Potential brake issue?

[len_beach]

This seems to be a problem that afflicts every one of my cars, I've never worked it out.

When I really anchor on when the brakes are cold, emergency stop etc, the pedal goes rock solid, the brakes make a very metallic grating sound and stopping power is practically non existant. It has only happed a few times and if I lift off and plant my foot again, all is good and my internals are ripped from their mountings.

The calipers are all OK, I rebuilt the NS front around 6 months ago due to a seized guide.

The pads are Mintex Xtremes with plenty of life left in them as they were fitted 6 months ago. They were bedded in correctly and have plenty of bite so these aren't the issue.

The disks are OE and were again fitted around 6 months ago.

I really can't work out what the issue is. I had the same problem with my old Chavalier and put it down to cold disks/pads and whacky ABS.

 

[Josh@Renparts]

Not just surface rust on the calipers? most pads need a little heat to be effective i usually find, but usually find even from very cold to have a good degree of stopping power.

 

[len_beach]

Not just surface rust on the calipers? most pads need a little heat to be effective i usually find, but usually find even from very cold to have a good degree of stopping power.

It could well be, I never thought of that. The last time it happened, I pulled out of my local motor factors and practically straight onto a country road. I gave it a bit when a Pheasant ran out in front of me. Intially I had the issue, after that, no problems at all.

It could just be heat and slight oxidisation but would this explain the solid pedal?

It almost sounds like the sudden acceleation is drawing air into the servo.

 

[Josh@Renparts]

have you bled your brakes recently? or changed the fluid at all?

 

[len_beach]

Did both 6 months ago when I fitted braided lines, new disks and pads. The issue was there before but now you mention it, it could well be an air pocket.

 

[Josh@Renparts]

i would definitely re-bleed, see if it makes any difference. usually air makes them spongy rather than hard. just make sure you give the brake pedal a good push after starting the ignition.