Help. Cannot remove dead front ABS sensor.

[Laird Scooby]

Originally Posted by jpliddy

hi dave
yes the whole wheel bearing come out together . but the centre bearing part is in 2 half i did not realise this years ago when i replaced the front dust guards i pulled the wheel bearing off and not realising the centre bearing just came apart and ball bearing fell on the floor i panicked and got the unit all back together and put it back on the HUB it was a good few years ago now i suppose thats another job on the big list replace complete wheel bearing unit . but i think they are very expensive . the good quality ones anyway.

You have to be careful to avoid that happening Jim, not a great problem if it does but i've found using the spacer they supply in new hub/bearing assemblies to slide the hub/bearing assembly onto as you pull it off the stub axle helps prevent that happening.

Prices aren't too bad for them, you can pay silly money for them but i know i'd be seriously miffed if i spent a lot of money on them and they lasted no longer than a cheaper set. You always get a bit of warning before they go so with the cheaper ones it's easier to get replacements, even as a stop gap until the better ones are more affordable.

In fact, the cheaper ones are almost cheap enough that you could keep one on the shelf, if one did go unexpectedly quickly it's not a major headache to change it, just a bit time consuming. Think last time i had the hubs off, it took me half hour each side and that included removing the ABS reluctor ring and fitting replacements.

[griston64]

Fyi Gen Volvo hubs from FRF are £140.80 each + vat. Abs rings are £54.00 + vat.

You can buy SKF with Abs rings for just under £100 each inc vat

[Laird Scooby]

Originally Posted by griston64

Fyi Gen Volvo hubs from FRF are £140.80 each + vat. Abs rings are £54.00 + vat.

You can buy SKF with Abs rings for just under £100 each inc vat

Ouch!

I know they're pattern parts but PFV does the complete assemlies for £48.91 delivered including a new hub nut :

https://www.ebay.co.uk/itm/Volvo-700...y/293565332879

There are others around even cheaper but you start compromising with lack of ABS reluctor rings and so on.

[jpliddy]

hi thanks to all of you for support for that info .
hi mark who supplies SKF parts

[griston64]

Originally Posted by jpliddy

hi thanks to all of you for support for that info .
hi mark who supplies SKF parts

Hi Jim

A few of the online suppliers stock them. Autodoc was one https://www.autodoc.co.uk/skf/1362347

Someone on here bought cheapo ones and there was an issue with them

Cheers

Mark

[rogerthechorister]

The ABS light seems to be constant source of fun here! And it is a long time since I have been here.

Start by specifying vehicle: 1990/91 745 GLT with the B234F engine and OBD in little box between the windscreen and left suspension turret - a little probe you stick into holes.

Now the issue: For ages the ABS has sometimes had a little brrrr to itself at low speed. For some time the ABS light has been off with the ignition wholly off, came on when the ignition was turned on, went off when the engine was started, and then SOMETIMES come on when speed got to about 10 MPH. Stop car and re-start, maybe once, maybe twice, and the ABS light behaved fine. Since the backplates are mostly not there I thought sh1t in the tone rings and ignored it. Now the light does NOT go off when the engine is started. MoT fail looming.

Speedo behaved fine, so it was not the sensor in the rear diff. I thought probably one front sensor short or open circuit, or dud wire to it.

Car went in to allegedly the best welder in the Medway towns for unrelated work. He refused to try any sort of diagnostic and said I had to change the two front sensors. I let him do that using pattern ones from Braydons (now Trust). It made no difference.

The sources I have found online suggest that my particular OBD will not read ABS faults. That is odd as I am SURE I once saw an expert use it for precisely that.

So, first question.. SHOULD my OBD read abs faults and if so how?

Second question - blasted mechanic now says backplates have become an MoT fail - and I think he is going to have to pull the front hubs and tone rings to replace the backplates. Am I right and should I tell him to clean the tone rings and re-assemble to see what happens?

Third question - likely source of problem (1) idiot mecco has smashed the new sensors putting them in? or (2) in that the new sensors will have come with leads attached - connection inside front wing or other wiring and if so what? or (3) ABS brains near driver's right foot - possibly the plug (easy to do so try that first) or the ABS brains themselves (not I gather common)?

As far as the ABS brains and plug are concerned, mecco states driver's footwell is wet. That could be several things. I had it once before and it turned out to be the fit of the door seal to the top lip on the sill - filled the seal with mastic and job done. It is unlikely to be sunshine roof drains as the headlining is not stained. It might be windscreen, as the screen has cracked and is starting to delaminate at the top above the steering wheel. I'm pretty sure it is not heater control valve as there is no smell of coolant. It could be the scuttle panel drains (easy to see on a 760, not so easy on a 740 or 940 as the outer scuttle panel has to come off). But that damp could have caused corrosion on the plug to the ABS brains - or worse in the ABS brains.

What does the team think?

[Laird Scooby]

Originally Posted by rogerthechorister

The ABS light seems to be constant source of fun here! And it is a long time since I have been here.

Start by specifying vehicle: 1990/91 745 GLT with the B234F engine and OBD in little box between the windscreen and left suspension turret - a little probe you stick into holes.

