Rear brakes not working.

[sean mehigan]

Hi everyone, replaced rear left corroded brake piping all the way to the abs pump. I noticed when the brake pedal is pressed firmly, no brake fluid at highish pressure will exit the rear caliper bleed screw. I do know how to bleed the air from brake systems. When the foot pedal is pressed firmly, both rear wheels can be rotated freely by hand. Does the abs pump need a diagnostic reset. There are no fault lights on the dash.

 

[onefortheroad]

Crack each nipple in turn , keep the resovoir full and let gravity do its thing .

 

[sean mehigan]

Crack each nipple in turn , keep the resovoir full and let gravity do its thing .

Thanks, I will be shocked if there is still air in it.

 

[LostKiwi]

On some vehicles you need to operate the ABS pump using diagnostics to bleed them properly.

 

[sean mehigan]

Thanks, I will keep that in mind Kiwi.

 

[sean mehigan]

Thanks, I will keep that in mind Kiwi.

Well, interesting news here. With the car on a lift and the brake pedal is applied, both rear wheels can still rotate. No warning on the dash while driving. No diagnostic errors or codes. The garage now believe it's the master cylinder have failed (no pressure to the back wheels) New master cylinder on order.

 

[davidsl500]

When bleeding the brakes did you press the pedal flat to the floor because that will move the master cylinder piston past the wear lip and damage one of the seals.

 

[sean mehigan]

I am aware that there was slackness for the first 2 inches or so and had resistance after that. I cannot be sure if the pedal was pressed to the metal or not. Thanks anyway.

 

[LostKiwi]

Not sure on yours but on some cars there is a brake proportioning valve fitted in the rear line. These can operate from a linkage to the rear suspension arms or rear anti roll bar. If the linkage breaks the rear brakes get shut off, the idea being that if the rear suspension lifts then it has less ability to grip the road.

 

[Wighty]

When bleeding the brakes did you press the pedal flat to the floor because that will move the master cylinder piston past the wear lip and damage one of the seals.

I’ve never heard that one before buddy ?

 

[sean mehigan]

Not sure on yours but on some cars there is a brake proportioning valve fitted in the rear line. These can operate from a linkage to the rear suspension arms or rear anti roll bar. If the linkage breaks the rear brakes get shut off, the idea being that if the rear suspension lifts then it has less ability to grip the road.

I remember my old Peugeot 305 van having that system in the back. I don't think it's in the w204 saloon though.

 

[davidsl500]

I’ve never heard that one before buddy ?

It's a common enough issue Wighty. It's been discussed before. Always best to put a block of wood under the brake pedal when bleeding the brakes the "old fashioned way" to stop the pistons hitting the wear lip and potentially flipping the cylinder seals..

 

[Wighty]

It's a common enough issue Wighty. It's been discussed before. Always best to put a block of wood under the brake pedal when bleeding the brakes the "old fashioned way" to stop the pistons hitting the wear lip and potentially flipping the cylinder seals..

Say no more , bleeding procedures have just changed

 

[EmilysDad]

Say no more , bleeding procedures have just changed

You're not alone Wighty. I've heard of, but never experienced, seals flipping during the old up/down/up/down method of brake bleeding, but never heard of flipping seal by pressing the pedal to the floor ....

 

[davidsl500]

As well as the lip, the normally unswept areas of the bore can get rusty from the water absorbed by the brake fluid which can help to score/rip the seal. Unless you are fitting a new master cylinder its best not to let the pedal go to the floor.

 

[Kev555]

Yip i always practised that when bleeding. found if you go to far and damage the seal you will always have a soft pedal or one that goes to the floor as fluid pushes past the damaged seal while braking. Most of the time you will get away with pushing the pedal to the floor especially if youve somebody inexperienced pumping the brakes like the wife or one of the kids while your bleeding

 

[Wighty]

Just thought I would see what my Haynes manual says on the brake pedal to the floor issue , there is no warning at all , just says when applying pressure follow the pedal down the floor if necessary

 

[Kev555]

Ever notice when Haynes were making a manual it was on a new or nearly new car? Not the 10-20 year old headaches we have

 

[LostKiwi]

Ever notice when Haynes were making a manual it was on a new or nearly new car? Not the 10-20 year old headaches we have

That's why they say "gently ease the part out" we know that it will really be "beat the part senseless, mangle it so it's unrecognisable, find gas axe and melt it out".

 

[Blobcat]

That's why they say "gently ease the part out" we know that it will really be "beat the part senseless, mangle it so it's unrecognisable, find gas axe and melt it out".

'Reassembly is a reversal of dismantling'...