Brake issues- soft pedal ***updated with video***

[bigwinn]

Hi all

So a new issue with the project to sort

The brake pedal is very soft. Will go to the floor with minimal resistance. However with a few pumps it tightens up to how you’d expect.

New fluid and full bleed including ABS bleed
New hoses
No leaks
New master cylinder

Any thoughts what to check next?

I would say vacuum leak but I took the master cylinder off today after the car sitting overnight and there was a good amount of residual pressure in the system.

Thanks in advance chaps

Stuart

[enuff_zed]

Well now you mention residual pressure I am leaning back towards an air lock.

Forgive me for the daft question but have you definitely got the pipes on the abs unit in the right order. I know there are two different sizes so can't really go that wrong.

Do you have any ABS/DSC codes?

[j3nks79]

If it’s not leaking and you have check the vacuum. Then it must have air in the system.

[bigwinn]

Well now you mention residual pressure I am leaning back towards an air lock.

Forgive me for the daft question but have you definitely got the pipes on the abs unit in the right order. I know there are two different sizes so can't really go that wrong.

Do you have any ABS/DSC codes?

No codes

And yes I did originally get the pipes the wrong way around

But at least I’m fessing up to that

So a damn good bleed needed we think?

[bigwinn]

If it’s not leaking and you have check the vacuum. Then it must have air in the system.

Roger that

[enuff_zed]

bigwinn, to confirm, when I did mine I started rear right, then clockwise round the car to the front right last. That was a conventional bleed, with the pressure bleeder, but not activating the ABS.
Then did the ABS part repeating the four corners in the same order.
For each corner I ran the abs pump twice.

If it helps, I counted ten pulses of the pump in eight seconds every time.

[bigwinn]

Cheers Martin

[Zedebee]

I had a similar problem with OBY after changing the brake pressure sensors. Not much fluid came out, but I must have let some air in nevertheless. I followed Martin’s bleeding guide, but with an extra hand topping up the reservoir, rather than a pump. It worked a treat.

[Zedebee]

In fact I didn’t run the ABS, just did the manual bleed cycle twice.

[bigwinn]

Thanks Ben

I’ll give it a good pump (fnarr fnarr)

[enuff_zed]

In fact I didn’t run the ABS, just did the manual bleed cycle twice.

If you don't disturb the ABS unit you can just do a normal bleed.

[enuff_zed]

Stuart, if it turns out to be air I shall tell everyone you are 'bleeding' useless.

[bigwinn]

Stuart, if it turns out to be air I shall tell everyone you are 'bleeding' useless.

I’ve been called a lot worse

[john-e89]

It’s possible to get air stuck in the calipers, even a thorough bleed doesn’t always shift it. Bleed while clouting the calipers with a rubber hammer has been known to shift an air lock.

[bigwinn]

Bearing in mind one calliper and all lines are new too

Cheers John