DimaA6_ABC_Kiev

New Brembo 4-piston calipers (fitted even on 2.0 TFSI/TDI) have 2 valves, on front (visible through the rim, covered with rubber cap) and back (not visible from outside). Is it necessary to bleed brake fluid from inner valve as well, or will outer be enough?

spijun

Mistaken, Brembo has a 2-piston calipers on 2.0 and 3.0 (TDI, TFSI)

Only one valve is used. Curiosity, why are you doing this




Here is picture
Search 8R0615107E - 8R0615107E - Front Brake Caliper - Left - ES#2707079

DimaA6_ABC_Kiev

Thank you for the link to caliper images from different angles. Let's take a look at this picture - it clearly shows 2 bleeder valves:



Now, let me show 4 pistons. The image above shows a piston seen through the bracket used to attach caliper to some suspension parts. This proves outter part of the caliper (closer to the viewer, closer to the rim spokes) has pistons. And then rest of the pictures prove that inner part (the one with bracket) has 2 pistons:



Answering your question why Q5 owner would bleed the brakes - because brake fluid deteriorates with time (mostly because it absorbs the moisture) and boils at lower temperatures than new. This is recommended by car manufacturers, interval is 2 years or 50K kms.

spijun

See the photo below that I set, it is from electronic service manuals and where it was explained that it uses only one bleeder valves

This must be done on all brake calipers

HerrK

With a fixed caliper system you need to bleed both sides for optimal performance. You will never get all the old fluid out of system bleeding only one side. Inboard bleeder first followed by outboard bleeder. This minimizes the cross contamination of the fluid since the line from the master is connected to the inner and the crossover hard line is on the bottom of the caliper.

Older floating systems as shown by "spijun" only have pistons on one side of the caliper and hence only one side needs/can to be bleed.

DimaA6_ABC_Kiev

Very logical statement, thank you! Will follow.