[Matt_keys]

So I've had this golf for. Over a year and it's sat on the drive while I've been replacing stuff sorting bits out and building the engine up etc.

I took it out and I had barely any braking force. And the pedal slowly pushes to the bottom of you push and hold

So thinking it was the master cylinder I've changed the mc I've vacuum and pressure bled the system, ran over a litre of brake fluid out. The old fluid was green so thought this is Likley the issue maybe full of Mosture

The pedal felt better but did the same thing

So got vcds, run the abs procedure about 6 times and was getting some decent air bubbles out the front left so kept going untill there was none.
The pedal then felt really good with the engine of and I don't think there was any creep

As soon as I've turnt the car on the pedal can be pushed to the floor with little resistance. Like I've got all the brake bleed nipples open

Ive checked for leaks and had some one press and hold the brake pedal (the other day before vcds pump bleed) and there's no flexis bulging etc

No leaks can be seen over night/days and the brake fluid doesn't drop

So I've made it worse which is crazy

Looking at the output tests I get these readings... I have no idea what the values are meant to be.

What can I do next? Is it possible the abs pump is screwed? Or maybe still got air?

 

[adam-]

Have you bled the master too? Run a litre of fluid through each caliper. It will go. Bleeding sequence doens't matter.

 

[Matt_keys]

Have you bled the master too? Run a litre of fluid through each caliper. It will go. Bleeding sequence doens't matter.

Yea done the master... I'll redo each corner again
Once done should I run the abs bleed again?

Is it possible the abs pump is bad and has a stuck valve letting fluid by?

 

[adam-]

ABS bleed doesn't do much IMO. If you have a poor pedal, just keep bleeding. Also nope, you want fluid to get by. If you can't get fluid out the caliper you have an ABS issue, but you don't.

 

[Matt_keys]

OK... After wasting another 4 litres of brake fluid... It's still the same...

So changed the abs pump for a known working unit I then bled another litre brake fluid through each caliper

then carried out the ABS pump procedure a few times and got air out

so went to output test and run the pump on each corner. I reckon another half litre on each corner while topping up the master cylinder

again feels solid with the car off when you turn the car on the pedel falls to the floor like you are pressing the clutch

So the only things left are the booster....

Help!


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[adam-]

Master cylinder is the only thing left. Booster doesn't affect it. You're trying to move an incompressible fluid, so if it compresses, there is air or the fluid is passing the seals in the master.

 

[Matt_keys]

Master cylinder is the only thing left. Booster doesn't affect it. You're trying to move an incompressible fluid, so if it compresses, there is air or the fluid is passing the seals in the master.

Yea I know... But where the hell is the air gonna be because having used all that fluid and having used a pressure bleeder.

The master cylinder is new so unless I've fucked the master cylinder in the process?



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[adam-]

You don't need to bin the fluid btw. Just reuse it.

Unlikely, but could be dead out the box. If the seals were bad it would pass even with the engine off though. IMO it's just air. You could take your old ABS pump and fit bleed nipples onto the outlets, bleed it through and prove the master. Bit of work though.

 

[Matt_keys]

Yea I'll give it another shot next weekend. Was considering buying another master cylinder

Otherwise might have to just get a garage to have a go as it's getting annoying

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[jackrome245]

Yes


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[Dave S]

Yea I'll give it another shot next weekend. Was considering buying another master cylinder

Otherwise might have to just get a garage to have a go as it's getting annoying

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Hi Matt, did you fix the "pedal OK with engine off/ going to the floor with engine running" problem?

 

[Dave S]

I've now managed to get the brakes bled to give a reasonable pedal. After ABS module bleeding with VCDS, I had a good pedal with engine off, but when the engine was running it went to the floor. I then tried bleeding with the engine running and me pushing the pedal. I attached my Gunson Eezi-bleed to the master cylinder, and ran about 2 litres of fluid through each calliper. Pedal feel is now OK. Hope this helps.

 

[adam-]

Bleed the master. Sequence doesn't matter. Bled mine last weekend, had it sat empty for 2 years. Bled in whatever sequence I wanted, just walked round it. No issues with pedal.

 

[adam-]

*no VCDS used either.