How much oil is expect to come out? I don't mind getting underneath each wheel un-doing the bleed and leaving a small tray to catch all the oil.....
What you do is put a plastic tube on the bleed nipple and drain into a glass jar or similar, or just wrap a rag around the nipple and absurd the expelled fluid.
But the problem is not with the oil spillage, the thing is that you need to release the bleed nipple while the system is pressurised, let some of the old fluid come out, then quickly lock it back BEFORE the pressure goes down otherwise you will have air drawn back in.
The good old two-man method works like this:
1. One guy in the car, the other guy (usually you – the car guy is the ‘helper') is ready with the spanner around the bleed nipple under the car.
2. Guy with spanner shouts 'press!'. Guy in car presses down the brake pedal in full and shouts back 'pressed!'
3. Guy with spanner opens the bleed screw and watched the squirt of brake fluid come out. As the squirt dies down, spanner guy quickly locks back the nipple. It is important that at this stage the brake pedal is NOT depressed (i.e. NOT released) before the bleed nipple is locked back otherwise air will be sucked back in..
4. When the bleed nipple is safely locked again, spanner guy shouts 'once more!'. Car guy releases the brake pedal, and presses it again in full. Shouts 'Pressed!'
5. This is repeated - if just bleeding, until thick stream with no bubble is coming out - if changing the fluid, until the new (clear) fluid starts coming out from the nipple. At which point you move to the next wheel...
Tips:
1. As you bleed, check the brake fluid reservoir, and top-up as necessary. Don't let the fluid level in the reservoir go down too much or you’ll get air into the system from the top end!
2. If you place a tube on the nipple and submerge it in a jar with some new brake fluid in it, if the nipple does suck-back-in it will collect only brake fluid from the jar and not air.
3. It is advised to push back the callipers to expel the old fluid from them, but very gently and with a flat wooden/plastic tool. You need to
(a) make sure you apply pressure on all of the mating surface of the calliper simultaneously otherwise you may damage the rubber seal.
(b) not use any metal tools as you may scratch the surfaces on the piston or bore.
(c) open the filler cap at the top as well as the bleed nipple while pushing the calliper back, and then push it very gently in order not to create back-pressure and reverse the rubber seals in the master cylinder.
4. take care when opening and closing the bleed nipple. It is a very delicate nut. If it does not open easily, soak it in penetrating oil but do NOT apply brute force with the spanner - the nut will become round or even the whole thing could shear off. When closing, do NOT over-tighten.
5. There is no need to shout, if you roll-down the window the car guy can here you even if you whisper…
If you understand the two man method, you will see that the alternative solutions essentially eliminate one of the two guys - either a fixed air pressure is applied to the reservoir from the top (some use a hand air-pump and container, others like Gunson use the air pressure from the spare tyre) so there is no need to press and de-press the brake pedal as the system is kept constantly under pressure thus eliminating the ‘car guy’, or a one-way valve is placed on the tube at the bleed nipple so there is no need to open and close the nipple with the spanner eliminating the ‘spanner guy’.
