ABS activating on slow stop

[mussy]

Hi,

When I bought 80 number 3, aka Tarek the abs light was on. We traced this down to a damaged sensor on the front left hand side. This was duly changed and since then on slow stops the abs starts to kick in.

problem is this can be at stop signs, which can be quite disconcerting.

we have tried everything we can think of down to measuring the resistance of each sensor however to no avail.

Any ideas chaps?


Thanks as always!

 

[adrianr]

i wonder if its wear in the bronze bush allowing a little lateral movement in the hub?

 

[Chris]

The bushes do wear, but usually at the bottom so they go sort of elliptical. But remember that the CV is really held in place by the splines through the end drive flange which is bolted to the hub. OK the CV stub floats in and out a little bit but the bronze bit isn't really there to support the CV and drive shaft, it's there to stop the inside of the stub axle flange from wearing away. If the CV slines and drive flange get sloppy then this allows the CV to droop inside the swivel housing.

 

[Dave2000]

The bush does allow the CV to move out of alignment when worn, it is responsible for support when under load and turning the steering, if the bush did not take the load then the CV would try to move out of alignment, if it did not take any load then it/they would never wear out, and they do.

Check out this pic on my thread running on 'MUD', this is from my own car: http://forum.ih8mud.com/threads/my-lc-80-thread.365673/page-3

Seen this many times, the bronze bush/collar wears and the ABS trigger ring moves nearer and then further away from the sensor, this give a false reading, in my case the trigger would be as slowing and either turning the steering slightly (loading) in preparation to pull away if the road was clear or, just as I was slowing and hit a seam in the tarmac or bump on the surface.

I have on one occasion taken an ABS sensor out and found a 'spacer' below it? I have no idea why but it's removal stopped the false triggering, this was after replacing the bushes and flanges. Also check the trigger rings are not contaminated with iron filings from something that may have previously failed and repaired before your purchase, for example a busted CV or 'Birf' as they are often known as.

regards

Dave

 

[Chris]

Dave the shim is there to adjust the depth of the abs sensor. It's in the manual.

I do agree that the bushes wear, I have several, but I don't agree entirely that they are there to take the load. It's far too crude a set up to actually be supporting the CV all of the time. It guides for sure as the drive shaft whips and bucks about but it's not a bearing. The cv is held centrally by the end cap. It floats in and out a few mm as you turn corners but it also floats at the other end in the diff as well and in the bell of the cv. The splines on the end of the CV should be a smooth but snug fit in the drive flange and of course on the newer models the flange is deeper giving not only more secure drive but better support to the CV. The CV can't really move that much unless the splines / grooves are worn. The juddering you get on pulling up is a combination of all of those factors but more importantly a loss of the magnet force in the end of the sensor. Take a new sensor and pick up some metal. Now take one that is juddering and try and pick up the same load. The smoke leaks out of the sensors over time and also as bit of metal and grease build up on the tip, that lessens the strength too.

I don't have any pics, but I built up a hub off the vehicle so I could look inside and see what the various bits get up to when we're not looking. If I can find all the bits at some point, I might do it again and post it. I have the roller bearing conversion and the rollers are a pretty loose fit on the cv, the stub certainly wouldn't sit centrally in it and be supported by it.

 

[Dave2000]

I see where your coming from Chris and agree the splines should support the CV but, to be a true support they would have to be a press fit but of course they are not. This does allow the aforementioned 'slop', physics dictate the CV is under greater load when turning and applying load at the same time so the 'run out' if you like has to some degree be curtailed, hence the reason the bushes wear not only on the faces (correct in/out movement) but also on the inner faces. Toyota recognised this run out hence the reason the 'proper' Toyota oil seals in the axle tube are the 'floating lip' type, this allows the seal to 'follow' the inner axle shaft as it moves with the steering. Replacements tend to be the 'normal' oil seal and the axle oil leaks like a sieve into the CV grease.

I never noticed the shim in the workshop manual and gathered it was there to control the air gap between the ABS wheel and sensor, I can only surmise that the previous mechanic changed the CV and it was not up to spec hence the gap was too large for the sensor to 'read' the wheel correctly? My customer stated the false triggering was there from day one of owning the car, removal of the shim and all was well, bloody nuisance when you do not know the precise history of a car, and the LC's are not getting any younger.

regards

Dave

 

[mussy]

Thanks for all these points, I will look at all of them and report back. Thanks again!!

 

[Chris]

Dave once again I think we are violently agreeing here. There is movement in the splines and the bush is there to curtail that to prevent non replaceable wear. I agree on the seals which is why I only use genuine ones too.

 

[Dave2000]

Out of curiosity Chris (hope the OP does not mind hijack) did you see the wear ridges on the CV in my MUD pics, weird huh?

regards

Dave

 

[Chris]

Very strange.

 

[Dave2000]

^^^^^^^^^^^^^^^^^^^^^

My thoughts exactly!

regards

Dave

 

[IRLGW]

I had this problem. wheel bearing was loose.

 

[Ken Brenton]

I agree with IRLGW, a loose wheel bearing can cause major brake issues on an 80 series. On my old 80 (non ABS) in SA the pedal occasionally went to the floor on the return trip from a weekend rock crawling. Luckily the "SA Cruiser Whisperer" advised me on LCCSA to check front wheel bearing play first as it was a common cause.
I found some, not massive play, on RH wheel bearing, adjusted and hey presto brakes where fine again.
It's an easy first check to eliminate that possibility.