BMW 320i front brakes locked up

[eejay56]

1979 320i. What would cause the front brakes to not be releasing.

 

[Steve]

Is it both sides, or just the one?

My first thought is that it might well be a flexible barke line that has collapsed internally, not allowing the hydraulic pressure to release.

 

[eejay56]

Both sides just the front. Flexible brake lines seem OK.

 

[jessebogan]

Frozen pistons in the front calipers, Master cylinder pushrod mal-adjusted, master cylinder failure,Heavy corrosion in calipers "holding" the pads against the rotors, rusty rotors. Thats about all that comes to mind.

 

[eejay56]

Thanks.I going to order a master cylinder rebuild kit and see if that does it.

 

[Bugeye58]

EJ, The front hoses may look OK from the outside, but they deteriorate from within. Then they act like check valves. There is enough pressure from the M/C to actuate the brakes, but not enough residual pressure to allow the pistons to retract fully.
Jeff

 

[Steve]

I was thinking along those lines. It's an older car, so maybe?

 

[mikespain]

when they are stuck on-try cracking the bleed nipple on the caliper-if the brake releases then the problem is before the caliper,press the brake gain to lock them and crack the union above the brake hose-if it is still stuck on then the problem is the brake hose .don't forget to have something to catch the fluid that comes out.Again if it releases the problem is before that point.then probably the master cylinder .

 

[Eric]

I'm not familiar with 320 brakes, but on many modern cars (that I consider the 320 a modern car betrays my age....) with single piston calipers, the slide mechanism needs lubrication, especially if it is somewhat worn and allows the caliper to cock sideways a little.

On my Miata, I need to lube the sliders (esp. the rears) yearly, as a maintainance item, or they'll stick.