Traction Control problem

[phil&liz]

Hello all,
Traction control (TC) is faulty and is only functioning on the front left and the rear right wheels. I proved this by performing the following test:
? Without CDL and handbrake activated one wheel is raised, 1st gear selected and motor idling. The raised wheel will spin and TC will not activate. This is OK and is functioning correctly. When the revs are slowly increased TC activates and should then start to apply brake force on the raised, spinning wheel. This does not happen to the front right and rear left wheels.
I have manually bled all wheels. And preformed Power bleeds and Modulator bleeds using a nanocom. I'm not sure how to perform the power and modulator bleeds but did them with one of the caliper bleeds open. No brake fluid was expelled when performing these bleed functions. I then performed the ABS bleed test on all wheels. Only the front left and the rear right expelled brake fluid during these wheel tests.
The modulator has had the shuttle valve repair option B done to it and there are no faults being generated.
All recommendations, thoughts and comments appreciated.

Phil

[PhilipA]

How does your HDC work.
If only on left front I would think it would pull heavily to the left.
I wonder if a pressure bleed may fix the problem.
When I did mine about 1year ago I did the purge and then pressure bled. AFAIK the ABS works perfectly and I exercise the HDC every month or so.
Regards Philip A

[Outback 1]

It may have option b done but option b will not stop the shuttle valve from failing i would be checking this first if you look in the good oil I think the procedure for testing is in there iirc

Sent from my SM-G900I using AULRO mobile app

[phil&liz]

The shuttle valve has tested OK 3k ohm with no brake, 2k ohm with some brake and 1k ohm with a little more brake

[phil&liz]

performed the the modulator bleed again. This time I noticed brake fluid was expelled form the front right and rear left wheels but not from front right or rear left wheels.

[phil&liz]

I don't use HDC much. I agree it would also be affected.
Thanks

[ballbag]

Keep on bleeding. Follow the power ABS module bleed procedure then bleed the offending caliper by keeping nipple open and pumping pedal until you get flow, then bleed as normal. 2 man, 2L fluid, 2 hr, 4 beer job.

[ballbag]

...bleed offending calipers in correct order for RHD vehicle.

[phil&liz]

I don't know the correct power bleed procedure. Can someone provide it please?

[sierrafery]

The question is that do you see the TC light on dash while performing these tests just that the wheels are spinning or no warning light activity either? ... i'm asking cos it's possible that the TC to not work from stationary cos the SLABS is in sensor sellf check mode after ignition untill the vehicle exceeds 10km/h... the TC is conceived to use brake intervention if it detects a wheel accelerating faster than the average and while the vehicle is stationary it might not work as expected... drive the vehicle as to exceed 10km/h then dont turn the ignition off and perform the tests again... though if the TC light is active just no brakes on the spinning wheel then it's possible to be air in the system

[Pedro_The_Swift]

I don't know the correct power bleed procedure. Can someone provide it please?
by Nanocom?
From The Good Oil--
http://www.aulro.com/afvb/discovery-2/131263-d2-abs-modulator-power-bleed.html

or power bleed by another method?

[PhilipA]

I bleed mine with a pressure bleeder ie a pot with a pump that pressurises the whole system by attaching to the filler of the master cylinder.
I have to use an adaptor which chains around the master cylinder because bloody Land Rover changed from the common one on RRC to one that nobody has an adaptor for.

Regards Philip A

[phil&liz]

Yep. Power bleed use a nanocom

[Pedro_The_Swift]

Phillip, will that still work with the modulator inbetween the pot and the nipples?

its very easy to trick the modulator to work.

[PhilipA]

Phillip, will that still work with the modulator inbetween the pot and the nipples?

its very easy to trick the modulator to work. __________________AFAIR It is listed in the WABCO leaflet on bleeding the system.
Regards Philip A

This post has the WABCO how to for pressure bleeding and manual bleeding.


D2 ABS Modulator power bleed

[phil&liz]

When testing traction control TC lamp was on and the modulator pump could be heard.

[Pedro_The_Swift]

that should rule out a faulty modulator.

is the nanocom-power-bleed a one person job?

[phil&liz]

Hello all,
I have fixed my problem by replacing the modulator. Will try to determine what the problem is by dismantling the modulator.

Thank you all
Phil

[kelvo]

that should rule out a faulty modulator.

is the nanocom-power-bleed a one person job?

Yes, but you have to be quick moving from the Nanocom to the bleed nipples. Easier with 2 people.

[Pedro_The_Swift]

can be a 1 person job doing it another way--
still using the modulator,,

[rusty05]

Hello all,
I have fixed my problem by replacing the modulator. Will try to determine what the problem is by dismantling the modulator.

Thank you all
Phil


Had the 3 amigos popped up at all?

[phil&liz]

Found the reason why TC was working on only two wheels. The main spring in the modulator pump for the secondary circuit had shattered into four pieces. This resulted in the piston not returning to its normal, extended position.
Picture 3, ABS pump with the broken spring. Note the piston is retracted.
Picture 1, the shattered spring
Picture 2, a dismantled ABS pump with an intact main spring

[ballbag]

Not good.

[PhilipA]

I wonder how many are like that?

Regards Philip A