E30 Zone

Left front caliper keeps getting stuck on hard but is intermittent. Recently finished rebuilding the car which included new master cylinder and flex lines.
I've stripped/cleaned/greased the caliper which hasn't helped, I can push the piston in by hand.
Usually by the time ive got home and got the wheel off its freed itself off so cant test the pressure with the bleeder.
Would be great if anyone has any suggestions??

You haven't mentioned the guide pins, but I expect these are well greased if you've just rebuilt.
Apart from that, you've covered all the usual reasons, so this is one of the rare occasions I'd recommend diagnosis by replacement. Trying a different caliper would be the first thing I'd do.
Any ABS on this car?

Guide pins are in good condition and operating smoothly. No ABS. Ok yeah I think its best I try a different caliper first, would be unfortunate if its the new master. I was thinking would it effect both front calipers if it was in fact the master? Thanks Brian

E30 has front/back split for the brakes, not diagonal split, so the fluid pressure that goes to one front caliper is exactly the same as that to the other. Separate ABS valves, if fitted, which could conceivably cause what you're experiencing, but you don't have ABS.

Problem solved After rechecking the caliper, hoses etc I took the car for a drive sure enough the caliper stuck on and could barely move for some reason I decided to lift the brake pedal with my foot as soon as I did the brake released, so after some slight pedal adjustment its been great car feels fantastic now.

If this was the problem, it should have affected the other front caliper equally. One question answered and another one posed.

Could the piston in the master been travelling far enough to cover one of the ports?

HairyScreech wrote:Could the piston in the master been travelling far enough to cover one of the ports?

Brianmoooore wrote:E30 has front/back split for the brakes, not diagonal split, so the fluid pressure that goes to one front caliper is exactly the same as that to the other.

The fluid for each front caliper leaves the master cylinder via two separate ports, but these two ports are just plain holes into the cylinder bore, and are very close together inside the bore.
They are right at the front of the bore, in an area that I wouldn't expect the piston to go anywhere near in use.

Good point, that's what I get for posting off the cuff at lunch. with that said there is no certainty that the orifices are in the same place inside the cylinder.
Having just checked mine the fronts are separate at the cylinder. (3 ports in Y split)

Is the RH caliper moving properly? could both have been sticking to a certain extent but the RH less noticeable thanks to being sticky/not fully bled?

Do you have a friendly MOT center that would let you put in on the tester?

I thought there were only two outlets from the master cylinder, one for the front and one for the rear?

Ben

Nope, 2x 1 front and 1x rear line.
Fronts are not on a T piece.

Edit - the 2 fronts are at the servo end and the rear further out iirc.

Edit Edit - That said I think the ABS stuff might be 2 line, I now the E36 uses a 2 line ABS/master.