# no pedal when the engine is running



## Undertaker4 (Sep 14, 2010)

so ive been doing some looking around in the brakes tech forum, and im not really seeing anything that can be related to what is wrong with my car, i have a 01 GTI VR6, i recently took off the rear caliper to see if the piston was frozen, and its not, so i then decided to shove the cylinder back into the caliper, it wouldnt retract, only spin, so i took the e-brake cable off, and the brakes hose, the cylinder then went back in, so i did the same process on the other rear caliper. after they were both installed i then pumped the brakes to push the cylinder up against them pads, started the engine to see if they would work, they dont so i bleed all 4 brakes in proper order, still no pedal when the engine starts up, but with the engine off i have a very firm pedal, just not with it running. now ive made sure there is no air in my lines, my fluid is topped off, all air hoses are connected properly, there are no leaks from any of the hoses. thanks in advance for the help


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## Undertaker4 (Sep 14, 2010)

bump anyone? this is still a problem


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## germancarnut51 (Mar 23, 2008)

If you pushed the pistons back into the rear calipers without using a piston retracting tool (which rotates and presses the pistons at the same time to retract them into the calipers), you have destroyed the self adjusting mechanisms in the rear brake calipers. Since the rear brakes would no-longer self-adjust to close the rotor to brake pad gap, the rear brakes would no longer function, and you would end up with no brakes at all. The only cure would be replacement of both rear brake calipers.

If this is not what you did, post another message explaining exactly what you did, and maybe someone can help you.


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## Undertaker4 (Sep 14, 2010)

so i got a new Master Cylinder, bench bled it, then installed the MC tightened up all the bolts and fittings, then bleed all 4 wheels starting with the one furthest from the MC, started it up, pumped the pedal, still no sufficient pedal, looked underneath the car while pumping the brakes, no sign of leaking fluid, and advice would be greatly appreciated


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## GTijoejoe (Oct 6, 2001)

germancarnut51 said:


> If you pushed the pistons back into the rear calipers without using a piston retracting tool (which rotates and presses the pistons at the same time to retract them into the calipers), you have destroyed the self adjusting mechanisms in the rear brake calipers. Since the rear brakes would no-longer self-adjust to close the rotor to brake pad gap, the rear brakes would no longer function, and you would end up with no brakes at all. The only cure would be replacement of both rear brake calipers.
> 
> If this is not what you did, post another message explaining exactly what you did, and maybe someone can help you.


If this were true, than the pistons would still be frozen and the pedal would be rock hard from no fluid consumption of the RR calipers.
Normally the self adjusting mechanism is a power screw, easily scews out when fluid pressure builds and binds when trying to push it in without scewing.

To OP, you may need your modulator circulated and bleed with the rest of the system....


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## cuppie (May 4, 2005)

Seconded to that.
Since you opened up the top end of the brake system, you'll never get the ABS hydro unit bled by 'normal' means.
You'll need to either take the car to the dealer, or find a shop or friend who has a VAG-COM to bleed the brakes properly.

Before you do that, though, make sure that the slider pins on all of the calipers still, well, slide. A siezed slider pin will also cause a 'low' brake pedal (I say this because I've actually seen and fixed it.)
Once those are sorted (if needed), _then_ go get your brakes re-bled.


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## germancarnut51 (Mar 23, 2008)

Are your paking brake cables still good? The outer rubber sheath cracks and lets moisture in, which results in the cable seizing to the metal inner housing of the cable.

You can check the cable by going under the back of the car to check the position of the parking brake levers under the car (block up the wheels on the ground) with the parking brake engaged, and then with the parkimng brake off to see if both parking brake levers are moving.

If the parking brake levers are not moving, then there's a problem with the cables. The parking brake mechanism is used to adjust the rear brake pad clearance. If the parking brakes are working, then the rear brake pad clearance will be excessive, and both the front and rear brakes will not work correctly.

The parking brake mechanism (and self adjusting rear brake mechanism can be damaged by forcing the pistons into the calipers) which is why I asked how/what you used to retract the pistons into the calipers.


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