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Premium Member
4,807 Posts
Aye it only has to hold up for an hour or so to get your ticket.

I was wondering, I don't know if the ABS unit needs bled via software on these. On vag cars it's a nightmare if you get any air in the ABS unit, you need to get VCDS software and purge the unit.

Just wondering if some air is still sitting in there causing this random behaviour.

I would definitely check for a level sensor too. Should be a plug going into the reservoir which you may be able to get a multimeter on or bridge the connections to diagnose.
the random behaviour is probably due to a faulty or failing pressure sensor which is located inside the pump.
common fault

12 Posts
Discussion Starter #22
Good shout, from the behaviour that does seem highly plausible seeing as the replacement pump was from a scrap yard (might be faulty or might have needed waking up a bit), or perhaps there were air bubbles in the pump from the fluid change that might have worked their way out now and affected the pressure reading? Either way the problem appears to have gone completely now and iv'e just bagged (blagged) my MOT. If the issue comes back (as it probably will) i'll be sure to switch the pump for a tried and tested replacement with he correct type and serial numbers and report any findings back.

For future readers the things (half) learned were
  • Abs and service light on only = possible faulty ABS pump module
  • If changing the ABS pump module ensure the part and serial number match (though in this case it appears i got away with it so possibly some cross compatibility between certain types? though i haven't actually tried to skid yet so don't properly know if the ABS is fully functional)... also put a pan down as the vacuum doesn't hold it in and it will drain the whole tank right on you. ha ha
  • Intermittent Abs, service light, stop and parking break light = possible ABS pump pressure sensor issue or brake fluid level/sensor issue.
  • Best to use a code reader first if you can rather than shoot in the dark as you might go round in circles like i did.
Thanks again all for the input, great forum (iv'e just moved over from a fiat forum as i just switched vehicles this year)

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