Been ABS season in France for the last few days. First one was the car belonging to my mate in the South who noticed that the ABS pump was cutting in every time he touched the brake pedal. Assuming, as most of us would, the accumulator on it's way to meet it's maker, he ordered one from Island and fitted it. No difference. maybe air in the power circuit, so flushed through the entire system and bled the brakes. Braking improved no end but the pump was still cutting in every time the brakes were applied. In fact, if he left the car with the ignition on, the pump would cut in for a few seconds every 30 seconds or so without the pedal being touched. Then noticed that when the car was left, the fluid level would rise in the reservoir and drop back down as soon as the pump cut in. So the pressure was somehow dropping and the fluid stored in the accumulator was flowing back into the reservoir. Assumed that there must be a leaking non-return valve in the pump that was allowing the fluid to flow back but before ordering a replacement pump, did a test. Disconnected the hose from the reservoir to the pump and put a length of hose with a funnel on the end on the pump. Poured fluid in, turned on ignition, pump ran and the level dropped. Touched the brake pedal and the level dropped a bit more, the pump cut in but the level didn't rise after leaving it, instead it started filling the reservoir. So the modulator had an internal leak, presumably between the power circuit and the hydrostatic circuit. He ordered a replacement modulator block and took the old one off. This is what he found after he had removed the reservoir.....
Best demonstration of why you should change your brake fluid regularly. I know it absorbs water but wouldn't have thought it would absorb enough to make the internals go rusty. He's now fitted a replacement modulator and the brakes are better than they have ever been since he has owned the car.
The second one nearly caused me grief. Went over to sort out a problem or two on mymisteri's car. I'd already replaced the door latch with one with working microswitches, replaced the drivers window regulator with one with a full set of teeth, replaced the leaking heater O rings and reconnected the heater hoses. Only then did I take it out for a test drive to find ABS and Traction faults and the most evil sounding rear wheel bearing I've ever heard. So, went back yesterday armed with a rear hub assembly complete with driveshaft and ABS sensor. Fitted that, along with a pair of tailgate struts so it didn't drop onto your head when opened and a working remote receiver to replace the dead one so the keyfobs worked. Then took it out for a test and found no noise from the wheel bearing but still had ABS and Tractions faults. Plugged in the Nano and, after a couple of attempts, managed to get it to connect to the Wabco D ECU (1999 car so has the 4 wheel traction control). On my previous visit I couldn't get it to connect but had assumed that the dodgy wheel bearing would almost certainly have damaged or at least moved the ABS sensor. I found that the Nano would only connect with the ignition in position 2 but with the engine not running. Once connected I could start the engine and it stayed connected but there was no way it would connect if the engine was already running. There were no stored faults, the sensor voltages were the same, driving it slowly and the speed displayed on each wheel sensor matched, so all seemed fine. Except that it still had ABS fault on the dash and the ABS warning lamp didn't go out as it should. Tried checking the speed sensors again and noticed that although they were all showing the same speed at 5kph, the right front sensor seemed slower to react than the others. Gave it a tap, saw it move, tried it again and everything was fine. Job done but what I don't understand is why there weren't any stored faults. If I hadn't been driving across an empty car park, I would never have noticed that the one sensor was reacting slower than the others and the problem would still have been a mystery.