2013 Mk7 Golf brake and clutch fluid renewal question.

[sardine]

Since I'm new here, I posted this in the newbie's forum a few days ago. I didn't get any reply so I re-post it here, hoping that non-newbies may have an answer.

---------------- The post in the newbie forum:
Newbie here with a 2013 Golf Mk7 1.4TSI 90kW manual, bought new in 2013.
First time I owned a VW, all my other cars are Volvo.

I renewed the brake fluid today for the first time, the last few times were done by the dealership.The brake fluid renewal procedure I used is as specified by the VW Mk7 workshop manual that I bought online.

The first part is brake fluid renewal, everything seem normal.

The workshop procedure requires the clutch fluid to be renewed also. This is where it got weird.
After removing some 100ml of fluid from the clutch nipple suddenly a lots of air came out. The fluid reservoir level is still between min and max, i.e. no air is coming from the reservoir.

The procedure then requires the clutch nipple to be closed and the clutch pedal press and release some 15 times.

In the second stage, the first 50 or so millilitre is ok, then air again. When I closed the nipple and test, there was no clutch. I could not get into gear. Bled another 10 or so millilitres of fluid and the clutch came back. When I went for a test drive there was nothing wrong.Have anybody had this problem? Any guess what's going on here, anything to worry about?

---------------------- End of newbie forum post

I just don't know where the air come from and which bit to check. The amount of air coming out seems to be too much to be trapped air. This of course is only a guess, it's possible that there it could be lots of trapped air.
Does any of you know where the air may be entering the system, if it was not trapped air? Should I just keep on bleeding?

[clio]

sometimes air can make its way via the thread of the loosened bleeder nipple

[sardine]

sometimes air can make its way via the thread of the loosened bleeder nipple

Could be, but the air came out rather forcefully though.

Just to let other members know, I've now come to believe that the air that was expelled during the bleeding process was just compressed trapped air. The reason is, I bled some more this morning, ~60ml, and there was no more air coming out, the clutch remained firm. So, if this happened to you, then just keep bleeding, say another 100ml. It's probably not a break in the line, given that the air come out a bit forcefully.

[brad]

If there was air in the system then the clutch pedal should have been spongy before you even started bleeding

[sardine]

I don't know the Golf clutch well enough to know if trapped air could be hiding in there without making the clutch pedal spongy. The path from the slave cylinder back to the reservoir , I'm sure is without break. So, where is the air coming from?
The brake fluid from the clutch is kind of greenish, suggesting that the clutch fluid was never renewed all those years by the dealer. They are supposed to renew the fluid but perhaps didn't. Whether this is a contributing factor, I don't know.