Car brake repair

[Easy-X]

Had one of the brakes binding on the wife's car, front right/driverside: disc & pads totally cooked. I replaced those and to be on the safe side the caliper as well as it also looked pretty scorched (rubber dust seal melted away.) General advice also suggested maybe the flexi-hose that goes from the hardline to the caliper, pretty cheap so swapped that as well.

After the usual brake bleeding procedure we tested... feck! locked on like a limpet to a rock In frustration I pumped the brakes while my father-in-law made the teas. Blow me the brake unlocked! There was a wee bit of drag still but hey-ho new discs and pads but the sticky front giving us trouble at least wasn't locking up.

Drove the car back home (only 2 roads away) and the brake was definitely dragging. Nowhere near as bad as before but while the right was super toasty the left was barely warm. Dammit. I checked the rears and the opposite side (left/nearside) was toasty and the other cool. Double dammit.

AFAIK some modern cars run two diagonal brake circuits so I started trawling the various car-specific forums and TBH very little definitive help. Most ppl suggest the master cylinder (which is a twat to get to) or the ABS unit (which is a cunt to get to.) None of the forum threads with similar problems ever resolve into an actual solution

Master cylinder I could understand, given the previously mentioned symptoms, but the ABS? ABS should fail in such a way as to leave the braking system alone otherwise what? total electrical failure means your brakes lock on?! That makes no sense to me, sounds more like "dealer go cher-ching!" (and I bloody hope it's not that as they're silly expensive and most likely coded to the ECU.)

There's the hardlines I suppose but I think the probability of them failing is close to zero on a modern car. Maybe the hill brake assist gone wonky? I'd expect all the brakes to lock if it was that

I'll take another look this weekend but I'm thinking jack the front of the car so both front wheels are off the deck so I can compare the dragging brake to the working one and then loosen the hardlines that come from the master. If releasing the pressure there affects things I'd say it is the master.

Does one bother to rebuild car brake master cylinders like bike ones or just swap it for a new one?

BTW this is a Ford Grand C-max (same mechanically as a C-Max and the Focus.)
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[uberkron]

go and rockinghorse it.

accelerate hard up to 30ish. activate abs.

do this forward and reverse. exercises the valves in the abs modulator.

source, auto electrician with training and experience.
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i ride a zip 50 2smoke. It overtakes a hundred times a day.

[P.]

Had the same on the C-Max I worked on. I used the free Ford diagnostic to bleed the ABS pump and it sorted it.

Manually getting to the ABS pump is a cow, but the best place to start tbh

The ABS pumps fail on these too which weirdly jams a brake on. Had to send away for refurb which was agg.

[bugeye_bob]

As Paddy mentioned it maybe worth finding some software to operate the ABS Module, many moons ago Vectra B`s were notorious for ABS issues like Paddy mentioned,
The seals can fold the wrong way and air can get trapped,
What vehicle is it?

[P.]

https://forscan.org/home.html

You can also register for the free upgrade licence to do the ABS pump.

You also need a specific cable to switch between 2 modes. If you happen to be near to Maidstone/Bromley this weekend, I can potentially give you said cable.

[Easy-X]

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Just a little update. Looking at the FORScan forums it's pretty clear the software works better with a USB lead so I took a chance on a cheap one from eBay. Windows 10 hates it In the end I got it working with an old Windows 8 driver for Prolific USB serial ports.

Anyhoo, it connects to and recognises the car. I found an error but it was something about using an external memory card so probably GPS or infotainment related. I didn't try it but the ABS bleed option is present in the service menu for my car.

Quite surprised I don't need the extended licence (which is sitting in my inbox if needed) but judging from the forums people are doing really clever stuff like recoding diesel injectors so I suppose the ABS bleed is tame in comparison.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Easy-X]

Hooray! The ABS bleed procedure seems to have sorted it

To start with the brake pads at the rear were a bit worn so we thought "change them, then bleed as we're in that area anyway" to get the back-end out of the way. Oh, the rear pistons need winding in? Special tool required I suppose; yes and no. You can wind them in with just needle nose pliers if you crack the bleed nipple which is a detail none of our professional car mechanic friends cared to mention but we discovered getting frustrated with the proper tool. Anyhoo, crack bleed nipple, rewind piston, install new pads. Easy-peasy.

So then we're onto the FORScan software which, if you have the right cable, is piss easy to use. Connect to car, read codes, ECU data, etc. Then go to the service menu which crucially is what services can be offered by both the software and the car by agreement. ABS bleed procedure chosen and I said "brake hose changed" for whatever wheel we were at. Crack the bleed nipple, click "OK" then much mechanical noise generated from the ABS unit. With a laptop, with the right lead, with the right software and some knowledge of cars and computers.... errr... yeah, a straightforward procedure

We got round to the front left wheel before running out of DOT4 brake fluid Luckily a friend down the road had a gallon of the stuff but the interesting thing is that this wheel had loads of air in the brake line (bearing in mind it was actually the front right originally giving us trouble) and we re-ran the bleed procedure a few times for this one.

The said front right bled no problem at all and all that was left was to hurtle down the road! Only the first dab of the brake pedal was spongy (but new front disks, new pads all round) otherwise all performed surprisingly well. Although...

I did have an engine warning light which the FORScan software said was an ABS error (quelle surprise) but it went away on its own.

tl;dr Paddy if you ever head over to Box Hill at the weekend I owe you a chocolate milkshake
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[P.]