ABS operating occasionally

[kernowman]

Hi, as a relatively new Explorer owner, can I please ask for views from members before I get too involved with ABS codes. Firstly, I have on order a simple hand-held OBDII code reader, which I assume will not read the ABS codes, only the engine management codes, so it looks as if I need to go to my local garage.
My ABS light goes out correctly after about 3 seconds after starting and does not come on again. However, occasionally at speeds up to about 10mph the ABS operates on both light and heavy braking, with quite a noticeable pull to the right. I say up to about 10mph - haven't the courage to try above this speed so run with the ABS fuse pulled and the light permanently on. With the fuse pulled, the vehicle stops perfectly with no ABS and does not pull to the right.
Has anybody experienced this type of fault? - on searching the forum most faults seem to be with the ABS light coming on due to sensor problems, and the ABS then switching off.
Regards,
Richard

 

[blueka]

Yeah, I have the same problem, I've disconnected the ABS altogether and I've driven without it for 2yrs without any problem at all. You'll probably need to replace one of the sensors but the ones on the front are part of the hub assembly.

Si

 

[kernowman]

My problem is that they have failed it on the MOT because the ABS light is on, and will not pass it with no light either, unless it comes on for a short period after starting. In other words, if ABS is fitted, it must be seen to work properly.

 

[blueka]

Mine passed the MOT like that, I just took the bulb out.

Si

 

[kernowman]

Tried that first time it went for MOT, but they failed it because the light was not working when the ignition was first switched on.
Richard

 

[kevin p]

Is it worth risking taking it to another tester that might not notice?

 

[kernowman]

That was my initial thought, but rather than risk losing another MOT fee, I think I will go ahead and try and sort the problem. I have access to a new front hub with sensor - will try that on the left. My logic is that because it is pulling to the right when the ABS operates, the fault should be with the left sensor as this wheel is being braked normally. However, could be wrong on this one. Any comments on my logic would be appreciated!!!

 

[blueka]

Sounds logical to me..

Si

 

[kennyh]

Richard

I'm pretty sure I know what your problem is, as I've just fixed the exact same problem on mine; which also failed it's MOT due to this and other issues.

It's (probably) the front ABS speed sensors. My problem was that the ABS would kick in when coming to a stop and at low speed the ABS kicked in and it ended up increasing the stopping distance. In fact I crossed the lines at junctions a few times and scared the sh*t out of me.

At first I just disconnected the two front ABS speed sensor cables under the front wheel arches (near to the bumper). That fixed it, but the MOT tester would not pass the vehicle with a warning light on.

So, I purchased two 2nd-hand speed sensors from Explorerparts in Newport for only a few quid, and then I replaced the original ones. Sorted!

Problem went away.

So for just a few quid (and approx 2 hours work to strip the front discs off to remove/replace the speed sensors) I got it sorted. My MOT garage was quoting me hundreds of pounds to even have a look at them.

Of course, this may not be the problem in your case, but I suggest you give that a try to begin with.

Also, the nice chap at Exportparts suggested cleaning the teeth inside the hubs when you pull the speed sensors out, as they sometime get full of gunk which affects the performance of the sensors. I don't think you'll need to replace the hubs.

Cheers
Kenny.

 

[kernowman]

Kenny, you have given me great hope - just waiting for some decent weather now to give it a go. I definitely had the wrong idea with regard to the speed sensors - had the impression that they were not removeable from the hub, being made as an integral part.
Can I assume from your conversaion with the chap at Explorerparts that the hub can be dismantled for cleaning the sensor teeth?
It does seem a bit improbable if you cannot dismantle the hub, or at least draw the bearing so it can all be cleaned properly. However, I will quote Haynes 1991 thru 2001 Explorer manual which, for 1995 and later FWD vehicles, says "Note: The hub and bearing assembly is a sealed unit and isn't serviceable. If it's defective, it must be replaced".
Will keep you posted next week with how I get on - this is the only thing holding me up with the MOT.
Think you have been lucky, Si, with getting through the MOT with the bulb out - my MOT guys were aware straight away about bulb removal because the light has to come on for a few seconds when the ignition is turned on. They are also aware of another trick regarding ABS on vehicles and that is to wire the ABS light to the oil pressure switch so it goes out when the engine is started. Strange what people get up to - wouldn't really recommend this one!!!!
Thanks to everybody.
Richard

 

[blueka]

well.... it got me thru till I can save enough up for 2 new hubs...



Si

 

[kennyh]

I definitely had the wrong idea with regard to the speed sensors - had the impression that they were not removeable from the hub, being made as an integral part.
Can I assume from your conversaion with the chap at Explorerparts that the hub can be dismantled for cleaning the sensor teeth?

The speed sensors are bolted to the outside of the hub (on my '98 Ex anyway) - you need to remove the discs, and brake disc shield to get access.

Once you've pulled the sensors out - you can see the sensor teeth down the hole the sensor came from. As suggested by the guy from Explorerparts - you can clean the teeth by sticking a bit of rag (or I used kitchen roll), down the hole and then spin the hub to "wipe" the top of the teeth. It's not exactly deep cleaning the sensor ring, but it did work for me, in combination with replacing the sensors.

I did have one fiddly bit, which was when I removed the old sensors, it left a plastic tube in the hole (which was actually the outer sheath of the sensor). I then had to use a drill (by hand) to pick the plastic sheath out in order to get the newer ones in.

Also, make sure you give the hub a good wire brush all around the sensor before removing it, as you don't want bit of rust/dirt falling in to the hole while your working on it.

I was SO happy that swapping the sensors fixed my problem; the thought of a major ABS system fix would have been a nightmare.

Cheers
Kenny

 

[kernowman]

At last, all up an running OK with no ABS problems - have put the fuse and bulb back and my light now goes out properly and the pedal is normal. Nearside sensor was showing correct resistance, but had a very weak output. Being the meanie I am and not wishing to use secondhand, I managed to purchase two new sensors from the states on eBay - final price $32.00 the pair plus postage. The worst part of fitting was removing the remains of the old sensor plastic tube that Kenny mentioned that was left in the hole, trying not to let any crud or rust drop down inside. Rest was just common sense and a bit of effort to free the caliper bolts. Off for my MOT next week. Final opinion is that the job sounds a lot more difficult than it actually is. Thanks everybody for your help and encouragement.
Richard

 

[kennyh]

Glad I could help, and good luck with the MOT.

It's feels good when you can fix things for a fraction of the cost a garage would charge


Cheers
Kenny.