HELP - Air pushed in to brake fluid reservoir / run dry

[shagi101]

Guys, I need some advise please.

2006 Passat 1.9 TDI

I was doing a simple brake fluid flush as its been at least 6 years since its last change. (fluid that came out looked almost brand new tho)

Managed to bleed all for corners without any problems.

Came to bleed clutch and noticed a few large bubbles of air coming through the bleed nipple, all of a sudden the pressure bleeder started shaking around and I noticed it was pushing tons of air into the brake fluid reservoir. Some how the connector to the pressure bleeders reservoir cap came loose and was drawing in air instead of the new fluid in the tank.

Stopped as soon as I realised what was going on, but it was too late and lots of air had got in. I fitted the connection on correctly and recommenced the bleed at the clutch and managed to get air out.

Drove a mile (without triggering abs) and clutch feels fine, brakes work as before but when keeping constant pressure on the brake pedal it travels further down slowly.

Is there a bleed nipple on the master cylinder?
Do I just bleed all 4 corners and clutch again?

Could air have entered the ABS? I really don't want to faff around with that.

[RichardSEL]

Yes, you have to bleed off at the ABS pump too

Every two years is the regime. I left mine too long before I knew this via this forum. Five years after manufacture year pedal was just starting to "feel" less than hard. Have just had it done again three years after last change. Fluid looked alright but contains increased hydroscopics thus much greater chance of rusting of components I'm told.

Not DOT4 but fluid meeting VW 501 14-B 000 750 and marked as such on the can.

[shagi101]

So, today before doing any further bleeding I drove around a bit and pedal feels much better. With the car running if I hit the pedal and keep pressure on it, it still going down slowly (about an inch maybe) but not very far it does come to a stop a few seconds later. I'm being totally paranoid and thinking this wasnt happening before I attempted this crazy bleed job. Can anyone else comment on this?

Anyhow, I attempted another bleed and did the ABS too. I didnt notice any bubbles coming through at all.

So after a full bleed and abs bleed looks like the brake seem to work as before but pedal still seems to have a bit of down travel when constant pressure is kept on it.... is this normal?

[DMitch16]

Yes it's fairly normal as the servo assist uses air which compresses more than fluid so you get a slight pedal travel after depressing the brakes. If it keeps going down slowly to the floor then you do have a problem!

[shagi101]

Sweet! Thanks Mitch that's put me at ease.