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Discussion Starter #1
Hi 46 fanatics,
I just got my car back from the mechanic and my rear left brakes keep locking and not releasing unless you leave the pedal for around 30 minutes , we changed calipers and abs sensors, is there anyone with experience in fixing this?




BTW its a 2000 E46 330ci.
 

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I'd be looking at the rubber hose. They swell internally with age and can cause your problem. What's your mileage? If so l'd be doing them all.
 

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...or you have air in your calipers still, so depending on how you bled them, might be worth another shot.

One 'trick' that might work, if you haven't done so yet, OP. With the car off, pump up the brake pedal until it's firm...then start the car. I believe this builds up pressure that 'perhaps' your caliper isn't getting.

Also, if the hoses are old, do replace as suggested...but use flare wrenches to break the seal...it is a tight fitting!
 

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...or you have air in your calipers still, so depending on how you bled them, might be worth another shot.

One 'trick' that might work, if you haven't done so yet, OP. With the car off, pump up the brake pedal until it's firm...then start the car. I believe this builds up pressure that 'perhaps' your caliper isn't getting.

Also, if the hoses are old, do replace as suggested...but use flare wrenches to break the seal...it is a tight fitting!
Out of curiosity, how would air in the system keep pressure on the caliper?
Yes, proper tools are important to avoid damaging the metal pipes unless your mechanic is doing it.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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Likely the hose.
Could also be internal to the DSC unit.
 

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Out of curiosity, how would air in the system keep pressure on the caliper?
Yes, proper tools are important to avoid damaging the metal pipes unless your mechanic is doing it.
That's a good question! Probably not, I guess. I was thinking that if it never had enough pressure it might not have enough to pull off the rotor. Early in the a.m. and it's windy. :)
 

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Image1605628618.615433.jpg


My project last week: SS lines. It was easier than I thought it would be. ShopLife has a good YouTube DIY video that I followed.

Not very expensive and it made a difference since everything else has been changed: booster, master cylinder, pads and rotors.

Good luck!

Tools I used:

flare wrenches (9 and 14 mm I think)
Motiv brake bleeder pump and catch bottle
About 1/2 liter new brake fluid
The usual jack and stand.
Screw driver and mallet to remove retaining clip that secures the brake line in the middle. I think 50skid shows how to wack that clip in order to remove it in his brake video. Hit it with some penetrating fluid because mine was stuck pretty good. However on reassembly the clip is really loose. Not sure if they’re one-time-use only?

Some penetrating fluid and brake cleaner to clean up the fitting before removal.

Pan to catch dripping brake fluid. And rags.

I saw a vid of a silicone cap that you can put on the end of the brake line to keep the fluid from leaking out. Sorry but I don’t know where to get them. Maybe someone can chime in. Although as long as you have a catch pan it doesn’t really leak all that much fluid.

Parts:

Set of new brake lines

Symptoms:

Ballooning feeling when you step hard on the brakes. I.e. the brakes take a 1/4 second extra to fully engage.

HTH!
 

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SS lines. It was easier than I thought it would be. ShopLife has a good YouTube DIY video that I followed.

Not very expensive
looks clean. never changed anything on my brake system except one dsc pressure sensor, rotor (once) and pads, pad wear sensors, fluid flushes...might do this. without us thread jacking (maybe just edit your post(#7), what exactly were replaced on this? no special tools, just regular wrenches to undo, reassemble?
 

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looks clean. never changed anything on my brake system except one dsc pressure sensor, rotor (once) and pads, pad wear sensors, fluid flushes...might do this. without us thread jacking (maybe just edit your post(#7), what exactly were replaced on this? no special tools, just regular wrenches to undo, reassemble?
The suggestion was that if you are doing brake lines, steel or rubber, you really need a set of flare wrenches, or crows feet in a pinch, to deal with the fittings. And PB blaster I expect. You do not want to compromise the fitting on a pipe that goes straight to the front.
If you have a clutch, might as well do that one too.
 

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Discussion Starter #10
I'd be looking at the rubber hose. They swell internally with age and can cause your problem. What's your mileage? If so l'd be doing them all.
My milleage is 215000km (133594.8miles), I havent changed the hoses, I will try replacing them today and get back to you.
 

