[chrisf-1]

Hi again everyone things are moving in the right direction now the rear washer is fixed the power loss is improving but I still have an ABS problem when I first start the car the light is off and the pump is working (I can feel the vibration on my foot and can hear the pump working) within 2-3 miles sometimes longer the abs and traction light come on and the pump ceases working no noise or vibration I have been told abs sensor failure shows on the diagnostics but with these symptoms it is probably a false reading and the pump itself is faulty. I believe recon pumps are available I would like to know what I can expect to pay for supply and fit and also have I been advised correctly. Many thanks Chris

 

[Ronnie]

When you are braking normally if you can feel the brake pedal vibrating and the pump is making a noise then it's indicating a problem, it sounds like it thinks a wheel is locked up when it isn't.

Especially if the light comes on only when being driven. Get the codes read and note the codes, then clear them and drive the car till the light comes on, read codes and if same fault comes up you will need to investigate it, most likely due to a wheel speed sensor needing replacement.

 

[mrbarry]

Commonly its just dirt on the face of the sensor, they are magnetic and rust sticks to them over time fooling the ecu into thinking the wheel is locked. A simple clean normaly works but most garages will replace them anyway so they can charge you. Very old trick!

Here is a quote I made in another thread on here:

The sensors are basically read switches that pick up a load of ferrite sections in a rubber band fixed to the hub, any iron filings sticking to the magnetic parts will tell the abs ecu the wheel is stationary and it will assume it has locked. This makes it try to unlock it by applying the abs system. Also as it thinks the difference in wheel speed front to rear (front undriven and thus reference) is too great it assumes the rear wheels are spinning, at this point the traction control cuts power to try to stop it. After a bit it realises its not working and goes into fault mode.

First step get the fault codes read. This will tell you the wheel to start looking at. In my case the front drivers side, on strip down the bearing was a bit tight and very rough so I also replaced the front wheel bearings

.

 

[steve23002]

Ill third these guys :thumbsup
When the light is on it stops the ABS system from working because it thinks there is a fault. The pump wont work until the fault is sorted. Like the others say, most likely a wheel sensor. :cool

 

[xXNealXx]

Or it could also be the ABS module...codes will confirm.

 

[mrbarry]

Yep, first step read codes. :thumbsup

 

[chrisf-1]

Hi everyone and thanks for your very informative replies. Is this a diy job if so easy or ??? and are these sensors on every wheel and are they expensive many thanks Chris

 

[Gazza600]

Yes mate there are sensors on every wheel.
The fronts are different to the rears though. I got a replacement rear and it cost me £72.00 from BMW.
I also purchased a replacement front from Euro car parts for £28.00.

It's an easy enough job as they are held in my just an M6 cap head screw although the heads sheared off on both mine when I undid them. Even after soaking in WD40 and trying to remove them gently.

The rear sensor was well and truly stuck in the hub and just proceeded to fall apart whan I tried to pull it out. The plastic had perished and just crumbled!
An hour or so of gentle persuasion and a little bit of careful digging and prising got it out:thumbsup

 

[Gazza600]

A more detailed procedure found in another thread mate...


With the wheel off at the corner with the broken sensor, and the sensor cable disconnected, unsnap the sensor wire from the two mount points on the steering knuckle. Follow the cable to the point where it ends at the sensor. The sensor is attached to the car with one or two small bolts. A 5mm Allen wrench is required to remove the bolts. You might have to do this blind, but it's not that hard. After the bolts are removed, gently pull the sensor straight out of its hole. Put the new sensor where the old one was, and reverse the removal process. There were two bolts holding my old front sensor, but the new front sensor included only one mounting hole. Due to the sensor construction, I don't believe it is a problem to use only one bolt. Be sure to hook the new sensor back to the other connector, and don't forget to snap the cable into the cable brackets.

 

[mrbarry]

There are indeed 2 holes in original sensors, only the lower one on mine had a bolt in. The bolt snapped off as expected, steel bolt, zinc coating, alloy steering knuckle, do they want any more random metals to cause electrolysis? :roll

I simply ran a tap thru the top thread to clean it out and re fitted using that one!