I know for a fact that the sensor that is coming up as faulty was pushed fully home because the dimple is scored from where the reluctor ring has been rubbing against it. It was only fitted 3 weeks ago. Flummoxed now.
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Datatek
Well-Known Member
So it has physical damage from being too tight in the bush. I had to hone the bush out on both my P38's to get a smooth sliding fit..
Datatek
Well-Known Member
The original sensors did not have a dimple, they has a flat sloped surface. The air pressure from the rotating reluctor ring is considerable and if the sensor is a correct sliding fit in the bush, it will push back and set the clearance correctly. Why do you think it has the spring cage between the sensor and the bush?
We are only talking about slight surface scoring, not worn through the stainless casing. I know the Wabco ones were dimple-less and the bore, cage & sensor need to be fully greased, which I did with the original set and the sensors went fully home with firm finger pressure. So do the dimpled ones need a gap or not or does the dimple act as the gap as per Kermit ? I might just try re-seating it first with a 1mm gap and then without. Wabco state no gap but a 1mm gap is acceptable. Either that or i'll let the guy sort it out who fitted the 2nd set in the first place.
Datatek
Well-Known Member
As has been said, they should be pushed in until they touch, there is enough flat surface for them to push back. I have not measured the resulting gap but they do definitely push back. I now have the aftermarket sensors in both my P38's and have had no trouble at all, but as I said I did hone out the bushes to ensure a smooth sliding fit. As you may be aware, the sensors rust in and are destroyed when removing them, the mounting bush has a thick layer of rust that is dimpled where the holes in the spring cage were positioned. Getting the bush smooth and rust free is important, I doubt any garage would spend the time needed to hone them out.
The coil wires are pretty fragile, I can only speculate that the dimple being constantly whacked by the teeth might cause failure.
I have used a lot of this type of sensor in other applications, usually the gap is a few thousands of an inch. I would expect a pretty poor signal with a 1mm gap. If I were to try and se the gap, I would go for about 10 thou.
Never had this problem with my 32 year old mk3 granada with abs - still on its original sensors which bolt in so air gap is pre-set. Only thing I did a couple of years ago is fit a new accumulator. The Ford or Saab or GM ones are no longer available but the range rover p38 Wabco one fits - as does the pump and pressure switch - Ford did own JLR 2000–2008 which is also why Range Rovers had heated windscreens as Ford had the patent until they let it lapse.
Datatek
Well-Known Member
I agree that the P38 ABS sensor mounting is crap, but it is cheap
Obviously not measured the forces involved, but i just assumed a sensor that was loose enough to get blown upwards would be too loose
Datatek
Well-Known Member
All I can say is that all 4 front sensor on my cars work and have been trouble free since fitting.
tomcat59alan
Well-Known Member
That's always been my experience.i had the lights come on once after a wheel bearing change and like you a soft tap with a nylon hammer did the job.
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If it makes you feel any better I've had my sensors out a few times and just pushed them back in and they work fine. As far as I'm aware they're original and mine's a '95.
And pray tell who's the lucky ladyIt's pi$$ing down here which is why I'm still in bed.
tomcat59alan
Well-Known Member
Why are you missing one?And pray tell who's the lucky lady
Datatek
Well-Known Member
A fine example of British precision engineeringThat's always been my experience.i had the lights come on once after a wheel bearing change and like you a soft tap with a nylon hammer did the job.
Ah, that would be a copper malet sir!A fine example of British precision engineering
I only replaced the originals because I had to replace the balljoints as they were an mot failure and you can't pull the hubs/driveshafts out of the carriers with the sensors in.
The originals were rusted solid into the hub carriers so had to be destroyed to remove them.. I would have left them in otherwise considering the grief i've had with OE replacements. Still i got my money back from the first set I ordered from Ebay and the second set fitted by the "landrover specialist" are guaranteed. Took the sensor out again this morning, cleaned it and pushed it back up to the teeth - no difference - don't get any warning lights but still get a brake pedal alternating between normal with brakes and then rock solid with no brakes. Taking it back tomorrow (again). 1st time he fixed the lights with a 2nd set of sensors but didn't fix the original fault I had after the 1st set of sensors.
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I'll see what the Landrover Specialist comes up with tomorrow with his diagnostic kit. He can check the waveform on his oscilloscope. If sensor checks out (5v dc at loom already has) then I think its going to be a case of pulling the hub & halfshaft and probably changing the reluctor ring. Can't imagine that it can be anything else.
