RichieST

iTrader: (2)

Hi all

Mate at work put a new pair of rear calipers on a mk4 golf as they were both seized. The brakes were bled, bled some more, then bled again.

With the engine off, the brake pedal is nice and firm, however with the engine running, the brake pedal goes straight to the floor. As I said, the brakes have been bled so there is definately no air in the lines.

Any ideas before it goes up in smoke?


Rich

botters

iTrader: (2)

clamp off 1 brake pipe at a time then try the brakes if they go hard then the problem lies with the brake that is clamped, if they dont go hard at all with any of them clamped id say master cylinder

also try pressing the brake as hard as you can with engine off and pull the handbrake on a few times this will adjust the handbrake up on the back

dave_20

sounds simply but have tightened up the bleed nipples back up?
if not clamp all the hoses at each wheel and try it if its the same will be the sevo or a solid pipe.
hope this helps and sure some one with more skills and knowlage will help more

neil73

a mate is having the same problem, needs to have the abs pumps bled, needs some sort computer to work the valves while you bleed them, also master cylinder may need bleeding

google it mate and will explain more

RichieST

iTrader: (2)

Thanks for the info, will pass it on. My mate doing it is a pretty knowledgeable home mechanic but it's both got us stumped! Will let him know

phil_focus

i'd say master cylinder pesonally though do the brake line check first.

if the fluid has not been changed in a good number of years it will have absorbed water. the seals in the master cylinder can also absorb this water and swell. once bled with new fluid the new fluid draws out the water from the swolen seals causing them to deform and not seal resulting in a new master cylinder being needed.

also if the fluid hasnt been changed often enough the bit in the master cylinder where the seals dont touch (as under normal use they never move the max allowable amount) corodes and becomes rough so when you bleed the brakes using the pedal pumping method you end up tearing the seals to shreds resulting in needing a new master cylinder.

had this happen to my brothers renault megane as we did full service and renewed the brake fluid when he bought it and a few days later his foot hit the floor so we recon it was the swelling...and the fact its a renault!!!!

we changed it for a motor factors part and that improved it but still aint 100% but when doing the job there was no way to 100% gurantee no air would get into the abs module so i recon that needs bleeding. will have to be done at a garage though as has to be hooked upto a machine that cycles the solenoids inside. however, i'm hopeing that through time and getting the abs to kick in on grass and snow etc that it may bleed itself and then we will rebleed each corner. hopefully the motorfactor part isn't a different internal size causing excessive pedal travel but it was £80 as opposed to £140 odd from renault who would take over a week to order it in.

eoeumc

iTrader: (1)

I got this problem and as Rich170 said the pedal to the floor but mine is both when car is off and running.
I have also changed the rear cylinders, new fluid and put a new master cylinder in (mines a mk4 RS cabby). I am know thinking of getting the ABS pumps removed completely then try again. I also bought new Goodridge braided hoses to be fitted.

Is removing the pumps a good and easier option?

James @ M Developments.

iTrader: (2)

was it vaccum bled? or was the pedal pumped to bleed it?

if it was pumped id say the seals inside the master cylinder have turned.

thats why they should always be vaccum bled.

dojj

iTrader: (3)

Depending on what car it is I think that when the pedal has hitthe deck the seal inside has shat itself which is causing the problem. Some newer systems do need the abs stuff going on to bleed them properly if you let the master cylinder run dry

16imarty

think on them on the master clinder have bleed niples crack them off then re bleed system

rs-tuner

iTrader: (1)

There is 2 bleed nipples on the master cylinder. Has he bled these?

RichieST

iTrader: (2)

Thanks for all the help guys will pass on your suggestions! As far as I know it was bled by pumping through. Shall let him know

Daveysaff

iTrader: (9)

Master cylinder needs bleeding, ive just had the exact same problem on my golf.