Need to Remove Caliper to Bleed (Flush) Brakes
 

I have never taken a caliper off to flush the brake fluid on a car (but my experience is limited to 911s, an RX-7 and a BMW 2002).

But a poster on the Vanagon forum stated one should push the caliper pistons back to get all the old fluid out when flushing out old fluid - I'm wondering if there is a reservoir of old fluid left in the calipers of some (or all) disc brake systems that is not pushed out by the new fluid...

This procedure was posted as an example - it shows how to push the piston back for pad replacement:
How to Replace Front Brake Pads : Compressing Caliper for Brake Pads - YouTube!

There can be residual fluid still in the system behind the pistons. It depends on the method used to flush out the fluid and also the style of caliper.

I use compressed air to force out the pistons, change the o'rings and clean everything up. Put it back together and use fresh fluid.

Is the caliper different from let's say a Porsche caliper? Cracking the bleeder and pushing out fluid will get *basically* all the fluid changed from behind the piston...unless the vw caliper is different? Just thinking out loud so don't trust me!

The posted video is the process used to push the pistons back in so new brake pads can fit properly on the rotor. The old pads wore down causing the pistons to extend further in order for the pads to make contact. There is no reason to do this simply to flush the brake fluid.

That's what I always thought - not sure how the VW caliper is made, but I assume it is Ate or similar.

I guess there might be some residual older fluid behind the piston, but unless its incompatible with the new stuff, you dont need a 100% flush unless somehow it was so contaminated... in that case you probably need a caliper rebuild anyway...

Outfit the calipers with SpeedBleeders.

Top up the reservoir with new fluid.
Pump until clean fluid comes out of each bleeder.


KT

Water is heavier than brake fluid, so if you have a really contaminated system, you might want to think on that.