brakes keep locking

[benniepak]

i have a 95 Subaru legacy bg5) and every time i brake it will lock up and it takes a bit of go pedal to make it move...i jack it up and sure enough the front left is locked and once iv freed it up the wheel spins freely but its only on the front left side.......have replaced caliper, bled the brakes....any ideas please

[Guest keltik]

Greased the sliders?

[log1call]

On a jack, jam the brakes on, try turning the wheel to check the brakes are staying on, release the bleed nipple and see if it frees the brakes. If it does free up when you release the brake pressure... change the hose.

[Guest boostin]

 keltik said:

Greased the sliders?

Yeah that, or a faulty brake hose. My money is on slides though.

[benniepak]

 boostin']

[quote name='keltik said:

Greased the sliders?

/quote]

Yeah that, or a faulty brake hose. My money is on slides though.

yeap done that already...took it in to a mate that works at winger subaru and he blasted it with some white spirit then greased it but still locking up

[log1call]

So have you tried loosening the bleed nipple?

[benniepak]

 log1call said:

So have you tried loosening the bleed nipple?

ok so do i push on the brakes to lock it up (which its already doing) the turn the wheel to see if it frees up when i break the nut??? if it does then replace the brake line??? is hat it?

coz i have found when pumping the brake pedal with the car on it hardens up then when i turn the car on and push it the pedal slowly hits the floor again but this happens still even after i bleed the system

[Guest]

There may be a problem with the master cylinder,

have the master cylinder rod in the vacuum boster checked for proper clearance,

the master cylinder has to be removed and there is a special tool to measure the clearance between the master cylinder pushrod and the master cylinder piston,

but in saying that i still have brake shudder and brke problems so i could be talking poo poo

[log1call]

That sounds like a different problem, but they may be related.

My suspicion is that your front brake hose has swollen up inside. When you push eight hundred pounds of pressure through it with the pedal it puts the brakes on, but there isn't enough pressure to return the fluid when you let the brakes off.

The other problem sounds like master cylinder seals. If you torn the engine off then push very very slowly and gently on the pedal you may find it goes to the floor, but, if you stamp on the pedal suddenly and keep a bit of pressure on the pedal it might stay hard. If it does do that it's because the cup seals splay out under pressure, especialy sudden pressure, but with a gentle push they slide down the cylinder letting the fluid creep past the worn seal.

The swollen hose is probably caused by contamination, and the same contamination may have buggered your master cylinder.

If the bleed nipple being loosened fixes the locked brakes, change the hose then try bleeding the system before condemming the master cylinder though.

[Guest boostin]

 benniepak']

[quote name='keltik said:

Greased the sliders?

/quote]

Yeah that, or a faulty brake hose. My money is on slides though.

yeap done that already...took it in to a mate that works at winger subaru and he blasted it with some white spirit then greased it but still locking up

I know this mate you're talking about, and I'm not entirely convinced he knows what he's doing. Lol ;D

[Guest]

 log1call said:

That sounds like a different problem, but they may be related.

My suspicion is that your front brake hose has swollen up inside. When you push eight hundred pounds of pressure through it with the pedal it puts the brakes on, but there isn't enough pressure to return the fluid when you let the brakes off.

The other problem sounds like master cylinder seals. If you torn the engine off then push very very slowly and gently on the pedal you may find it goes to the floor, but, if you stamp on the pedal suddenly and keep a bit of pressure on the pedal it might stay hard. If it does do that it's because the cup seals splay out under pressure, especialy sudden pressure, but with a gentle push they slide down the cylinder letting the fluid creep past the worn seal.

The swollen hose is probably caused by contamination, and the same contamination may have buggered your master cylinder.

If the bleed nipple being loosened fixes the locked brakes, change the hose then try bleeding the system before condemming the master cylinder though.

yup but what he has said the pedal will slowly move toward the floor. This is a sure sign the master cylinder is bad. A leaking master cylinder or one that sticks, is also a sign it is defective..Moisture maybe even the baddy here???

[Guest]

dont mea to hijack this post but i know a lil bit about brakes and i think I have found the source to my problemzzzz... this morning I noticed brake fluid leaking from the abs system driver’s side main unit... I hate looking under the bonnet of a Subaru man lol... as i said i know a lil bit about braks but abs mmmmm not much havnt read up on them befor...so can the ABS Pump and Motor Assembly b fixed in some way or just best to get another

[log1call]

I dont mean to question your claim that you "know a bit about brakes", if in fact it is a claim, not an admission, but...

The pedal going to the floor is not a sure sign the master cylinder is bad. Air in the system could cause that as could leaks.

The original problem was one front brake sticking on. As I understand it, from this thread, the pedal going to the floor has developed since he has worked on the brakes. Since it was only one front brake I think we can rule out master cylinder being the cause.

I think he needs to fix the original problem then address the new problem if it hasn't been cured in the process of fixing the first fault.

