Brake Master Cylinder
Discussion
Hi guys
Long time lurker, and would greatfully appreciate any help and expertise from the PHers.
I have a 2001 1.6 mazda 323, the car means a lot to me as it's my first car that I've had for ermm 4 - 5 years now and prior to that it was my parents - so been in the family all it's life. We've been a bit anal and have a book which lists every single fill up, mpg between fill ups and every single service, MOT etc. etc. So it's quite good for looking at the history of the car!
Anyway the story goes:
+ Feb 2006 @ 39k miles, F/OS inside edge disc was warped, so front discs changed (under warranty I think)
+ April 2009 - car's now in my ownership (46k miles)
+ July 2011 @ 70k miles, I noticed F/OS disc was sticking when I did a quick oil+filter change. Long shot being it released eventually, so as long as the driving didn't involve much braking, it's ok. Drove to the Alps and back - very fast round alpine hairpins to avoid using brakes.
+ End July 2011 @ 72.5k miles, rebuilt front calipers with new seals, new flexi-hoses, new discs, new pads and flushed the brake fluid system completely. Brkaes never felt better, no dragging or anything, lovely jubbly. I thought this had even sorted the warped disc issue from Feb 2006.
+July 2013 @ 87k miles (just last weekend) - drive to screwfix with my old man so I can buy some jubilee clips to stop some exhaust heat shields rattling on my mothers car, 4 very sedate miles - no hard braking and probably didn't go above 45mph anywhere if I was lucky, park up in screwfix car park, and smell cooked brake. F N/S was stone cold and I could touch the caliper and disc etc, F O/S I couldn't even touch the wheel it was so hot. What was weird was that I didn't feel the car pull me to the right or anything. Anyway, so what I did was buy some allen keys and a G-clamp from screwfix as I was there, jacked the car up, took wheel off, undid caliper and pushed the piston back, waited for everything to cool down, and limped home using only the handbrake.
So after that, as I rewound the piston easy peasy, and I'd rebuilt them 2 years previously, I thought it unlikely it would be the calipers again, and in fairness when I rebuilt the calipers I didn't spot anything that looked bad. After lots of thinking/research and discussions, I decided it most likely to be the brake master cylinder, and that costs £267 from mazda. Anyway, I've taken the brake master cylinder apart, and can't find anything that looks odd.
Brake Master Cylinder by zippyonline, on Flickr
I then had another look at the master cylinder with a bit of a critical eye. Here are three pictures to show what I found:
Master Cylinder looking broadly from above, as if the reservoir was there.
P1170943 by zippyonline, on Flickr
Master cylinder reservoir joint closest to the pushrod/servo. Notice one hole which is a pinprick into the master cylinder, and the large hole which is located on the shoulder where the rubber seal/join bushing seals the feed from the reservoir.
P1170941 by zippyonline, on Flickr
And here is the master cylinder reservoir joint furthest from the pushrod/servo. Notice one hole, not on the shoulder of where the rubber seal is.
P1170940 by zippyonline, on Flickr
From what I understand (having just learnt in more detail off the tinterweb how a brake master cylinder works), the small pinprick hole is the fluid intake and return port which feeds off to the callipers, and the larger hole is the equalisation port behind the piston seal in the brake master cylinder so a vacuum is not caused. SO missing a hole on one of the circuits sounds like a possible cause of my sticky brake - but having not seen any other brake master cylinders apart, I'm not 100% certain and don't know about design variations and my particular car.
Given the history of the car from new and the constantly recurring F O/S sticky brake, I have a sneaking suspicion that this may be a manufacturing fault and the cause of my problems. I don't know which way round the brakes feed and it's not the easiest thing to follow round the car given it goes through the ABS module, but i'm guessing each piston on the master cylinder feed brakes diagonally opposite corners rather than front and rear or Left and Right as that's the norm as far as I'm aware.
So any advice gratefully received. If anyone has a master cylinder or taken one apart to compare, I'd really appreciate that too.
