Best method to bleed the brakes

IMMX5 · Postby **IMMX5** » Fri Jul 18, 2008 7:44 pm

Chris, Phil
Pads are OEM - I've only 22k Km on the clock! The chamfer is there but the photo hides it as the pad is only ~4.5mm thick currently...

they must still have air in the system

Thats my guess too... :evil:

bled at the ABS unit

Would have hoped so - they had the car on the lift for near 3 hours - and closed the roller door so I couldn't see what was up! But in reality I guess not - they did a brake test and it \"Passed\" but thats not necessarily resulting in what we want.
Anyway (I must admit this is a new one on me) - how do you bleed the ABS unit? Presumably crack open the nut on the downstream side and depress pedal? (and catch the brake fluid before it makes a real mess!!)

Rear pads looked in better shape - no noticeable marking, some slight scoring - all of which came out with a light rub on wet & dry.

Now I just need to find an outlet for Valvoline brake fluid - seeing as thats what they used!

Postby **mx5racing** » Sat Jul 19, 2008 1:47 pm

they did a brake test and it \"Passed\"

Love the sound of this.... Did they do it on a skid test or just up a backstreet? Thank god it did \"pass\" or it might have ended up a couple of feet shorter.....

how do you bleed the ABS unit

the pipes screw into the top of the unit - 4 of them - one for each wheel. Just crack the nut and gently press down on the pedal (obviously 2 people needed). Do them in the same sequence N/S/R, O/S/R, N/S/F, O/S/F. They are marked on the ABS unit.

If you are still lacking pedal feel then bypass/exclude one caliper at a time and see if the pedal regains a solid feel. Easiest way is to crimp of the flexible brake hose with hose tool or if you dont have them a flat faced pair of pliers - dont use vice grips!! If their is any air left after the crimpt of section the pedal should be better. Obviously you only do this in the garage on stands/jacks and never drive it this way :oops:

I get a bit of black and rather thick liquid coming out from that hole.

the caliper is leaking internally.

....removing the rear 14mm nut to get to adjusting hex key...yours could be suffering similar fate Ian

NC doesnt have this adjusment anymore. Works as a self adjusting brakes with a screw type caliper piston.

Minh i'd try excluding the R/H/R caliper as per the details above and I think you will find your pedal will be back to its old self.

Ian, I will bring the other pads with me for you to try.

Chris.

Postby **mx5racing** » Wed Jul 23, 2008 4:43 pm

Ian not sure if this is helps but........

Just had a guy bring in his NC after having some brake pads replaced a couple of weeks ago by his neighbour, the ace mechanic. His pedal felt a bit \"squishy\" but it had been bled numerous times with no change.... Anyway we pulled the rear pads out to check and found the locating peg had not positioned in the caliper piston correctly and the pad was not square in the caliper. It felt very similar to your cars pedal and would explain why you are unable to find any air in the system.

Could be worth a look before you return to Mazda?

Chris.

IMMX5 · Postby **IMMX5** » Wed Jul 23, 2008 11:11 pm

Chris

I was thinking that what could be happening was that the rear pads were backing off slightly (too much) hence a dead space on depressing the pedal as it takes up the slack. I tried slipping in a ~0.005\" feeler gauge in on Saturday - pretty awkward but I reckon no luck getting it in anyway. So that may confirm the pad is in approximately the right position (not too far away) and not kept proud by the locating peg. (Apparently the clearance on the hand brake on old Alfa's was set up by having a 0.004\"/0.1mm clearance between the piston and rear pads). But the NC's are 'self-adjusting' anyway...

One suggestion made on Monday by one of the Lotus drivers - apparently he swings the caliper up so the bleed is at the highest point (Makes sense). So thats something to consider when I get the chance to pull the wheels off again.

I'm still trying to figure the next one out (which I didn't think of till driving the Corolla home last night and made the comparison) - I found that if I left foot brake (depress/pump 3 times or so) and then keep the pedal down whilst still maintaining momentum with the right foot on the accelerator I get the brake to lose the vacuum boost and it becomes a 'dead' pedal (still retarding but with no boost). I can't repeat that with the Corolla - at all! Have done the 3 basic checks set out in the (NB's) manual - would expect them to be the same for the NC and to be fair can't really pick anything - there are more checks but require fitting vacuum gauges. Could a light tear/puncture in the diaphragm give this squishy effect :?:

Certainly makes me think there is a booster problem anyway.

Still running on the pads you gave me on Monday - seem to have bedded in well (~80km at Wakefield!:D) and I do seem to have some of the feel back - even getting it to take higher. But it still feels 'squishy' :frown:

and pumping does get the pedal up a bit.

Wonder what the odds are on a defect on the brake lines - & some swelling under pressure! I guess crimping off like you suggested earlier could help ID that.

Much appreciate the help and input from you guys - great to be able to bounce ideas/suggestions around!

IMMX5 · Postby **IMMX5** » Tue Jul 29, 2008 6:23 pm

Update...

Comment on the brief test drive today - "doesn't feel too reassuring does it!"

Booked in to spend up to 3 days at the dealer next week on Mazda's account!

IMMX5 · Postby **IMMX5** » Fri Aug 08, 2008 6:34 pm

Final update:

Just collected the car - after 4 days! :frown:

But the brakes work as they should now....

They claim that the problem was the upper 'slide' (The manual calls it the 'sleeve' for the slide bolt) on the front nearside caliper was jamming thus preventing the caliper operating normally.

Oh well - should have picked that one..