Strange ABS Fault

[JimF]

Got a strange ABS fault. Car is a phase 2 172, standard brakes and recent ATE fluid. Never been able to engage ABS, also the ABS light intermittently comes on, and when it does, the braking power is significantly less. Only recently noticed this connection. Presumed I'd just cooked the fluid at Oulton, but the other day the ABS light went off and the brakes returned. Then the next day they were bad again. Any clues? Bad fluid? Air in the ABS system? All of the above? I noticed the other day the ABS rings at the front have seen better days. Also, I don't have the 'Stop' light on or any other lights, and I don't particularly want to get rid of the ABS

 

[JamesBryan]

Air or knackered pump at a guess.

@bloke?

 

[JB21]

Sounds like your brakes are going into fault intermittently, so going from 50/50 bias (weak braking) to normal 90/10 bias or whatever it is (normal braking). This will be electrical, and sounds like a connector issue. Try the connector that sits in the passenger A-Frame first then follow that to the ABS pump, then all the way to each individual ABS sensor if you cant find a fault at the a-frame or pump.

 

[bloke]

Could be few things but the connector is always worth checking. How bad are the reluctor rings?

 

[JimF]

Cheers guys! The teeth on the driver side ring are pretty rounded off. Would a photo help diagnosis?
Will check all the connectors.

 

[JB21]

Cheers guys! The teeth on the driver side ring are pretty rounded off. Would a photo help diagnosis?
Will check all the connectors.

Could be the rings but IME it didn't give out an ABS fault, it just tried to murder me instead as the side with the cracked/worn ring slipped under hard braking causing the wheel to lock up, whist the other wheel engaged the ABS causing the car to swerve to one side.

Get a pic anyway.

 

[JimF]

Will jump under at the weekend and take some snaps. I've managed to lock the wheels, get brake fade from track use, and tried extremely hard.... But never have I been able to engage the ABS. Warning light on or off.

 

[JB21]

Will jump under at the weekend and take some snaps. I've managed to lock the wheels, get brake fade from track use, and tried extremely hard.... But never have I been able to engage the ABS. Warning light on or off.

I struggle to get the abs the kick in, think it's just the system as I've tried with RC8s on cold road tyres it just used to lock the nearside front. Gonna do a caliper rebuild to see if that helps.

 

[JimF]

Ok that's promising, thanks.

 

[JimF]

Try the connector that sits in the passenger A-Frame first then follow that to the ABS pump...

Excuse my ignorance, what do you mean by passenger A-Frame?

 

[JB21]

Excuse my ignorance, what do you mean by passenger A-Frame?

Have a look under the car passenger side and you'll see towards the front of the car an A shaped piece of metal and underneath that will be a connector for the ABS wiring. The A-frame is roughly around where you'd jack the car up at the front.

 

[bloke]

Brace piece that goes from the back of the front subframe to the floor of the car. 4 13mm bolts holding it on.

 

[JimF]

Perfect thank you!

 

[JimF]

Managed to get under be car yesterday. Removed the A brace and the connectors all seems fine. No wire issues I could see and it's not like there's any movement there. Nothing obvious around the ABS components in the engine bay either. Will check the ABS rings tonight. How hard are they to change at home?

 

[DomP182]

Anything from dead easy to a pita if like me you can't get the drive shaft to knock through the hub, stuck solid!

Sent from my SM-G903F using Tapatalk

 

[JimF]

That's what I thought!

 

[JimF]

Right! Looking to change the ABS rings this week. I've got a handy mate to help. Anything else worth changing while it's in bits?

 

[JB21]

Right! Looking to change the ABS rings this week. I've got a handy mate to help. Anything else worth changing while it's in bits?

Camber bolts?

 

[JimF]

Good call, but did those last month

 

[JamesBryan]

Lower ball joints?

 

[JimF]

Think it's had those recently actually. At least one lol

 

[JimF]

(Updating this to help other members in the future)
I’ve fitted new ABS rings to the front and bled the brakes. I can engage ABS now. However it seems to alternate between working correctly, locking the rear wheels, and engaging ABS and pulling to the passenger side. Making progress at least!
I’ve also got an inconsistent pedal I’m trying to fix, but before I replace the master cylinder, would changing the front ABS sensors fix the ABS problem? Or at least the drivers side sensor? Or would it be the case that if it needed sensors would the ABS and speedo not work and there be warning lights?
Thanks in advance.