Thankyou very much.
Long time lurker, and would greatfully appreciate any help and expertise from the PHers.
I have a 2001 1.6 mazda 323, the car means a lot to me as it's my first car that I've had for ermm 4 - 5 years now and prior to that it was my parents - so been in the family all it's life. We've been a bit anal and have a book which lists every single fill up, mpg between fill ups and every single service, MOT etc. etc. So it's quite good for looking at the history of the car!
Anyway the story goes:
+ Feb 2006 @ 39k miles, F/OS inside edge disc was warped, so front discs changed (under warranty I think)
+ April 2009 - car's now in my ownership (46k miles)
+ July 2011 @ 70k miles, I noticed F/OS disc was sticking when I did a quick oil+filter change. Long shot being it released eventually, so as long as the driving didn't involve much braking, it's ok. Drove to the Alps and back - very fast round alpine hairpins to avoid using brakes.
+ End July 2011 @ 72.5k miles, rebuilt front calipers with new seals, new flexi-hoses, new discs, new pads and flushed the brake fluid system completely. Brkaes never felt better, no dragging or anything, lovely jubbly. I thought this had even sorted the warped disc issue from Feb 2006.
+July 2013 @ 87k miles (just last weekend) - drive to screwfix with my old man so I can buy some jubilee clips to stop some exhaust heat shields rattling on my mothers car, 4 very sedate miles - no hard braking and probably didn't go above 45mph anywhere if I was lucky, park up in screwfix car park, and smell cooked brake. F N/S was stone cold and I could touch the caliper and disc etc, F O/S I couldn't even touch the wheel it was so hot. What was weird was that I didn't feel the car pull me to the right or anything. Anyway, so what I did was buy some allen keys and a G-clamp from screwfix as I was there, jacked the car up, took wheel off, undid caliper and pushed the piston back, waited for everything to cool down, and limped home using only the handbrake.
So after that, as I rewound the piston easy peasy, and I'd rebuilt them 2 years previously, I thought it unlikely it would be the calipers again, and in fairness when I rebuilt the calipers I didn't spot anything that looked bad. After lots of thinking/research and discussions, I decided it most likely to be the brake master cylinder, and that costs £267 from mazda. Anyway, I've taken the brake master cylinder apart, and can't find anything that looks odd.
Brake Master Cylinder by zippyonline, on Flickr
I then had another look at the master cylinder with a bit of a critical eye. Here are three pictures to show what I found:
Master Cylinder looking broadly from above, as if the reservoir was there.
P1170943 by zippyonline, on Flickr
Master cylinder reservoir joint closest to the pushrod/servo. Notice one hole which is a pinprick into the master cylinder, and the large hole which is located on the shoulder where the rubber seal/join bushing seals the feed from the reservoir.
P1170941 by zippyonline, on Flickr
And here is the master cylinder reservoir joint furthest from the pushrod/servo. Notice one hole, not on the shoulder of where the rubber seal is.
P1170940 by zippyonline, on Flickr
From what I understand (having just learnt in more detail off the tinterweb how a brake master cylinder works), the small pinprick hole is the fluid intake and return port which feeds off to the callipers, and the larger hole is the equalisation port behind the piston seal in the brake master cylinder so a vacuum is not caused. SO missing a hole on one of the circuits sounds like a possible cause of my sticky brake - but having not seen any other brake master cylinders apart, I'm not 100% certain and don't know about design variations and my particular car.
Given the history of the car from new and the constantly recurring F O/S sticky brake, I have a sneaking suspicion that this may be a manufacturing fault and the cause of my problems. I don't know which way round the brakes feed and it's not the easiest thing to follow round the car given it goes through the ABS module, but i'm guessing each piston on the master cylinder feed brakes diagonally opposite corners rather than front and rear or Left and Right as that's the norm as far as I'm aware.
So any advice gratefully received. If anyone has a master cylinder or taken one apart to compare, I'd really appreciate that too.
Thankyou very much.
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