Brake problem with my classic mini
Discussion
I'm hoping someone can help with a problem I can't fathom out.
My mini started pulling to the left under braking recently.
Now I've had this problem before, caused by the pistons in the caliper seizing. Last year I ended up changing both calipers (using parts set aside for the MM), and while I use the car throughout the winter, I've never had them start to seize this quickly.
When I swapped over the wheels (back to summer tyres) the RH disc did look as if it wasn't being worked - it didn't look corroded, but wasn't the normal bright silver that the LH disc is.
But on pushing the pads back, both piston appear to move freely. I did this a few times (pads back, then press the foot pedal) and it did seem to make a slight improvement (but this may have been in my head!) then back to how it was.
To the extent that, on a clear straight road the car still pulls to the left and I can lock the left wheel but not the right (at the point of lock up).
I haven't tried pushing the pads back on the left. on the assumption that this side appears to be working normally.
Any ideas what the problem could be?
Tyre pressures checked, as have been the wheel bearings, ball joint etc. No brake judder either (disc seem to be true).
Thanks,
My mini started pulling to the left under braking recently.
Now I've had this problem before, caused by the pistons in the caliper seizing. Last year I ended up changing both calipers (using parts set aside for the MM), and while I use the car throughout the winter, I've never had them start to seize this quickly.
When I swapped over the wheels (back to summer tyres) the RH disc did look as if it wasn't being worked - it didn't look corroded, but wasn't the normal bright silver that the LH disc is.
But on pushing the pads back, both piston appear to move freely. I did this a few times (pads back, then press the foot pedal) and it did seem to make a slight improvement (but this may have been in my head!) then back to how it was.
To the extent that, on a clear straight road the car still pulls to the left and I can lock the left wheel but not the right (at the point of lock up).
I haven't tried pushing the pads back on the left. on the assumption that this side appears to be working normally.
Any ideas what the problem could be?
Tyre pressures checked, as have been the wheel bearings, ball joint etc. No brake judder either (disc seem to be true).
Thanks,
Either the rhs caliper is sticking, or it isn't getting full hydraulic pressure. I've heard of similar wierd symptoms being caused by delamination inside a flexible hose acting like a one way valve. If it was me, I'd get somebody to stamp on the brake pedal as if you were braking hard, hold the pressure on and crack the bleed nipple on the rhs caliper. If you get full pressure out and the pedal sinks to the floor, I'd assume the hydraulics were OK and look for a mechanical problem in the caliper.
phillpot said:
Twin piston calipers, no sliders.
Either one or both pistons jamming could cause the sort of symptoms you're seeing. What does the back of the rotor look like?How are the hydraulics connected for this caliper in terms of the position of the incoming line, the internal/external link pipe and bleed nipple(s)?
Random thought - my old Mazda 323 had a twin system coming from the master cylinder, so when the seals did go (often) I would only be braking on the front left and back right, I could not build up any pressure on the front right / back left.
Refurbed master cylinder fixed this - for about 3 years - now the car brakes on the front right / back left, the other two wheels hardly doing any braking.
My time to give the car away, your time to investigate the master cylinder?
Refurbed master cylinder fixed this - for about 3 years - now the car brakes on the front right / back left, the other two wheels hardly doing any braking.
My time to give the car away, your time to investigate the master cylinder?
I had exactly this, long time ago. Took me ages to work it out, at the time, but the hose had collapsed when I put a clamp on it. When I reflect back, it seems a shame I had to f
k up so many jobs in order to learn anything.
k up so many jobs in order to learn anything.GreenV8S said:
Either the rhs caliper is sticking, or it isn't getting full hydraulic pressure. I've heard of similar wierd symptoms being caused by delamination inside a flexible hose acting like a one way valve. If it was me, I'd get somebody to stamp on the brake pedal as if you were braking hard, hold the pressure on and crack the bleed nipple on the rhs caliper. If you get full pressure out and the pedal sinks to the floor, I'd assume the hydraulics were OK and look for a mechanical problem in the caliper.
Thanks for the responses and suggestions.
I'll be looking at this again this weekend.
To answer one of the above points, the rear of the disc did look to be in a better state than the outer face (as seen in the photo).
I did wonder if the problem could be master cylinder.
More detective work required.
I'll be looking at this again this weekend.
To answer one of the above points, the rear of the disc did look to be in a better state than the outer face (as seen in the photo).
I did wonder if the problem could be master cylinder.
More detective work required.
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