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[Kevin Wood]

Yep, if you can get a set of just the MC seals then that'd be worth a try, for the relatively small outlay.

You might well need the ABS ECU exercised using a Tech 2 when bleeding it after a MC change, though. I would bleed a little fluid through by loosening each of the outlets on the master cylinder one at a time to try to minimise the risk of this before bleeding the system, normally. This will minimise the amount of air that will get fed through the ABS ECU.

[petec]

Tanx, sounds like a plan! . I will try and seals before the weekend and have a go. I don't have access to a tech2 and hopefully will get away without needing one  but air does get into ABS unit is it possible to flush it through with a pressure bleeder (easybleed) or will airlocks remain in ABS.

[Michael2.6]

Have you tried the brake servo unit

this also makes the brake pedal go to the floor

[petec]

don't think its the servo because if I bleed the brakes everything is fine for a week or so then the pedal starts to feel progressively soggy.
 IMO it feels like air getting into the system and barring leaky pipes/connectors I think it could only get in through master cylinder seals or caliper seals. The calipers are all dry but have not taken the MC off to see if there is any seepage from the end so think this is the next most likely cause (hopefully).

[martin42]

I would say msater cylinder is failing,had the samething on my old astra van,,it would be fine for a week or two,then go soft or straight to the floor..

[petec]

well, put new master cylinder in last weekend, sods law that mine is a slightly unusual one and therefore more expensive. Took front calipers off, cleaned and painted them (hate working on rusty gungy brakes) and replaced front pads at same time.
I bench bled the cylinder and had no problem with air getting trapped in Abs unit which some folk had warned about. With engine off, pedal is now firm, near the top and does not sink, with engine running pedal is firmer and again does not sink, after few miles brakes are MUCH better than they have been for ages although it was good enough to pass an MOT before.

Brake sensor is an absolute pain, only one on my late facelift but very difficult to remove it from old pad without breaking it. I did manage to salvage sensor this time but will get new one next time I change pads

Next week its change the broken rear spring time...sigh

[Webby the Bear]

Well done mate. good diagnosis work from everyone.

these sensors, where do they attach from and to? the ones on my old banger have been cut and taped up so i cant see where they go.

[RobG]

Pic of sensor

Connector is the black one just to right of droplink arm

Sensor "pip" pushes into hole near clip at top of pad

[petec]

One prefacelifts and apparently early facelifts there are wear sensors on both front wheels, on my 2003 there is only one on the nearside front.

The wear sensor has an L shaped plastic? fitting on one end, about 1/2metre of lead and a 2 pin connector on the other. The connector it goes into is clipped vertically on the inner wing right behind the strut as you look at it through the wheelarch, about halfway up, its the black connector.
If your motor has HID lights the level sensor will be just to the right of it (its the unit with a short lever which goes down to the wishbone).

The lead has a couple of grommets which locate it on a bracket just near the connector and also onto the strut and there should be another clip halway along the brake pipe  that it clips into, finally you pop off the bleed valve cover and tuck the cable into the retaining loop for this...and put cap back on. basically the wire follows route of flexi brake pipe.

At the caliper end the sensor is, as I said an L shaped. imagine it as a capital L, about 3.5cm high with a foot of about 1.5-2cm. The cable comes in at the end of the foot (from bottom right of our L)  Half way up on the front vertical of the L there is a pin sticks out, and near the top at the back of the L there is a bump which is the sensor surface.
Looking at the nearside caliper from above the sensor fits on the inside pad, the pin pushes tightly into the rivet which holds the antirattle spring (L is upside down with wire leading out towards strut, bump on sensor is facing disc and whole thing sits in recess in pad. When pad wears down the bump touches disc which wears it down, a link inside bump is broken which triggers brake wear signal. Problem is the sensor is a tight fit in the rivet head and is difficult to remove without breaking it. I managed by supporting pad and gently drifting pin out from reverse side but its probably worth getting a new one if you are changing pads, you will need a new one anyway this time but nothing worse than getting motor to bits and finding you need extra part...with no transport to get it  

[petec]

nice one robg, a picture certainly is worth a thousand words