aw11 brake pedal goes to the floor sometimes

[30psi 4agte]

you need to get a couple of clamps and clamp of variou rubber brake hoses . use vice grips or you can buy brake clamps ( they fairly cheap!!)

what you do is clamp off the back brakes and test the pedal. if the pedal is harder you no you still have air in the back (or there is a prob with back ) do mthe same for the fronts.

[myne]

Hold your foot firmly on the brakes while stationary. If the pedal slowly sinks, your mastercylinder is rooted.

[KLR16V]

Hold your foot firmly on the brakes while stationary. If the pedal slowly sinks, your mastercylinder is rooted.

yeah thats what sort of happends... but only occasionally

mainly when im creeping at traffic lights

[30psi 4agte]

Hold your foot firmly on the brakes while stationary. If the pedal slowly sinks, your mastercylinder is rooted.

or there is a leak somewhere !!!!!!!!!!!!!!!!!!!!!!!!!!!!
A caliper or brake line could be leaking uder pressure and causing the pedal to sink

[feral4mr2]

my pedal slowly sunk to the floor when waiting in traffic or applying the brake slowly.
after i pulled the master cylinder out seen the pitts on the bottom of the bore. re-sleeved as i mentioned above and i put in some new rubbers and it's all good.

you would see a brake fluid leak prity easily.

[4agte]

it has a habbit of corroding most things it touches too

[Bored?]

If a caliper had a leak it would probably result in fluid loss.
Given that you are not loosing any fluid, it is probably the master cylinder.
Replacing the master cylinder would be the next thing to try.

That said, a visual inspection of the brakes and lines for fluid won't take long.

[KLR16V]

yeah there is no fluid leaks anywhere. i must check out the MC soon.

[YelloRolla]

Hold your foot firmly on the brakes while stationary. If the pedal slowly sinks, your mastercylinder is rooted.

Good one for offering a test/solution.

I will attempt to help clarify it.

If you hold the brake pedal hard, and it doesn't go to the floor, THEN you back off and push it gently and it DOES go to the floor, then this is certainly the rooted MC diagnosis.

The reason that holding it hard will stop it going to the floor is the fluid pressure inside the "cup shaped seals" will actually keep them pressed to the cylinder wall. Holding it gently has the opposite effect, allowing the fluid to "bleed down".

[KLR16V]

I will attempt to help clarify it.

If you hold the brake pedal hard, and it doesn't go to the floor, THEN you back off and push it gently and it DOES go to the floor, then this is certainly the rooted MC diagnosis.

yep tried this and after pushing the pedal hard, when i pushed it gently it went to the floor.

so yeah my mc must be rooted

probably explains why my brakes go to the floor when im in traffic. i brake hard to slow down, then when im only gently using the brake while in traffic the dont work.


thanks yellorolla

[feral4mr2]

unless you want to pay a arm and a leg for a new one (providing you can find one), send your master cylinder away to get re-sleeved with a stainless steel sleeve (will never pitt/corode again).
when i sent mine away to be re-sleeved i couldnt source a seal kit (i worked in spare part, didnt try genuine though), i found one in the PBR book that was basicaly the same from a hi-ace. cannot remember the part number, but if your go through a spare parts store, get them to look in the PBR book at hi-aces around the same era.