HELP needed, Impreza 2004 brake pedal pulsing/grinding
 

Hi everyone,

I have a 2004 Impreza WRX Wagon.

When applying pressure to the foot brake pedal there is a pulsing/grinding sound and feeling, the harder the pedal is pressed the louder and worse it gets.

Usual things to check first would be the discs(rotors) & pads, however, car has just had new driveshafts; suspension struts; anti-roll bushes; discs & pads. Several months ago had lower ball joints; drop links & tie rod ends. No scoring on discs/pads when removed

Only things now not replaced on front end is the control arm bushes, but, before and after these parts fitted the problem exists. Could it be something to do with ABS system? Just seems strange when it's applying pressure to the pedal like it's to do with the calliper, but as I say, new parts fitted.

Any help or advise greatly appreciated.

Just to clarify same issue before parts fitted as now , so new pads and discs can be noisy when fitted till they bed in , but it sounds like the abs pump is working when it does not need to , check the abs sensors are all working ok and properly plugged in , if a sensor is playing up could think there is an issue with that particular wheel , so therefore activating the abs ,hopefully not an abs sensor ring issue , try a code reader to find if there are any codes , next option a full brake bleed 👍

Thanks VXR, to clarify, yes same issue before and after new parts.
It started several months ago after jacking up the rear of the car to fix rear shoes, I first suspected it was the discs/pads on the front as that's what it sounded and felt like so just to diagnose I changed OSF disc and pads for ones off another scooby I have as OSF disc and pads were scored. Problem still there.

Knowing that the CV joints were failing on the front I decided to get all the parts mentioned previously thinking that if the brakes and joints are replaced with new it must surely fix the problem.
Took the car for test drive and problem still there. I think my next option is to take abs sensors off my other scooby to diagnose before buying new sensors

As for ABS sensor ring, that would have been replaced with new driveshaft wouldn't it?

Have you an ABS light when you turn the ignition on if yes and it goes out there is nothing wrong with the electrical part of the system.
When you start travelling if the ABS light illuminates you have a mechanical fault.
The ABS system does a system check when the ignition is cycled and then monitors it all the time once in motion.
Could be a wheel bearing knackered.

The dash lights would have been an important part to include in my original post, sorry.
ABS & Parking lights and have constantly illuminated while driving. I did consider wheel bearing but would have thought there would have been some warning of it failing, this just seemed to come from nowhere after jacking up the car

Turn ignition on and see do they go out. Do not move the car firstly. Then start the car and see do they stay off. If yes travel a little and see do they come on. Have you checked your brake fluid levels.

I'll give it a try and come back to you on that one. Yes levels checked when new brakes fitted and on max

Engine turned on ABS light goes out, Car started ABS light goes out, Car driven and after about 10 minutes ABS light comes on.
Is it worth me checking ABS sensors first?

Now your getting into diagnostic live data by the looks of things. You can watch the wheel speed in graph format and see which one drops out. It could be a dirty sensor or tone ring, loose connection or possible a wheel bearing. Or hopefully not a dodgy ABS pump.

best guess would be the tone ring being damaged when the rear shoes have been replaced / rear disc off ??

I never even gave the rear a second thought as it felt and sounded like a front end issue. And having most things replaced on the front end it would make more sense.
Kwik-Fit screwed up on some work for MOT saying rear disc was seized, had the car 4 days and didn't do any work. I had the car back and had to use hub puller to get disc off which admittedly it came off easy, there was no indication to me that it went wrong but it was after this work that the problem started

Would this feel worse the harder the pedal is pressed though?

Agreed :lol1:

Sounds more like it :thumb:

Is it worth trying to check the sensors are all ok first , not only plugged in properly but working , i say that as is the abs ring a bit of a pig to replace if that is the issue , i still think a code read to find the faulty one is worth doing , could save you a lot of time as you know which wheel is the one with the issue 👍

I'll run a fault check and see if it comes up with anything, might be a stupid question but even if ABS light is on I assume the vehicle would need to be moving for the fault to show?
Also I'll check sensors as I can do a visual inspection of rings at the same time starting with the rear one in question.

Thank you all for the help and advise so far, I will keep you posted

When you start it and the lights comes on as normal then goes off , that’s just saying things are working , when you start moving it’s not properly detecting one wheel , once the light comes up after you have been moving then that’s the best time to check it ,my abs fault was coming on in a few meters , diagnosing / reading the fault light , it all depends on the code reader , subaru use a different system to other cars , some readers i have only look at engine codes , it may read a code if it’s still on , but unlikely if it’s been turned off and not showing , but I bought one on ebay for 100£ or so which looks at more including abs and srs faults , find a friendly garage , it is solve able , helps to know which wheel to look at , hudt to save you time , hopefully just a sensor as it’s an easier swap 👍

Post 4 explains the operation of the ABS system.

👍😁 as above