Jumping to conclusions, especially illogical conclusions, which involve replacing parts is stupid in my opinion. Just an opinion though.

[benniepak]

 log1call said:

I dont mean to question your claim that you "know a bit about brakes", if in fact it is a claim, not an admission, but...

The pedal going to the floor is not a sure sign the master cylinder is bad. Air in the system could cause that as could leaks.

The original problem was one front brake sticking on. As I understand it, from this thread, the pedal going to the floor has developed since he has worked on the brakes. Since it was only one front brake I think we can rule out master cylinder being the cause.

I think he needs to fix the original problem then address the new problem if it hasn't been cured in the process of fixing the first fault.

Jumping to conclusions, especially illogical conclusions, which involve replacing parts is stupid in my opinion. Just an opinion though.

OK guys this all started with a real bad wheel bearing but before that, brakes were fine all four corners... i then replaced the whole hub and shaft(front left) after bout 3-4 days later but made sure not to stress the brake liine(haning for the 3-4 days) and so after everything was put back together thats when the problem started. i just dont get why just that one side...if it was the master cylinder wont it affect all four brakes or not??? but the brake hose sound about right i shall try this step first b4 the master cylinder

[benniepak]

 boostin']

[quote name='keltik said:

Greased the sliders?

/quote]

Yeah that, or a faulty brake hose. My money is on slides though.

yeap done that already...took it in to a mate that works at winger subaru and he blasted it with some white spirit then greased it but still locking up

I know this mate you're talking about, and I'm not entirely convinced he knows what he's doing. Lol ;D

lmao he tells me he learns from the king (if not you, then maka) lmao

[Guest]

 log1call said:

I dont mean to question your claim that you "know a bit about brakes", if in fact it is a claim, not an admission, but...

The pedal going to the floor is not a sure sign the master cylinder is bad. Air in the system could cause that as could leaks.

The original problem was one front brake sticking on. As I understand it, from this thread, the pedal going to the floor has developed since he has worked on the brakes. Since it was only one front brake I think we can rule out master cylinder being the cause.

I think he needs to fix the original problem then address the new problem if it hasn't been cured in the process of fixing the first fault.

Jumping to conclusions, especially illogical conclusions, which involve replacing parts is stupid in my opinion. Just an opinion though.

lol i realy did mean a littel bit !Literally!, was going on what has happend to me is all my friend...and now he has stated the above yea ur rite...maybe ...care for a frindly wager of say 5buks? hoses that deteriorate and collapse inside to block the flow

. These then act like check valves, allowing passage of high pressure fluid from the master cylinder to the wheels, but restricting the low pressure return flow.

This commonly causes the lock up of one front wheel, or both rear wheels so i know hat you saying

[Guest keltik]

it takes a fair bit of fluid pressure to lock a wheel, so it seems illogical to me that the pressure would flow one way but be blocked from flowing back by a hose. Could an ABS unit fault cause something like this?

[Guest]

Hmmmm ABS sensor dont know anything about abs system as i have issues with it now :-[

[log1call]

Ok, the brake hose could have a flap of rubber loose inside it which may have been moved during a brake bleed and is now blocking it, or, there could be a bit of crud stuck in the return port of the master cylinder, once again caused by the bleeding. If it's a blocked return hole in the master cylinder then the right rear and left front should both be sticking on,(I think, maybe, depends on the system).

Easiest thing though, is to loosen the left front bleed nipple and see if it releases the brakes. If it does take the hose off and try blowing through it. Have a beer handy to remove the brake fluid from the mouth.

[log1call]

As you say Keltic, it takes a bit of pressure to lock the brakes, hundreds of pounds of pressure in fact, and there is nothing but a bit of distorted rubber to force it back the other way again. I think it's imminently logical... but I would!

Apart from the theory involved, I have seen it heaps of times in my career as a mechanic.

And, if the theory and the experiance isn't enough to convince you it's a good line of investigation to start with... It's the simplest thing to try and it doesn't cost anything but a few minutes of time and a bit of brake fluid.

[log1call]

Ok GF8M8, I have put a couple of abs articles here... http://cid-4ca3c3459aaa7f7f.skydrive.live.com/browse.aspx/.Public?uc=2 Ones about the systems used on subarus and the other is about bleeding them. Download then and have a read.

[Guest]

 log1call said:

Ok GF8M8, I have put a couple of abs articles here... http://cid-4ca3c3459aaa7f7f.skydrive.live.com/browse.aspx/.Public?uc=2 Ones about the systems used on subarus and the other is about bleeding them. Download then and have a read.

you are the man ;D thank you very much..as i love to read and learn this will come in handy for sure.. awsome

[log1call]

Good for you. Knowledge is power.

[Guest]

that book7 is awsome...the abs stuff is just what i needed to bret

[log1call]

Benniepak... What have you found?