Changed Front Calipers + Brake Fluid

[SiR_RB]

i changed my front calipers from the standard sumitomo r32 gtr calipers to AP racing 6 pot front and braided lines

changed the fluid to motul RBF600, bled the thing sooo many times and when the car is off and you pump the brake pedal it doesnt get firm.

when you start the car there is no pedal feel at all, the pedal goes right down and is very soft

is there ait in the system? does it need MORE bleeding? its driving me insane

also there are no leaks on the calipers or lines and i did bleed the abs unit briefly

please help !!

[GTSBoy]

It's quite possible that you did what everybody does when bleeding the brakes, which is to push the pedal all the way to the floor, which pushes the master cylinder piston down past the point that it normally doesn't go past, into a section of cylinder that is rough/damaged/pitted/grunged-up and you have cut the seal to ribbons and now the master is internally bypassing and needs a rebuild.

[SiR_RB]

its an r33/r34 gtr master cylinder, was on the car when i bought it about 1 year ago and doesnt look very old at all

hope its not the master cylinder ! the resevoir usualy bubbles when you pump the pedal?

[SiR_RB]

also forgot to mention that while bleeding yesterday we accidently let the fluid level go well below "low", stupid mistake...

could their be air in the master cylinder now? even after bleeding it soo many times?

Feels as if the master cylinder isn't squeezing the fluid, as the brake pedal doesn't get firm when the car is off and you pump the brakes

Time to take it to a pro to get it bled properly

Edited September 11, 2011 by SiR_RB

[Moodles2]

Are you bleeding each corner their in the correct order? (I can't remember the actual order, would have to check the service manual)

[blind_elk]

If you let the master cylinder reservoir empty, you need to bleed the master cylinder. Bleed it BEFORE you bleed each corner.

[boiracer]

order is usually furthest wheel first, then in order as you get closer to the master (OR ABS unit?)

when you let the reservoir run low and re-bled it, did you do the rears aswell?? just sounds like air. the issue GTSboy speaks of shouldn't happen with a relatively new cylinder.

we had the same issue when my brother got a full set of after market Discs for his Beetle. we had to bleed it soooooo many times before it came good.

[dori34]

has the car got ABS?

[MrStabby]

From the shop manual;

Bleeding Order

Left rear brake

Right rear brake

Left front brake

Right front brake

Front side ABS (nipple closer to the front of the car)

Rear side ABS (nipple closer to firewall)

Bleeding Method (tho most like to close the bleeder before letting the pedal up, or use a one man bleeder kit)

open bleeder

fully press brake pedal, allow pedal to return, wait 3 seconds

repeat press/return/wait sequence twice more

close bleeder

repeat for each corner and ABS nipples

Also - how does the area of the pistons of the new brakes compare to the old ones? More piston area = mushier feel, but more force on the pad.

[SiR_RB]

cheers for the replys, i coldnt bleed it yesterday as i was busy but im takeing it tomorow to get bled properly...hopefuly its just air in the system

the calipers have 1 big, 1 medium and 1 small piston, definetly looks like it has more surface area

[luke gtr]

According to the workshop manual, you're meant to disconnect the battery before bleeding if the car has abs.

Mine felt the same the other night when I put my new pads and rotors on, and bled a little.

Left it for an hour, and got the feeling back.

Go figure.

Let us know how you go.

[SiR_RB]

Ok just got it back from my mechanic, he bled the master cylinder, abs unit, then the calipers.

The front were full of air cos I was only bleeding the outside nipple, I wasn't aware the AP calipers had 2 nipples each caliper haha

All is good now, brakes like a mofo and definetly out brakes the ku31 265/ tyres I got

Job well done I think

[blind_elk]

Ah, the old "2 bleed nipples on the caliper" trick. That's the third time this year I've fallen for that one!