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...or you have air in your calipers still, so depending on how you bled them, might be worth another shot.

One 'trick' that might work, if you haven't done so yet, OP. With the car off, pump up the brake pedal until it's firm...then start the car. I believe this builds up pressure that 'perhaps' your caliper isn't getting.

Also, if the hoses are old, do replace as suggested...but use flare wrenches to break the seal...it is a tight fitting!
When the caliper locks up the pedal remains hard, even if I start up the car it still remains pressurised, the idea of air build up makes sense, I will double check with my mechanic if he bled the system fully
 

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Discussion Starter #12
View attachment 915384

My project last week: SS lines. It was easier than I thought it would be. ShopLife has a good YouTube DIY video that I followed.

Not very expensive and it made a difference since everything else has been changed: booster, master cylinder, pads and rotors.

Good luck!

Tools I used:

flare wrenches (9 and 14 mm I think)
Motiv brake bleeder pump and catch bottle
About 1/2 liter new brake fluid
The usual jack and stand.
Screw driver and mallet to remove retaining clip that secures the brake line in the middle. I think 50skid shows how to wack that clip in order to remove it in his brake video. Hit it with some penetrating fluid because mine was stuck pretty good. However on reassembly the clip is really loose. Not sure if they’re one-time-use only?

Some penetrating fluid and brake cleaner to clean up the fitting before removal.

Pan to catch dripping brake fluid. And rags.

I saw a vid of a silicone cap that you can put on the end of the brake line to keep the fluid from leaking out. Sorry but I don’t know where to get them. Maybe someone can chime in. Although as long as you have a catch pan it doesn’t really leak all that much fluid.

Parts:

Set of new brake lines

Symptoms:

Ballooning feeling when you step hard on the brakes. I.e. the brakes take a 1/4 second extra to fully engage.

HTH!
Thanks for this guide, I will try a DIY, I thought changing the hoses would be a job for the pros but doesn't look that difficult.
 

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Provided some caveats are met: Master cyl is in good condition, pedal/rod through booster is not hanging up and the orifices/valves in the ABS/DSC pump are free. The pistons will retract ever so slightly after the pedal is released.

Impediments to normal retraction are; restricted whip hose or scored pistons/with bad seals letting the piston not pull off.

Theoretically any air in the system would provide less resistance to a piston retraction for a given circuit (4 of them) owing to the superior compress-ability of air over hydraulic (Dot 4) fluid.
 

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When the caliper locks up the pedal remains hard, even if I start up the car it still remains pressurised, the idea of air build up makes sense, I will double check with my mechanic if he bled the system fully
I thought changing the hoses would be a job for the pros but doesn't look that difficult.
I don't think the rubber hose is the problem, as this normally only causing a brake dragging issue and this should not cause the pedal hard due to pressurized system. It sounds to me the issue is at the master cylinder: the pedal free travel is not adjusted correctly and causing the master piston not fully retract to clear the bleeding hole (which allows the pressurized fluid to return back to reservoir ).
 

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[QUOTE="MrMCar, post: 18854725,

Theoretically any air in the system would provide less resistance to a piston retraction for a given circuit (4 of them) owing to the superior compress-ability of air over hydraulic (Dot 4) fluid.
[/QUOTE]
So are you saying air in the system could cause the calipers to stay locked? Or not? Maybe I need coffee.
To OP's issue, the system will have to bled again if you change the hoses.
 

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I don't think the rubber hose is the problem, as this normally only causing a brake dragging issue and this should not cause the pedal hard due to pressurized system. It sounds to me the issue is at the master cylinder: the pedal free travel is not adjusted correctly and causing the master piston not fully retract to clear the bleeding hole (which allows the pressurized fluid to return back to reservoir ).
How would it get out of adjustment?
 

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[QUOTE="MrMCar, post: 18854725,

Theoretically any air in the system would provide less resistance to a piston retraction for a given circuit (4 of them) owing to the superior compress-ability of air over hydraulic (Dot 4) fluid.
So are you saying air in the system could cause the calipers to stay locked? Or not? Maybe I need coffee.
To OP's issue, the system will have to bled again if you change the hoses.
[/QUOTE]
NOT
 
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