts to run - it pull fluid from the reservoir (the level drops), pressurizing the accumulator. That's why you check fluid level when the engine has been running - the line reads 'full with charged accumulator.' So if the car has been running, the level should read between the min and max lines.
As you use the brakes, you use the pressure in the accumulator to provide boost. The ABS pump runs periodically to repressurize the accumulator. The level will creep up in the reservoir, then drop back down when the pump runs.
When you first start the car, it takes a while for the ABS pump to pressurize the system. When the ABS and BRAKE FLUID lights go off, the system has pressurized to the minimum acceptable level. The pump will continue to run for a little while longer than that. On a brand new car, the lights will go off after 5 or 10 seconds. As the ABS pump gets old, it takes longer to pressurize (don't we all?) - 30 seconds is not uncommon to get the lights out, and another 15-20 seconds to completely pressurize the system (the quiet buzz behind the dashboard stops).
A few things to do:
First, don't keep your foot on the brake. Not only are you pressurizing the accumulator, but you're pressurizing the whole system. It will take longer. Put your foot on the brake to start the car (a safety thing), then take it off. If the car is going to roll, fix the emergency brake.
Another reason to keep your foot off the brake is that brake lights take a lot of power. Really. It will bring the alternator voltage down a little, and the lower the voltage, the slower the ABS pump runs, and the longer it takes to pressurize. Not a lot, but every bit helps.
I NEVER drive the car off until the ABS and BRAKE FLUID lights go out. Until they go out, you can't be sure you have brake boost. Yes, it takes a while. But if some day the ABS pump decides not to run (like the fuse blows), you won't have boost, and your first stop will be pretty exciting.
If it truly is taking a full 120 seconds to pressurize the system, then the ABS pump is running very slowly. It could be the sign of a very worn pump. The unfortunate part is that replacing the ABS pump is a very expensive proposition, because the parts are on the order of $1200 or so. Yikes! But before you spend the big $$$, try some simple stuff-
The grounds for the ABS system are in the aquarium area (the aquarium is behind the false firewall, where the heater core is), and on the fender. Pull off and clean all the ground points. Make sure the contacts on the connectors to the ABS pump and switches are clean - pull them off and clean them with contact cleaner. If you're not comfortable doing this, a decent mechanic should be able to handle the job. A bad ground will cause a good pump to run slowly. It may be a bad pump, but a hour with some contact cleaner and a wrench is a lot cheaper than a new ABS pump.
Good luck!
, Tue, 7 Nov 2000 08:38:21 <-- Viewing This Message
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