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Re: NO BRAKES!! no pedal pressure, no abs pumping noise Posted by Gene N [Email] (#1094) [Profile/Gallery] (more from Gene N) on Fri, 9 Feb 2007 09:19:48 In Reply to: NO BRAKES!! no pedal pressure, no abs pumping noise, Matt in Sydney, Thu, 8 Feb 2007 02:41:52 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The fact that your pump is not running means that, either it is not getting energized, or the pump has failed. There are relatively few elements in the pump circuit, and you should try tracing the circuit to isolate the problem. The pump is operated by the pressure switch. When the pressure is low, it activates a relay that runs the pump. When the pressure reaches the correct value, the switch opens and the pump turns off. The hydraulic pressure is stored in that sphere (accumulator) to the side of the master cylinder. If the accumulator fails, the pump will run all the time. You have a different problem.
Check to see if there is 12V at the pump. No voltage means you have to trace the circuit back to the battery, which includes the relay, the pressure switch, and the fuse. If there is voltage at the pump, there are only a few things left. The pump has an internal overheat switch that opens if the pump gets too hot. If that fails, the motor will not run. The pump motor could also have an open winding.
If it is the motor or the overheat switch, look for a used ABS master cylinder. I do not believe that either component is available as a repair part. The Mark II system that you have was used on all 1990 to 1992 models, and possibly on the 1993 (hard to tell what was imported to Australia vs. the US). The 1988 and 1989 ABS systems were slightly different, but some parts are interchangeable, like the accumulator. I don't know if you can swap the pumps. You can't swap the whole unit with the earlier system, to my knowledge.
posted by 155.104.3...
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