I have changed master brake cylinder and the oil at this car service, they did the bleeding where they used this pressure pump that connects to each caliper at the time, the thing just sucks the fluid and the air out, with no brake pedal pumping.The procedure was FL,FR,RL,RR.
I've read online that there is ABS bleeding that is done with VAG diagnostics, was this something that they've should have done also?

 

I haven't heard of that - and VAG COM can't bleed brakes.

 

I they use VAG to simply activate the pump during the bleeding, pushing the pedal or vacum pump is still needed.

 

Yeah, that's exactly what he's doing, but that's only because he has to bleed the entire system. If you're just doing a typical brake job, that's unnecessary. You can just pump and hold the brakes three times. That will ensure there is no air in that corner and it will drain some of the old fluid.

 

I think i need to do this, since i changed the master cylinder and the oil was completely changed.
The problem is that it was done without activating the pump with VAG, they simply disconnected the lines from ABS to the wheels and they pushed the pedal until the air came out.After that the pedal was good, but the next day pedal was mushy and soft again like it was before.

 

Sounds like you might have a few air pockets in the abs pump, best practice is to bleed with the diagnostic tools as shown in the video above.

 

+1

If you have access to it, always use best practices. The "Pump, Hold and Bleed" at the caliper is the best practice for someone who has no access to (or money for) the full VAG cycle.

Something is always better than nothing in this situation.
.

 

Ok cool thank you guys.
One more question, is it possible to bleed the system using vacuum that sucks the air and fluid when connected to the calipers, without using the pedal pumping method?If possible, is this system better than the old fashion pedal pumping method?
I've read that the master brake cylinder can be damaged during the bleeding by pedal pumping.

 

There is a pump system you can buy, but I don't really like it. I've been bleeding brakes with the pedal for 25 years and never had a problem with Master Cylinder damage. Your car operates that way normally (applying pressure to the pedal).

 

If theres corrosion in the master cylinder bore, from moisture thats been absorbed by the brake fluid.
When you push the brake pedal to the floor, the piston can go past its normal travel distance & its seals will go over the corrosion ( rust ) & ruin the seals.
I had this problem with a different car, a Ford Cortina. I ended up getting a reconditioned master cylinder with a StainlessSteel bore liner in it.
That fixed it.
Later i had a Nissan Leopard TRX ( my God i wish I still had it ) they 'Vacuum bled' its brake system. Great idea.
I tried a vacuum kit on my A4 & it didnt seem to work, I just pedal push bled it a bit after changing brake pads.
It seems pressure bleedings the way to do it.

Also, every brake resiviour i see seems to be badly corroded on its top rear side. Probably to do with sunlight getting under the bonnets top edge.
Probably a mandatory replacement @ 210,000 kms