Replacing Master Cylinder

[T-rex]

Hey all,
just chasing some info on replacing the master cylinder, seeing as mine is leaking where it joins the booster and from what I read it seems that I need a new master. I shouldn't have to much trouble swinging the spanners, but what size is the brake line nuts so I can get the right size spanner for it.
And when I change it I'll more than likely go up to the VE brakes, so would it be beneficial to put in a 1" master anyway(even though its not needed for those I read), which leads me to the next question which is will the 1" mate up to the VS booster alright.
And lastly while bleeding I think my teacher way back in college said if I submerge a tube attached to the bleed point in brake fluid and someone pumps the brakes it prevents the air from getting back in the lines.

cheers

[hako]

Read the how-to on doing this job - follow the link below.
Don't rely on memory from years back at school when playing with brakes - research it fully and make sure you know what you are doing!
How To - VT Brake Upgrade

[T-rex]

Ah cheers mate.

[BlackVXGTS]

Make sure you bench bleed the master cylinder before you install it in your car.

[T-rex]

Yeah I was reading up on that, seems easy enough but what happens when you install that master do you just let the fluid drip out as you screw in the thread? Although wouldn't while bleeding the brakes, depress pedal open bleeder close repeat, achieve the same thing? I also should have mentioned college was only 4 years ago thats why I could remember it, but I also just found something that said air can still get past the submerged tube so don't worry about that one. I suppose the only thing I'm not sure of now is whether the 1" will fit straight onto the booster.

Also I just read that air can get into the ABS and stuff it up should I be worried? Is there a way to bleed it if it does?

[The1]

your ment to use a tech1 when bleed abs as the actuator needs to be cycled.

[T-rex]

Mmm thats not good, just having a quick google it seems that ideally I'll want to buy/borrow an OBD1 of some sort that can do that? It seems that it would be cheaper than getting the car tilt trayed to holden or to whoever has one to be bled after I've changed the m/c and brakes.

[The1]

unfortunatly it's commanded from a tech1 scantool only. It's not to say your brakes may not work but you'd have big air bubbles in the abs module so id be doing it. It's also done in a procedural order, bleeding each wheel in a sequence so it needs to be done that way to get all wheels brakes bled properly.

[T-rex]

Ah I see, wouldn't happen to know where I could find one would you? I've just been scouring ebay aus and found nothing. But with that said would it be a preset command or something that only someone who was trained for it know how to do?

[The1]

not in your area sorry, i have one up here. it's only be dealers or perhaps mechanics or auto leckys, though not sure if aftermarket scantools have those functions.

[T-rex]

Fair enough, I couldn't find anything that suggested the aftermarkets did although the computer based ones seemed hopeful but I doubted it, I have some mates who are mechanics so I might see if they can help me, but with some more searching it seems that I might get away with it if I install the master bench bled with full reservoir, so I unfortunately come to a dead end with this it seems. Thanks for your help anyway though.

[hako]

If you bench bleed and have the reservoir full with the cap clipped on plus the brake lines ready to screw to the new MC and spanners to hand etc you should not get any air into the system. The brake lines that you disconnect from the old MC are angled so they stay full of brake fluid - you can visually inspect to make sure. A trick here is to lever back the pad on one of the brake calipers just before you attach the brake lines to the new MC - this forces fluid back up the line and will ensure that the line has no air in it when attaching to the new MC. It's messy this way with brake fluid dripping all over your hands etc (wear gloves and have plenty of rags) but it can be done - it's the usual method ABS or not. If you do find you have soft brakers, take it to an auto-elec with a tech1 to cycle it. Remember to wash all brake fluid away with water immediately after the lines are bolted to the new MC to avoid paint damage. Good Luck.

[Brett_jjj]

If you find that you need to activate the ABS modulator to let any air that may be trapped in the modulator, back through to the brake calipers where it can be bled out, and you dont have access to a tech 1 scantool or similar, you just have to bleed the brakes as normal first up to get them half working, then find a safe area of grass or gravel that you can lock up the brakes on, lock them up a few times, then rebleed them as normal again, any trapped air in the ABS actuator should have passed through the actuator valves as they cycled on/off when the wheels were locked up.
Its suprising how much firmer the brakes can feel after activating the ABS actuators a few times when bleeding the brakes.Ive bled a few ABS equipped commodores with help from the tech1 over the last year or so, and always end up with a firmer pedal than I would if I didnt cycle the ABS a few times.. Some people say that it isnt necessary to cycle the ABS at all, but theres definitely a firmer brake pedal feel to be had if the ABS is cycled properly.

[T-rex]

Thanks for the replies, so it seems that if I'm careful and I still aren't happy with the feel I could just drive to a shop that does brakes nearby and get them to cycle it then that should move the air into the lines as opposed to the ABS, then carefully driving home I can re bleed them then? And yeah that fluid wrecks shit, the leak from the master has gone down the arch below it and theres a big dirty strip of bare metal from where the fluids trickled down, I've been hitting it with a bit of degreaser when I wash the car to try wash it off and counteract it but thats why I want to swap it now.