Bleeding Issue After Fitting Vec V6 Brakes

[HARBER07]

I can't get a decent pedal feel!
I've just finished the 5 stud conversion to my mk3 Astra GSi, using complete Vectra 288mm fronts and 286mm rear hubs with Astra calipers. The rear calipers were just unbolted and bolted back on, so guessed no bleeding was needed here. The front calipers were stripped, cleaned and rebuilt with new seals etc. and prior to swapping the calipers the hoses were clamped off to reduce fluid loss.

Now I've bled the 2 fronts using the pedal method, and using an ezi-bleed kit, and can't really get a good feel on the pedal at all! I've done a test run on a local air field and I do get braking effort eventually, but the pedal is pretty much on the floor. I don't know if this is an ABS related problem or not?. I've done a run with the ABS fuse out but it doesn't really make a difference IMHO.

Please help? lol

Cheers.

[Paul]

Calipers on the right way round at front?

[HARBER07]

The funny thing is, I made a mental note to not forget to put that, and forgot . But yes, both on the right way, bleed nipple at the top.

[thedondy]

try bleeding the rears?

[dewismotorsport]

It sounds like your suffering from having the wrong size master cylinder for them brakes as the pistons are quite large, common problem when upgrading to v6 brakes everyone moans the pedal feel is crap and on the floor

[munsterbigfeet]

I've had ****e brakes on mk3 after doing the same, turns out seals went pear shaped when pushing originals back when removing the calipers. Put another master cylinder on and was ok. Might also be worth a couple of taps with a hammer on the end of the master cylinder in case the seals are stuck....

[HARBER07]

Thanks for the replies guys. Would a Vectra MC be a direct replacement for the Astra one then?. I don't really mind what I have to do, but I'm not 100% confident in the brakes ATM!. To be honest I never checked the bore size, and just assumed they were the same.

[Gordo]

There shouldn't be much difference in the pedal travel, even with the larger front caliper pistons - what may have happenned, assuming you're bleeding them properly*, is that there was some rust or other gunk in the master cylinder that's affecting the piston seal. Wouldn't hurt to give it a clean out and maybe hone and a seal kit.


*If the bleed screws are too loose, it may be drawing some air back past the threads, but it's rare - I generally just use a 1/4 to 1/2 turn max'.

[HARBER07]

Thanks mate. I'll try and bleed the whole system today and see where that gets me, then check out the MC. As you rightly said there could be a bad section in there that the piston never used to go near, but putting the pedal to the floor has now revealed. I'm pretty confident the calipers are fine as I re-sealed them and there are no signs of leakage whatsoever!.

[HARBER07]

Winning!. I've spent all morning bleeding everything using various methods, but after bleeding the master first, then using an ezi-bleed and stomping on the pedal with the engine running, I now have a decent feel to the pedal. I still have a bit more travel than I used to, but everybody is pretty much telling me thats normal.