StratfordShark

I want to completely flush my old brake fluid (have Racing Blue to put in so I can see the new stuff!).

With the Brembo 4 Piston callipers, what is correct sequence for opening the inner and outer bleed valves? Does order matter, and do you have to leave one open when you bleed the other?

As a matter of interest, why are there 2 bleed valves?

Thanks for advice/info

IcemanG17

There are 2 bleed valves due to the 4 piston design...each bleeder is for 2 pistons.....in theory the outer bleeder also bleeds the inner piston...but that can't be ideal or Brembo wouldn't have made them that way....

What I do is use a motive power bleeder...remove as much fluid as possible from the tank....then start at the inner right rear....once its good then do the outer.....switch to the left rear inner then outer then move to the front etc....

A new idea I'm gonna try is to bleed one side at a time (front and rear)...which will eliminate the safety bar in the master from engaging.....so I'll do the passenger side 1st and do both inners then both outers.....then switch to the drivers side...

928ntslow

Unlike lesser style braking components out there, this style Brembo applies direct and equal pressure to the disc from both sides. Old Porsche models and many other calipers out there use the clamping force from one side method. There are normally one or two pistons applying direct pressure to the inside of the disc (via the brake pad) while the outside is just clamped and pulled in. You get uneven brake wear at best on all of these style brakes and the braking force is not as good. While having 2+2 piston calipers (there are 3+3's and 4+4's out there also...peobably more as well), you basically have a 2 in 1 braking system.... 2 sets of pistons with 2 fluid chambers on one caliper. If you didn't have the individual bleeders, you would be sending bad fluid into one chamber or the other when you change pads and recess the pistons. It's never a good idea to push used brake fluid which has been heated to temps well over 500 degrees back into the hydraulic system. The molecular properties of the fluid changes under several heated cycles and becomes "gummy" (I think) and corrosive. An annual flush is the advised thing to do whether you think you need it or not.

Now, since there are two chambers, you need to bleed the inside (closest) chamber first to expel all bad fluid, then of course close that and move to the outside chamber.

I just bought a power bleeder and it is the best $30 some odd dollars I have spent. pumping the brake pedal with someone in the car does not give the continuous flow of fluid and some always gets sucked back up in the line. The power bleeder is awesome and you work at your own pace nice and evenly guaranteeing no air in the lines.

Hope this helps.

Not sure I understand the "one side at a time" Brian.

GUMBALL

The caliper is made of 2 chambers (2 sides), and any bubbles will rise to the top of each chamber, so to purge the caliper properly, that's where the bleeds must be situated.

And IcemanG17 has the correct procedure - do a front caliper and a rear caliper simultaneously.

FlyingDog

Bleeding just the outside would not bleed the inside since air is light than brake fluid and the crossover is at the bottom. It would also drag any solids through the crossover which could clog it.

mark kibort

there is an inner bleeder screw???? oh well

mk

whitefox

I work at a brake shop so I put my car up on the lift and bled the brakes, I looked up the sequence in a book we have and it just said "bleed the brakes". I bled the outer one first though, looks like I messed up, I flushed a ton of fluid through it though, the old fluid was orange.

StratfordShark

Thanks everyone for great advice and - as ever on Rennlist - an education!

GUMBALL

For some reason pushing fluid back into the system when changing pads seems to confuse the ABS system. The result is a soft pedal that takes a LOT of bleeding to rectify.

jon928se

If you are changing the brake fluid completely then Outer first.

The inlet to the caliper is at the top of the inner chamber. By bleeding the outer first the new fluid enters the top of the inner chamber, flows down to the bottom of the inner chamber taking all the old fluid before it, through the pipe at the bottom of the caliper and then up into the outer chamber.

This way you expel most of the old fluid without mixing it with the new (which just wastes new fluid)

When the fluid is mostly new, then you can bleed it to get rid of air (there shouldn't be any but there probably will be some) then you go inner bleeder first to remove all the air in the side of the system nearest to the master cylinder) as there's only a small pipe at the bottom of the caliper between inner and outer, bleeding the inner just leaves the outer as it was.Then bleed the outer and the fluid you are getting is the new recently bled air free fluid from the inner half.

Gary Knox

As an added suggestion - don't forget the bleed screw on the front of the master cylinder AFTER you have done all the rest of the 8 caliper bleed screws. It is a smaller size (7 mm wrench, as I recall).

Gary Knox
West Chester, PA

Charley B

So let me make sure I'm getting this. If you're changing fluid you would start bleeding outer RR then inner RR etc. on through the system until fluid is replaced and then go back and bleed inner RR and RF, then outer RR and RF, then left side, then master, to remove any leftover air. Is that the idea?

fabric

I thought you bled this first? It is definitely a smaller size.

StratfordShark

Just to add to the confusion, my understanding was that you bleed the MC first and last? That's what I did last time I bled the brakes anyway. It is a 7mm bleeder.

Jim bailey - 928 International

It is like the 100 year old chinese soup where they have been cooking it every day and simply add to it every day ....there is always a little of the old mixed in with the new ! even after 100 years Diagonal bleeding makes some sense on pre ABS cars where one of the master cylider pistons feeds a front and a rear. ABS cars one piston feeds the fronts the other the rears.