ABS problem, pulsates to every stop...

[SB98UKexplorer]

Never ending problems on this beast, well the abs pulsates before i come to a stop and after that the abs light stays on and im back to normal braking (no abs just locks all wheels up), then after you can turn the ignition off and back on to take the ABS light off and have dodgy ABS working.

Iv had the front right hub replaced due to bearing collapsed and still is behaving the same, had the other side abs sensor cleaned and picked out dirt from the ABS ring in the hub and still acting the same, tried checking the rear ABS but its hard to take out, could only twist it?

Iv had the ABS motor replaced to another same year and still acting the same?

Is my only culprit the rear ABS that could couse this?

Also iv pulled the plug on each ABS sensor and the ABS lights up on each so they work?

Iv checked the OBD and theres no fualt codes.

What do i do now?

 

[kernowman]

I know the problems well enough that the ABS can give - see my posts of a couple of weeks ago. I am still waiting for a new sensor to arrive which should cure mine.
My front sensors appeared good and tested correct with the ABS light going out after a couple of seconds, yet I got a pulsating pedal during the final part of braking. I checked them both for open circuit with a meter across them - they gave an identical resistance each, so naturally assumed they were good. However, a few days later, I then jacked up each wheel in turn and spun them by hand, again with a meter across them. The RH sensor gave quite a good pulsating reading, but the LH one only gave a very tiny reading, even though it looked good. Naturally, I then took it out and made sure the ring was clear, which it was. It appears they can go faulty, yet still test good.
My seemingly never ending search through other peoples problems with the ABS rarely came up with problems with the rear one, unless the cable was broken. Have you checked the resistance of the front ones and seen if they have a good output? The above may not cure your problem, but there is a possibility it may help to eliminate a couple of points.
Richard

 

[Velocity4x4]

sounds to me like one of (or both) the front abs sensors and these cant always be detected as the cause unless you change them

 

[Blacksheep Josh]

on my 93, i changed my brake pads out and the ABS woudl pulsae for NO REASON AT ALL. i didn't know what else to do, but because this was my first vehicle with ABS, i was used to driving without it. so i took out the fuses for about a day. i put them back in, and it worked fine.

can't tell you why, but it worked for me.

 

[kernowman]

Nothing more than dodgy ABS to make you a nervous wreck. I am only just sorting mine now, so have been running for the past two months with fuse 14 pulled and no ABS. ABS light on all the time is a bit annoying, but brakes work just normal then - after all, we used to drive many years ago and still do with a lot of cars that had no ABS.
Richard

 

[SB98UKexplorer]

iv just tested the front two, rotating the wheel off the ground, the right hub that was replaced recently from a 70k explorer has a ohm reading from 380 to 425, the left wheel thats all original has a reading from 405 to 420 ohm, im making a cable up to do the rear so i can read it whilst driving as its difficult in this rain to even rotate the rear by hand.

what sort of Ohm reading should i be looking at for these sensors?

 

[kernowman]

I have a new hub and sensor here, but unfortunately do not have a very accurate meter - I am getting a reading of about 1300 ohms across the sensor coil. This should read the same if the wheel is turned or not. When you turn the wheel, if my rather rusty electrical knowledge serves me correct, you should get an AC voltage - I get around 5 volts on the meter turning the hub by hand. Hope somebody more qualified can confirm this, but for now this may be something to be getting on with. I assume the rear one should read the same. I do seem to vaguely remember somebody in a garage sometime back saying the figures of 1500 ohms and 5.5 volts so hopefully I am correct.
Good luck.
Richard

 

[kernowman]

To add to my last post, I should not think the resistance of the coil should make much difference (unless of course it is open circuit). I would have thought the output of the sensor is more important, as well as the outputs of each one being of a similar level.
Richard

 

[SB98UKexplorer]

well iv checked the rear and im getting a reading between 900 to 1300 ohms when rotating the rear wheel about 10mph

 

[SB98UKexplorer]

on my 3rd spare hub im getting a 411 stop and between 380 to 480 rotating, so all 3 front hubs are in the roughly same area, not sure about the rear sensor?

 

[BIGHVM]

Just had a thought have you checked you have the vac pipes to servo on right and they are not leaking?

 

[kernowman]

Are you getting a voltage reading when rotating?

 

[SB98UKexplorer]

they vary between 3-6ish volts on all 3 hubs (1 spare) and 380-420 ohms on all 3, except the rear i only took a reading of ohms, that was between 900-1300.

 

[kernowman]

Not written for an Ex, but most systems seem to be similar, try the following link for more info.
http://www.honestjohn.co.uk/forum/post/index.htm?t=16782
Richard

 

[kernowman]

The resistance of the front hubs seems low compared to the average, but then again it is similar for all three hubs (incl. spare), so logically it can't be wrong. ABS light goes out OK and this only checks resistance, so that seems good. The voltage output, which is probably the most important, also seems OK, comparable with mine. Hopefully, now the holiday is over, somebody else may be able to throw a bit of light on the subject. Does your model have a seperate ABS control module or is it built into the pump which you have already replaced? If seperate, wonder if this could give dodgy symptoms or whether if they go, they die completely!!!! Afraid modules are beyond my scope.
Richard

 

[SB98UKexplorer]

In my next hunt im looking for the RABS test connector, it stores a code when there is a problem with the ABS, i had a nose under the feet area and the connectors by the side wall to find this small lonly connector to retreave it, i just cant find the thing?

 

[kernowman]

Never thought of looking in my Chilton Manual Front resistance should be between 270 and 330 ohms. Rear should be between 800 and 1400 ohms.

 

[kernowman]

Don't know if you have the Chilton Manual, but it says Rabs Connector (91 to 96) is located on the main wire bundle inside of cab under the dash, slightly rearward drivers side. 1997 is located on the forward end of the power distibution box, under the hood. You are looking for a connector with an orange/black wire. I assume you know how to read the codes.
Richard

 

[SB98UKexplorer]

Never thought of looking in my Chilton Manual Front resistance should be between 270 and 330 ohms. Rear should be between 800 and 1400 ohms.

well they seem to be in that area so i could take it as they are allright, till i get a RABS check ill see whats really wrong. thankyou all