Brake pedal dropping to floor (non MR2)

[Bossworld]

I've done something stupid and I can't figure out what.

The Mini's brakes have always been fairly poor, took it to a garage last week and they said they're fine and it's just because it's a larger car.  There was a slight squeak so I thought I'd take the opportunity last night to strip them down and ceratec all the sliders/stick coppaslip on the back of the pads.

Reassembled fine. I've just tried to take it out and the pedal goes to the floor with only moderate resistance and braking is very poor.

Everything is torqued up correctly, the master cylinder still looks full of fluid.

I took the cap off when I pushed the pistons in very slightly, then put the cap straight back on.

There appears to be pressure if pumped while the car isn't running.  If the car is running, pumping repeatedly makes the pedal firmer but it can still be pressed all the way to the floor.

Am I mising something obvious or has something gone wrong along the way?

Thanks in advance

[Carolyn]

Somehow, you've got air in the system

The brakes need to be bled.  Start at the corner furthest form the master cylinder.

Have you bled brakes before? (Don't want to tell my Grandmother how to suck eggs!).

Keep an eye on the fluid level as you go.

[Bossworld]

Somehow, you've got air in the system

The brakes need to be bled.  Start at the corner furthest form the master cylinder.

Have you bled brakes before? (Don't want to tell my Grandmother how to suck eggs!).

Keep an eye on the fluid level as you go.

I have yes, thanks C and no offence taken. I've never previously had to bleed after what I thought was effectively a glorified pad change but will certainly try that next.

[Bossworld]

Bled them, they're better (in that they actually stop the car now) but I'm not convinced they're 100%.

I think the master cylinder is OK (I've read apocrphyal stories of flipping seals when pushing pistons in but seems unlikely).

Only thing I can think of is that there's either air in the ABS unit (but I got it to kick in a few times under very hard braking) or the brakes weren't sliding before and now I've got more modulation (seems unlikely).

Going to sleep on it and take the MR2 in the morning for a comparison

Edit: took it out again this morning, seemed better than last night but it's still a bit spongey. I'll try another bleed and see if I can figure out the BMW abs bleed. Still at a loss as to how air got in (didn't really see any come out when bleeding other than as it filled up the tubing).

[Bossworld]

Bled the whole lot a second time (me pressing the pedal with a one way valve eazi-bleed) and ran the ABS bleed routine too.  Seems to be back to normal.  What a pain in the backside INPA/ISTA-D (BMW diagnostic and service software) is.

Thanks Carolyn.  Still don't understand how air got in but it hopefully won't need touching again for a couple of years.

[Bossworld]

Sorry I'm bringing this one up again so will look like a complete newb.

Different car - Changed the rear left caliper, also managed to install a new bleed nipple on the front left which had been seized in there for a long long time.

Bled all the way around with a one man kit, took it out, must still be air in the lines.  Did it a second time; the car felt as it did on Friday (IMO) but I'm used to mine being razor sharp.

Bled a third time, got a couple more bubbles out.  The sound bleeding the rear two was different - even with no air coming out through the hose, there was almost a 'sssshhh' noise as the pedal was depressed.  Didn't get the same on the fronts (either side, I know it's a diagonal setup).

The pedal is rock solid with the engine off.  The master cylinder isn't going down and I see no obvious leaks.  I re-used the rear-left hose but fitted new copper washers either side of the fitting, removing the remaining half of the factory clip washer (on the second run through - whoops!).  No visible leaks around the caliper and once the bleed nipple is tightened, the pedal goes solid.


——

Edit: Had a text to say that everything is fine. Job is (hopefully) a good'un