Rear brake locked
v8james - 14/8/09 at 11:13 AM
I am running standard Sierra brakes, callipers and disks up front and drums on the back.
I have now fitted a bias pedal box with two cylinders 0.625 on the front and 0.75 on the back.
All the lines have been bled, fronts are working great but the rear offside drum is locking solid and will only release the wheel when I open the bled
nipple.
Thought there might be air in the rear line, but surely both drums would lock until the pressure was released.
Does anyone have any ideas?
James
Mr Whippy - 14/8/09 at 11:17 AM
yip, the hose has aged and collapsed inside effectively making a one way valve
[Edited on 14/8/09 by Mr Whippy]
adithorp - 14/8/09 at 11:27 AM
If it's just one side then probably as above. No play in the master cylinder push rod would also do it but probably both sides.
adrian
v8james - 14/8/09 at 11:30 AM
Good idea, didn’t think of that.
Will replace both hoses over the weekend.
James
britishtrident - 14/8/09 at 01:32 PM
Master cylinder push rods not allowing the master cyilnder piston to fully return. --- yes I know only one caliper apears to be affected and it
appears to go against all hydraulic theory but that is what it is.
Hoses collapsing is an old wifes tale it just never happens ------
[Edited on 14/8/09 by britishtrident]
[Edited on 14/8/09 by britishtrident]
v8james - 14/8/09 at 01:42 PM
The cylinder is returning fully and pushrod is loose when brake is not applied, that’s the first thing I checked.
James
Mr Whippy - 14/8/09 at 02:26 PM
quote:
Originally posted by britishtrident
Hoses collapsing is an old wifes tale it just never happens ------
actually I had 4 that came off my beachbuggy that had collapsed and were also locking the brakes completely, couldn't even blow through them.
Were very old though, about 15 years at least and had been bent while in storage.
britishtrident - 14/8/09 at 02:36 PM
quote:
Originally posted by v8james
The cylinder is returning fully and pushrod is loose when brake is not applied, that’s the first thing I checked.
James
It is actually very difficult to check -- it just needs the washer that retains the pushrod in the cylinder to be the wrong washer or not beveled
correctly --- not going fully back by less than 1 mm is enough.
rusty nuts - 14/8/09 at 06:35 PM
quote:
Originally posted by britishtrident
Hoses collapsing is an old wifes tale it just never happens ------
Have to disagree , it does happen I've had several Ford Escorts in the last 5 years or so that have had a front brake locked on due to a faulty
hose.
nz_climber - 14/8/09 at 08:53 PM
Seen it on an old VW combi van, both rear hoses had collasped, no fluid could go in any direction!
x_flow57 - 14/8/09 at 09:28 PM
Sorry but it does, I've seen it on more than one occasion, fluid passes under pedal pressure but fails to return and causes brakes to stay on.
quote:
Hoses collapsing is an old wifes tale it just never happens ------
Nick
adithorp - 14/8/09 at 10:01 PM
I see collapsed brake hoses regularly.
adrian
ps. make the most of it boys; He's not wrong very often. 
In fact before this I'd have said "It never happens"
v8james - 15/8/09 at 08:41 AM
Replaced hoses, now works perfectly.
Seems the master cylinder was returning fully after all.
Thanks for the help Mr Whippy.
James
britishtrident - 15/8/09 at 03:49 PM
Cured ? -- we shall see.