Front wheel brakes lock up

HI, I have a '98 Frelander 1.8 petrol and it has just developed the most peculiar problem. The front right brake comes on and wont release consequently the disc oveheated.
I have replaced the caliper unit, pistons, pads, flexible brake hose and even the rigid brake hose to the ABS unit.
WHile I set this, I can spin the wheel, but as soon as I apply pressure to the brake pedal the brakes come on and wont release!!
Its like the brake fluid is going through a one way valve!!
I can release the wheel by releasing the connection of the brake pipe into the ABS unit (this does spray fluid all over!!), but as soon as I tighten up the connection and apply brake pressure it locks again.
Surely this is not a new ABS unit replacement, It only went in for new brake pads!!!

Emperorbilius said:

Surely this is not a new ABS unit replacement, It only went in for new brake pads!!!

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If when you first replaced the pads you just pushed back the caliper piston without opening the bleed nipple and letting the displaced fluid out then a any crap in the old fluid is now in the ABS modulator. :doh:

Thanks Chaser
Is bleeding the whole system an option or is the ABS Modulator in need of replacement?

I would go for a bleed of the system first - its cheaper than a new modulator and won't do any harm.

Emperorbilius said:

Thanks Chaser
Is bleeding the whole system an option or is the ABS Modulator in need of replacement?

Click to expand...

Yes definitely, I'd assumed you had already done that. Try and bleed with enough velocity to shift any dirt lodged in the valves of the modulator, particularly when bleeding the right front.
I think it may be knackered but good luck.

Further to the front brake saga...................
If I dont switch the ignition key to on, the wheel spins fine, I can apply the brake pedal, stops the wheel spin and it releases fine.
As soon as I switch on the ignition, and before I start the engine, and I depress the brake pedal, it locks and won't release.

Have now bled the system, font and back, the fluid flows nice and clean (new fluid each time) but still the thing refuses to work properly!!!

Anyone got a servicable ABS Modulator they are willing to sell (for a lot less than the new retail cost).... please.

Sounds like you've been a bit unlucky. The solenoid valve for that front wheel is being jammed open by some contamination. I've done a quick search re 'ABS modulator flushing' lots of info available. Might be worth spending some 'Google' time? Good luck.

Possibly a servo problem, as it works O.K. with the engine off ? There used to be a filter on the air inlet to servos, not sure if they still have them but if so it could be blocked