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Old 28th September 2014, 22:32   #1
ROVER-25X
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Default ABS kicking in at low speed

Car failed the MOT on many items but the ABS fault is the more important
one, first things first i'll clean up the ABS sensors and check the wiring, i'll
also check the reluctor rings, have no lights on the dash, is that normal for
this kind of fault or should something show up ?

Tried my ELM OBDII but nothing came up.

Car is a 2001 Classic SE derv.

Any other elimination processes I could try ?

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Old 28th September 2014, 23:53   #2
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The 75 doesn't use reluctor rings, the magnetic ring is part of the wheel bearing.
Also, you won't get a sensor out in one piece to clean up - they usually come out in many pieces with a heck of a fight.
ABS crunching at low speeds is either a sensor on the way out, or a worn wheel bearing causing a variable gap between the sensor and magnetic ring.

Welcome, by the way! Not seen you on here before Charlzy.
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Old 29th September 2014, 06:46   #3
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Default Reluctor ring

I had this with my old 2003 zr td, turned out to be a split reluctor ring on one of the wheel cv joints, I did get some spare ones off ebay for only a few quid but then had no idea how to get the old one off as there was so much rust, the answer I found was to buy a new cv joint, only cost me about £35 and the problem was sorted straight away.

Issue was with the time increase in gap where the split was the car thinks that the wheel has locked up and applies the abs, then it sees the wheel is moving and releases and the cycle continues giving the low speed dum dum dum dum effect.

Hope that helps.

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Old 29th September 2014, 06:56   #4
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Different set up on the ZR. Best way to check the sensors and magnetic reluctor rings if you don't have access to T4 or other diagnostics is to use a voltmeter.

Jack the wheel up, connect the meter and rotate the wheel slowly. The voltage should change from 0.7v to 1.7v as each segment passes the sensor.

Interestingly on my car the aftermarket rear sensor wasn't quite near enough to the bearing, and randomly missed segments but only at very slow speeds. Filed a couple of mm off the sensor bracket and all was well.
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Old 29th September 2014, 07:17   #5
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A T4 session should identify where the problem is.

Without seeing it, i will guess at nearside rear sensor dirty.
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Old 29th September 2014, 13:44   #6
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Default ABS kicking in at low speed

Quote:
Originally Posted by rich17865 View Post
A T4 session should identify where the problem is.

Without seeing it, i will guess at nearside rear sensor dirty.

That's what mine was. Rust had got between the brake back plate and hub causing the ABS to kick in whilst braking at low speed. It did involve a new rear wheel bearing but the ABS sensor was fine and all 4 sensors were checked out at the same time, rather surprisingly all 4 sensors came out in one piece.

As Rich says a T4 session will help isolate the fault, why not attend our NW meet on the evening of the 7th or daytime on the 19th when Rich and T4 will be in attendance?
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Old 29th September 2014, 14:25   #7
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Charlzy, come down to the meet at the Hollow Tree - http://www.the75andztclub.co.uk/foru...splay.php?f=83

rich17865 has a T4 he brings to every meet. Much cheaper than mucking about with the sensors and bearings.
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Old 2nd October 2014, 19:51   #8
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Quote:
Originally Posted by DMGRS View Post
Also, you won't get a sensor out in one piece to clean up - they usually come out in many pieces with a heck of a fight.
ABS crunching at low speeds is either a sensor on the way out, or a worn wheel bearing causing a variable gap between the sensor and magnetic ring.

Welcome, by the way! Not seen you on here before Charlzy.

Thats because I could smell you were here and I didn't want any debris
thrown at my car.




Quote:
Originally Posted by Mike Noc View Post
if you don't have access to T4 or other diagnostics is to use a voltmeter.

Jack the wheel up, connect the meter and rotate the wheel slowly. The voltage should change from 0.7v to 1.7v as each segment passes the sensor.

Nice one Mike, i'm getting it up on axel stands as soon as so I can get the tires replaced, my Mechanic mate said he would give us a touch with a volt meter, he's ex-BMW too so is familiar with the set up.




Quote:
Originally Posted by rich17865 View Post
A T4 session should identify where the problem is.

Without seeing it, i will guess at nearside rear sensor dirty.

Yeah cool mate, as per our chat will defo sort something out.




Quote:
Originally Posted by vindaloo View Post
That's what mine was. Rust had got between the brake back plate and hub causing the ABS to kick in whilst braking at low speed. It did involve a new rear wheel bearing but the ABS sensor was fine and all 4 sensors were checked out at the same time, rather surprisingly all 4 sensors came out in one piece.

As Rich says a T4 session will help isolate the fault, why not attend our NW meet on the evening of the 7th or daytime on the 19th when Rich and T4 will be in attendance?

Cool will bare that repair in mind.

The car is not road worthy folks so any offers of T4 sessions and meets
are on hold for now but many thanks for all the help, will crack and and
see whats, well, the craic.
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Old 2nd October 2014, 20:02   #9
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By the way, should I have a warning light/message on the dash
for this as I don't have one ?
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Old 2nd October 2014, 20:11   #10
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Yes, I would expect an abs light, I suspect dodgy interference to get it through an mot in that case.

Does the abs light come on when you turn the ignition on?

Last edited by rich17865; 2nd October 2014 at 20:27..
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