ABS not working

[piotr]

Driving this morning I found a bit of road where it was safe to do emergency braking as I wanted to test if the brakes operating as they should.
So I hit the brake pedal and -surprise.Lots of smoke from front tyres.Both wheels locked up.So no ABS at all,but I don't have any warning lights indicating fault in braking system???
Any ide boys?

[piotr]

Just to add-my vacuum pipes to rear diff lock actuator are not connected at the moment but I don't think this would stop ABS from working?

[M2ki]

If you turn ignition on, abs light should turn on. Do you have abs on off button?

[piotr]

hi and thanks
Yes-ABS light coming on and then goes off as normal on self check.
No,i dont have switch as its 95/96 modey

[M2ki]

Thats weird. Abs light should turn on when there i a fault.
Maybe someone has fitted a led with a delay to pass the MOT.

[piotr]

No no,ABS was working perfectly fine before engine rebuild.
I know,it's very strange that it's not working but it's like system don't see it?

[M2ki]

The system is really basic, only 4 wheel speed sensors. If one of the sensors is not working, it should trigger warning light. If you have vcds/vagcom, check for faults and if all 4 sensors are showing speed signal. You can use diagnostic upto 20kmh, after that the abs module disconnects.

On the abs pump, under the black plastic cover are 2 relays, for valves and pump. Check those.

[piotr]

The system is really basic, only 4 wheel speed sensors. If one of the sensors is not working, it should trigger warning light. If you have vcds/vagcom, check for faults and if all 4 sensors are showing speed signal. You can use diagnostic upto 20kmh, after that the abs module disconnects.

On the abs pump, under the black plastic cover are 2 relays, for valves and pump. Check those.

Cheers for that-I have got spare ABS module so will try relays of that one.

[piotr]

I wonder is there any special way of bleeding the abs pump itself or not really?
Mine has been removed from the car for very long time so I just thinking if this might have something to do with my problem?

[shorty_94]

This could be your problem!
As far as I know, you have to bleed your hydraulic block with the help of VCDS or another tester. Bleeding it just through pumping your braking pedal does not work, because you can't get out the air bubbles if the valves don't move.

[Rubberdubber]

If you had air in the ABS you would have a spongy pedal? usually in my experience you find this out when racking your brains as to why you can't get a decent pedal and the only thing left is a Vag-com bleed. I have done them, it a PITA and goes through fluid like there's no tomorrow, so make sure you are well stocked before you start. when you are bleeding the brakes if you use a pressure bleeder and for any reason it runs low or out of fluid it can draw air into the system which usually ends up in the ABS, if you haven't done anything like that then I would doubt tat's the problem. I am sure there are You-Tube videos about Vag-Com bleeding, probably Mk4 Golfs from memory but I am sure the process would be very similar.

[piotr]

Thanks for that boys.Like I said,that ABS module was out of the car just seating on the shelf for about one year.I only done brakes bleed in traditional way so if it needs vag com to open valves in module then I guess this is why it's not working .pedal is not too bad but in the same time ,I wouldn't say the brakes are great.

[Tom_]

I am curious, how bleed brakes (with ABS) when u can not use a VCDS on Coupe Quattro 20v 89 year. How opens ABS system with no diagnostic. I know that is recommend using a US 1116 for a bleeding, but who is got this?

[piotr]

So I did borrow Vag Com from my friend today hoping I will manage to open valves in pump but it's not working-it's coming with error-will have to find some other way to force valve to open.

[Error404]

Perhaps one of the relays on the pump has a fault. Sure you can "hot-wire" the ABS pump to test it. After-all it is only a pump controlled by an ECU. You should be able to activate the solenoids in the ABS unit also. I would image the ECU pulls to earth to activate these. Will try and take a look at the electrical schematics later