Rev1 Excessive Brake Travel after bleeding??

[IMR2T]

Hi guys, never off this feckin forum, ha!

I've got a Rev1, when I got it the pedal was soft and traveled pretty low.

I just fitted Rev2 Front calipers, pads and discs. The rear Rev2 calipers, pads and discs haven't arrived yet so I bleed the entire system front to back - TWICE.

My Rev1 Rear discs are grooved and due needing changed, the pads are low aswell but not enough to fail an mot.

During the bleeding the travel is 1.5-2" and then gets firm and Im happy - then I start the car, take it a drive and the pedal plummets near to the end of travel then firms up!

I've topped up the levels in the large reservoir attached to the master cylinder and also the smaller one to the right(which I'm assuming is an overflow or a clutch reservoir).

What's causung the larger pedal travel on starting the car - what have I missed?

Cheers guys!

[fred130111]

Not sure if this is anything to do with it but I think the Rev2+ have a larger / different master cylinder.

[thomp1983]

the second reservoir is the clutch.

you should be bleeding them, nsr/osr/nsf/osf are you doing them with someone pressing the pedal for you or using a one man kit? have you taken the rear brakes apart at all or removed the calipers?

[IMR2T]

Not sure if this is anything to do with it but I think the Rev2+ have a larger / different master cylinder.

Can I not use the larger calipers with my Rev1 master cylinder?

Just seems strange how until the engine starts the travel and feel it's gd then it just travels another 3-4"??

[IMR2T]

the second reservoir is the clutch.

you should be bleeding them, nsr/osr/nsf/osf are you doing them with someone pressing the pedal for you or using a one man kit? have you taken the rear brakes apart at all or removed the calipers?

That's the exact order I did in both times

Yeah, it was a 2 man bleed.

Bar bleeding the rears I haven't touched them.

[fred130111]

Could be something to do with the brake servo / dodgy vacuum maybe?

[IMR2T]

Ok mate. Wish there was a way to independently test the master cylinder.

[fred130111]

I'm not that clued up to be honest but I would probably try putting the old ones back on to see if it returns to normal?

I'm sure one of the gurus will be able to tell you better than me

[IMR2T]

Same here.

The old calipers both had a siezed piston mate so theyre gubbed.

[androo007]

To be honest compared to other cars I thought the mr2 has the furthest travel before solid grab of any modern car ive owned.

And that's with fresh fluid in too.

[IMR2T]

Aye but not a few inches from the floor, lol

[androo007]

Ohhh I see, no no!

[IMR2T]

Led to believe I need to bleed the brakes with the engine running.

Will try it tomorrow.

[pistol pete]

Led to believe I need to bleed the brakes with the engine running.

Will try it tomorrow.

Nope never had to do that..
Sometimes not right there though..... Hmmm not sure

[bobhatton]

You still have air in the system, keep bleeding till it has all gone

[stuMR2lee]

You still have air in the system, keep bleeding till it has all gone

This^. Make sure every banjo bolt and bleed nipple is tight enough.

Also make sure the rear pistons are wound out far enough to be within 1mm of the pad/disc. The handbrake mechanism can only take up very fine adjustment but no more.

My brakes are very firm using this method and the handbrake holds on 2 clicks.

[IMR2T]

You still have air in the system, keep bleeding till it has all gone

This^. Make sure every banjo bolt and bleed nipple is tight enough.

Also make sure the rear pistons are wound out far enough to be within 1mm of the pad/disc. The handbrake mechanism can only take up very fine adjustment but no more.

My brakes are very firm using this method and the handbrake holds on 2 clicks.

Ok, is it normal to bleed the brakes more than twice?

And would doing it while running the engine make a difference as claimed on other forums?

[stuMR2lee]

If you have air still in the system you'll be bleeding a lot more than that!

The system needs to be fully airtight then it will bleed very easily. If not you have a leak letting in air. Can be caused by poor fitting bleed nipples, brake lines replaced & not tightened enough, and same with the banjo bolt on the caliper.

Person 1: 5 pumps of the pedal & hold.
Person 2: Tube in jar of fluid, bleed nipple open then closed in one movement, watch for fluid bubbling as the air comes out.
Person 2: Release pedal.

Repeat until no more air bubbling in jar.

I'm sure you know that already:D.

Common issue is banjo bolts not tight enough (30NM) or old copper washers.

Never had the engine running doing it.

If you are not getting air out but the travel is too long and brakes don't feel firm it will be the rear pistons incorrectly adjusted.

People think that pumping the pedal adjusts the rear pistons - it doesn't if you study the design. longer piston travel = soft pedal.

[stuMR2lee]

I posted this on the MR2OC a few days ago: I'd also follow Paul Woods guide in the KY2 to set up the piston & handbrake mechanism. Rear brakes & handbrake are poor if you don't wind the piston out until it's an interference fit.

Edit: Looking at this video, and having stripped down many rear calipers the winding in/out of the piston has zero direct effect on the mechanical handbrake mechanism: http://youtu.be/g12uwGnKwlY

The piston merely winds up & down the threaded shaft to set the initial fit. The handbrake lever on the caliper lifts a small pin that in turn raises the whole threaded shaft with piston on it. The piston does not rotate when in use.

What Paul's method ensures is that the caliper is a tight fit over the brake pads. The handbrake levers then only need a small range of movement and are far more effective.

Fluid movement in normal brake use: http://youtu.be/R9jAqP0pqhM

[MartinF]

And would doing it while running the engine make a difference as claimed on other forums?

No difference whatsoever.

It will make the pedal feel different, but it won't change the hydraulic performance.