Now the issue: For ages the ABS has sometimes had a little brrrr to itself at low speed. For some time the ABS light has been off with the ignition wholly off, came on when the ignition was turned on, went off when the engine was started, and then SOMETIMES come on when speed got to about 10 MPH. Stop car and re-start, maybe once, maybe twice, and the ABS light behaved fine. Since the backplates are mostly not there I thought sh1t in the tone rings and ignored it. Now the light does NOT go off when the engine is started. MoT fail looming.

Speedo behaved fine, so it was not the sensor in the rear diff. I thought probably one front sensor short or open circuit, or dud wire to it.

Car went in to allegedly the best welder in the Medway towns for unrelated work. He refused to try any sort of diagnostic and said I had to change the two front sensors. I let him do that using pattern ones from Braydons (now Trust). It made no difference.

The sources I have found online suggest that my particular OBD will not read ABS faults. That is odd as I am SURE I once saw an expert use it for precisely that.

So, first question.. SHOULD my OBD read abs faults and if so how?

Second question - blasted mechanic now says backplates have become an MoT fail - and I think he is going to have to pull the front hubs and tone rings to replace the backplates. Am I right and should I tell him to clean the tone rings and re-assemble to see what happens?

Third question - likely source of problem (1) idiot mecco has smashed the new sensors putting them in? or (2) in that the new sensors will have come with leads attached - connection inside front wing or other wiring and if so what? or (3) ABS brains near driver's right foot - possibly the plug (easy to do so try that first) or the ABS brains themselves (not I gather common)?

As far as the ABS brains and plug are concerned, mecco states driver's footwell is wet. That could be several things. I had it once before and it turned out to be the fit of the door seal to the top lip on the sill - filled the seal with mastic and job done. It is unlikely to be sunshine roof drains as the headlining is not stained. It might be windscreen, as the screen has cracked and is starting to delaminate at the top above the steering wheel. I'm pretty sure it is not heater control valve as there is no smell of coolant. It could be the scuttle panel drains (easy to see on a 760, not so easy on a 740 or 940 as the outer scuttle panel has to come off). But that damp could have caused corrosion on the plug to the ABS brains - or worse in the ABS brains.

What does the team think?

First of all, when you start the car, does the battery charge warning light show on position 2 before starting and does it go out once started? Do any other warning lights remain on?

Your ABS is too early to have self-diagnostics, you'll have to do things the old fashioned way.

Next thing to check, remove the under-dash panel and with the aid of a torch, find the fuel ECU on the bottom of the kick panel. Now look up, the ABS ECU should be above it and clipped to its bracket should be a relay with a 10A fuse in the top. Renew that fuse and see what you've got. Also check/renew fuse #9 in the main fusebox.

It's possible that your mechanic hasn't connected the new sensors correctly, sometimes they take more of a push to get the plugs home than people think.
If he has and renewing those fuses mentioned do't at least change if not fix the fault, obtain two 1200 Ohm resistors. Disconnect both sensors by the suspenion turrets (you'll need to follow the leads back to find the exact location) and connect a resistor in place of each sensor. Start the car and take a short test drive. If it's a sensor problem, the light should remain off until ~8mph (~12kmh), if so refit one sensor at a time until you know which is causing the ABS light to come on immediately.

As for access to the ABS ECU and plug, it's not easy at all. See how you get on with those tests to start with and we can go from there.

[rogerthechorister]

All the other dash lights behave perfectly. That 1200 Ohm resistor trick is a neat thought thought!

Puzzled about the 10A fuse though. Surely if that were blown then the ABS light would be permanently off, rather than permanently on as soon as the engine starts - or can you clarify why not?

Do you agree with me that if it were stuff in the tone rings the light would not come on until about 10mph?

[rogerthechorister]

PS, when you say the "plugs" do you mean the sensors themselves that need to be pushed into holes (with the O ring in the right place) or do you mean some other plug?

[Laird Scooby]

Originally Posted by rogerthechorister

All the other dash lights behave perfectly. That 1200 Ohm resistor trick is a neat thought thought!

Puzzled about the 10A fuse though. Surely if that were blown then the ABS light would be permanently off, rather than permanently on as soon as the engine starts - or can you clarify why not?

Do you agree with me that if it were stuff in the tone rings the light would not come on until about 10mph?

The 1200R resistors replicate working sensors that are picking up nothing,

Yes i can clarify why - at this stage it's probably easier for you if i give just the basic reason - there are other feeds to the ABS system, the transient suppressor fuse (10A on top of the relay) is only part of the potential problems.

See my comment about the resistor trick above and also in my original answer below.

Originally Posted by rogerthechorister

PS, when you say the "plugs" do you mean the sensors themselves that need to be pushed into holes (with the O ring in the right place) or do you mean some other plug?

See what i typed in my original answer below about where to fit the resistors.

Originally Posted by Laird Scooby

Disconnect both sensors by the suspenion turrets (you'll need to follow the leads back to find the exact location) and connect a resistor in place of each sensor. Start the car and take a short test drive. If it's a sensor problem, the light should remain off until ~8mph (~12kmh), if so refit one sensor at a time until you know which is causing the ABS light to come on immediately.

Note the positions of the ABS sensor plugs - connector plugs - on the suspension turrets. Inner wing areas.