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Post by smiley on Apr 29, 2022 17:43:21 GMT
Hey all.
I have an issue with an NB front brake sticking on and dragging. Caliper is approx a year old. The issue is the front left.
I have fitted new flexible pipes.
So when trying to rewind back the piston, it is extremely difficult. Releasing the brake bleed nipple fixes this and allows the piston to retract easily.
So it would appear that pressure is building to the caliper but not releasing back to the master cylinder. Hard lines look ok.
Checked the bias valve wasn't blocked, it appears OK and just seems to be a straight through system with nothing getting in the way, ie with the bottom pipe disconnected.
So my thoughts are the master cylinder. There does appear to be a slow brake fluid drop over time when using the car but have been unable to find the leak.
Is there something in the master cylinder that would stop brake fluid returning to allow me to narrow down the issue?
Thanks for any help or insights
Just for clarity, it's a non abs model.
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Post by atlex on Apr 30, 2022 12:57:49 GMT
it can't be the MC because the MC would cause either both front or both rear brakes to have the same problem.
I'd try a different calliper. they're not *that* expensive. ping autolink ?
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Post by smiley on Apr 30, 2022 14:58:48 GMT
it can't be the MC because the MC would cause either both front or both rear brakes to have the same problem. I'd try a different calliper. they're not *that* expensive. ping autolink ? The cylinder returns fine once the bleed valve is loosened so if it was a caliper issue, wouldn't the issue be there whether hydraulic pressure was on or off? |
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Post by warpspeed on Apr 30, 2022 21:41:15 GMT
It does sound like a sticky caliper. They can fill with grit and mud and that can jam the piston.
Probably easier to replace the whole caliper, although it would be possible to dismantled and thoroughly clean the existing one.
Its pretty normal when you bleed the brakes after some time, the very first bit of fluid that comes out of the bleed nipple can be pretty dirty.
As the brake pads slowly wear, the pistons end up further down the caliper bores, and the fluid level in the master cylinder very slowly falls over time. Its not a leak, its perfectly normal.
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Post by dadbif on May 1, 2022 7:04:20 GMT
Do you have a problem? It’s always easier to wind back a piston with the bleed screw open.
Wind your piston back, replace your pads, pump your pedal to reseat your pads and then see is your caliper still sticks.
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Post by smiley on May 1, 2022 19:56:53 GMT
Do you have a problem? It’s always easier to wind back a piston with the bleed screw open. Wind your piston back, replace your pads, pump your pedal to reseat your pads and then see is your caliper still sticks. The brakes are sticking on the passenger/left hand front wheel side. Changed the pads, cleaned everything up and lubricated everything. Took it for a spin and it's still sticking. For example, when I went to collect the new pads from the shop, the wheel was dragging on gravel as the wheel was locked up completely so had to release the pressure there at the shop and drive home carefully |
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Post by smiley on May 1, 2022 19:59:55 GMT
It does sound like a sticky caliper. They can fill with grit and mud and that can jam the piston. Probably easier to replace the whole caliper, although it would be possible to dismantled and thoroughly clean the existing one. Its pretty normal when you bleed the brakes after some time, the very first bit of fluid that comes out of the bleed nipple can be pretty dirty. As the brake pads slowly wear, the pistons end up further down the caliper bores, and the fluid level in the master cylinder very slowly falls over time. Its not a leak, its perfectly normal. I have to keep topping up the level as the warning light comes on every now and again. Maybe every 3 months. Caliper approx a year old. Everything is free and clean. Piston will not go back unless I release the bleed screw. It should go back with some force naturally. I had g clamp as tight as I could do it and it wasn't moving the piston back |
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Post by dickie on May 1, 2022 20:42:42 GMT
Check the condition of the flexible hose, look for kinks etc.
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Post by smiley on May 1, 2022 21:06:07 GMT
Check the condition of the flexible hose, look for kinks etc. Flexible hose is new, fitted to try and solve the issue |
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Post by Zed. on May 1, 2022 22:04:27 GMT
Check the condition of the flexible hose, look for kinks etc. Flexible hose is new, fitted to try and solve the issue I'm also drrawn to the pipework, have seen new hose-ends undrilled and rubber pipes damaged internally so they act as 'one-way' valves  if it has stainless braided hoses, DO NOT believe they are in perfect condition just because they look good - the inner ptfe pipe can be in terrible condition but hidden  also, braided hoses can be great 'earth-straps' so be carefull around elastic-trickery  Rich. |
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Post by atlex on May 2, 2022 9:48:34 GMT
100% ZED - if the piston also releases if you remove the feed line, it's the line what is stuffed. pinched into becoming a one way valve.
Just because a calliper is 'new' doesn't mean it's good. QA isn't what it was.
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Post by smiley on May 2, 2022 10:02:21 GMT
100% ZED - if the piston also releases if you remove the feed line, it's the line what is stuffed. pinched into becoming a one way valve. Just because a calliper is 'new' doesn't mean it's good. QA isn't what it was. Just to confirm, the brake was sticking and I expected the 1 way valve scenario so changed the rubber hoses to new rubber hoses. I will do a bit more digging today while bleeding the system. I thought I'd narrowed it down to something on the brake line side of things up to the master cylinder. If pressure is being held on at the caliper, I don't feel a new caliper will change that pressure, that's why I suspected the master cylinder or the bias valve but from what I see of the bias valve, the bit for the front left is just a straight through basically and I could blow through that fine with my mouth |
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Post by smiley on May 2, 2022 14:49:51 GMT
100% ZED - if the piston also releases if you remove the feed line, it's the line what is stuffed. pinched into becoming a one way valve. Just because a calliper is 'new' doesn't mean it's good. QA isn't what it was. So further analysis. I can't get the rear brakes to bleed. Pressure is going to the inlet of the bias valve for the rears but doesn't seem to be going out to the rear from the bias valve. Does the front left brake release some of that pressure to the rear through the proportioning valve? Could that be why the pressure isn't releasing? I took out the inner valve of the bias valve and had pressure to the rear so the issue is pointing to the bias valve |
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Post by atlex on May 2, 2022 20:08:31 GMT
Sounds like your brakes are going to get a DNR notice.
Any pressure in the system should be released back into the MC when you release the pedal. This is kind of why you need to close the bleeder when you take your foot off the pedal doing a bleed. air would get added in from the caliper as the MC changed direction, rather than fresh fluid getting sucked down.
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le sigh