I have a problem with the front brakes sticking on.

 

I have replaced the rear calipers with new ones and also fitted some braided brake lines.

 

The front calipers have been stripped down and new seals and dust covers fitted, all the bores and pistons are good condition.

 

I dismantled a good master cylinder and re assembled without using a refurb kit as it all looks good.

 

The brakes continue to stick on even when cold so I'm guessing there is either a problem with the original rubber front hoses (both sides failing at the same time would seem odd)

or maybe something wrong with the ABS pump??

 

I've also loosened the nuts on the master cylinder to clear it from the servo rod, still binding.....

 

Any suggestions welcomed

 

Thanks

Before replacing the caliper piston seals did you thoroughly clean the grooves the seals fit in?

Also, did you soak the seals in brake fluid before refitting them and the pistons?

Yes I cleaned the bores and grooves and assembled with plenty of fluid.

Seems that all 4 pads and all 8 pistons aren't returning.

Thanks anyway

To rule out pressure in the system holding the pads on you could try opening the caliper bleed valves.

Are the pads new? There should be some movement between them and the caliper body, is there?

Make sure they are not binding. Can you jiggle them about?

 

This is the FSM for the front caliper and shows assembly order (pads,shims etc):

 

http://www.300zx.co.uk/tech/manual/manual/br/012.gif

That was my next move to release the pressure, the pistons are free as I am able to push on each pad with a screwdriver and this will push each pair of pistons back in until there is clearance.

The pads are only part worn and the discs have a very minimal lip

I think I'll also take out the shims and see if it makes a difference as if either is warped then this might explain the symptom.

Thanks

I had this years ago, stripped and replaced various bit, turned out to be collapsed front hoses. (If they're old and

have been clamped with hose clamps while calipers have been off, then that might be your prob)

As mentioned, if they free off when bleed nipple is opened, it might point to hoses.

I think it probably is the hoses it was only the fact that both discs lock up.

I have a pair of goodrich hoses for the front but they are missing the connectors on one end otherwise I would have fitted them when I did the calipers.

If the hoses are not the problem, then check the free play at the brake pedal, the rod is adjustable and if wrongly adjusted will not release the brakes fully.

 

 

Jeff TT

Have released the pressure in both calipers and still binding also just checked the free play and have 3 or 4mm.

Could the prob be with the ABS pump?

If you've released the pressure in both calipers through the bleed nipples and they are still binding then to me it would still point to a sticking piston/s. I know you've had them apart, but really can't see any other explanation. When you say they are sticking, are they offering proper resistance or is it just the noise of the pads very lightly touching the discs because I don't recall these brakes having any thing to push back against the pistons when released.

Front hoses replaced and now cured.

Guessing that the pistons need to 'rock' back and forth in these straight cut seals and need a few miles to settle which explains why they were still stuck on when the nipples were opened...