Bleeding Brake Problem

[Ashman]

RE040's, plus the car hasn't been anywhere except on and off the driveway. I don't fancy getting pulled by a copper and the car being taken away after all this work.

[ChrisHolmes]

Open question to all contributors, could the bad battery have caused "brain" issues within the ABS and or ECU?

[ChrisHolmes]

A dying battery can result in a corrupted ECU/PCM, if it results in someone attaching jump leads with the ignition still in the On position, the voltage spike can do nasty things.

[Ashman]

New battery on today and i removed the dcs and abs fuses, same problem. I think i'll try another caliper next, or at least checkout the caliper that's on now first.

[qwakers]

have you tried unplugging the abs module?

[ChrisHolmes]

My thought too in case there is wiring damage

[Ashman]

Nah i forgot, i'll give it a try tomorrow and let you know.

[mrspiller]

Try as many have said , unplug the main DSC fuse , plug code reader in , clear fault . As you hit 6-7 mph it will throw a fault .
Put the fuse back and try it agin , if it’s the same fault it’ll be power related , possibly speed sensor . Them speed sensors do take a bashing before they fail mind . If it’s not that you have an air leak . Could you get someone with a 3D printer to copy the brake fluid cap and pressure bleed it ?
If it’s already been advised I missed it ...


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[warpc0il]

Replicating the brake fluid cap doesn't work for pressure bleeding, at least not in my experience with the early reservoirs.

Rather than going for a vented cap, Mazda (or their supplier) chose to go for a bayonet cap with a soft gasket, and then allow air to enter by having a slot moulded down the thread of the tank.

I obtained a spare cap and tried all sorts of ways to achieve an airtight seal, in order to pressure bleed.
I was nearly successful, in that I did manage to build some positive pressure, only to have it then create a fine spray of brake fluid over the wing, roof, bonnet and engine bay, which had me running around like an idiot with a hose to wash away before the paint started peeling.

[mrspiller]

Just an idea


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[Ashman]

The bleeding problem has been solved (we hope), the problem now is the front left wheel locking up when the brake pedal is pressed. The abs sensor on that wheel has been replaced.

[Liam22]

I need a full post mortem on this so I can have closure

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[ChrisHolmes]

Question for all contributors.
Does a new sensor need to be “paired” in any way or are they plug and play?

[ChrisHolmes]

Plug-n-play on the abs.

It's the ESS that requires a 20-stomp reset to calibrate.

The abs is a similar mechanism but less concerned about absolute position.



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[geofftl1000r]

If it was the ESS holding the brake calliper on then there would need to be pressure in the hydraulic line to the calliper? So undoing the bleed nipple would release the pressure and free the calliper proving it was not a sticky calliper and the fault lies elsewhere?

[boosted]

Holy water and exocism of the Brake Demon....
Is all the front braking fluid going to this locking caliper...? I.e none getting to other caliper?

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[Ashman]

If that was happening then we wouldn't have had any fluid at the other calipers when they were bled, which we did. I've got another caliper so once that's fitted we'll know if is the caliper or not. I really hope it is...

[Ashman]

Caliper fitted, same issue. It seems to me now that both fronts are locking quick so i'm going to finish off bleeding the system until there's no air left (or as best as i can get it) and see how it is.

[PeteH]

If both front tyres lock up at low speed that's not a brake problem. It's the grip of the tyres. You may not have a problem at all. You should take the car for a proper drive (being careful of course). And, if you have cheap tyres, consider replacing them.

[ChrisHolmes]

Are you applying gradual pressure and then the brakes suddenly lock up? Hang on! Eureka moment here, how can the wheels lock if the ABS is working?

[PeteH]

Because this is all at parking speeds, and may be below the ABS speed threshold. Which is why I'm suggesting going for a proper drive.

[ChrisHolmes]

There's a complex relationship between the ABS (Anti-lock Brake System) and the EBD (Electronic Brakeforce Distribution).
ABS is in charge at medium and high speeds but EBD takes over at low speeds.

The only time I've seen similar symptoms, albeit on a totally different car, the guy had replaced the ABS distribution unit and got the pipes connected on the wrong ports. This meant that the system was sending all the pressure to the corner that was locked, and none to the corner that was still rolling.

[Ashman]

The only time I've seen similar symptoms, albeit on a totally different car, the guy had replaced the ABS distribution unit and got the pipes connected on the wrong ports. This meant that the system was sending all the pressure to the corner that was locked, and none to the corner that was still rolling.

I had that same thought but the brake lines are rigid and very hard to bend so they only really go in one spot.

I got another obd2 reader and this one worked. I read the codes and nothing showed up so i cleared anyway. I also did the 20 stomp and the little skid light went out so that's some good news at least (i think that was what cured it).

I agree that it needs to be driven but it's not legal. In order to drive it, it would need tax and mot, and the only way i can get it mot'd is to fix the issues, which i can't unless it's driven.

I'm considering taking it back to Mazda now i've changed everything. I only have the old mans Mondeo with a tow bar so i really can't take it any further.

[warpc0il]

You can legally drive it on the road, directly to a garage for a pre-booked MOT, or MOT repair, as long as it's not "dangerous".

[Ashman]

I just unplugged the abs module and tested the brakes and it seemed to go away. As soon as i plugged it back in and tested it locked up the front left again. So that seems to be the problem. £800 is a lot for an abs module from Mazda though...