Its been a while (years) since I have messed around with brakes on a MX5. All pads and discs were replaced last October when the car was MOT’d (ironically, at my request, because they hadn’t been touched in a long while).
The offside front caliper was seizing on just before Christmas. Fnally got around to looking it over. I thought at first it was a sliding pin, the top one was a bit dry and was a struggle to get out. So I thought it was a victor to lube up the pins with the right grease, and have a caliper that beautifully slid on the pins. Reassembled, pump the brake, front locks on. It will turn with a bar across the studs, but there is clear resistance.
So dissambled again, took off a pad, reassembled, and gave the brake pedal and light pump to push out the piston a little. Then I pushed it back in. Reassembled as before. No change.
So I think the caliper needs replacing; it was probably replaced 5-10 years ago (Brakes International recon). Piston doesn’t look rusty at all, except on the edges that contact the pads. But there was a lot of resistance to pushing it back.
I have brake line clamps. Can I just replace that caliper, and just bleed that corner, rather than a 4 wheel caliper. My garage is too small to get around the car, and I have a deeply sloping drive. I think I might need to “bench bleed” the new caliper if I did this.