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Bleeding brakes

M

Monkeythree

New member
Is there a trick to getting S2 Brembos to bleed properly? I've been at mine for ages and struggling to get any meaningful amount of fluid through the rears. Have had an assistant pumping the brake pedal for 40 minutes this morning and I've switched to a vacuum pump this afternoon because i was working single handed. Not having much joy with either method really. The front right is pulling through clean, the front left is still pretty frothy and the rears are 90% air with the odd splutter of fluid here and there.

The system was completely empty when I started because I've changed several lines and all the hoses.

Any suggestions?
 
I speak from experience. (If you are using the spare tyre method - make sure you have got enough pressure in it beforehand and then lower it to the pressure limit recommended with the kit). Use AP660 fluid. Do not drain the fluid totally - not always a problem - but it does introduce air into the system. Remember - each corner may have TWO bleed nipples. Doesn't really matter which order you bleed these - I start with the outer one each time. Use a ring spanner on the bleed nipples - don't be tempted to use 'Ein Englander'. Start at the rear right-hand side, then rear left, then front right and finally front left. i.e. Start with the furthest away from the reservoir. As you bleed each nipple you will get air bubbles coming out into your jar. Continue for a while as you will not see the smallest air-bubbles. Try not to let the fluid level drop below minimum level in the reservoir. Top up as necessary - after releasing the pressure. You're likely to use at least a litre for a full system bleed - perhaps 2 litres. Get plenty of back-up supplies - a lot easier than trying to find the fluid you want on a Sunday at 4pm. You may have to repeat the cycle a few times to get a hard pedal.
 
If the system is empty and you are doing all 4 brakes then have the car level if its just the rear then lift the front a bit. It doesn't have to be pointing at the stars just up a bit. Then what I do is open all the bleed nipples that you are going to bleed.Then fill the reservoir and wait till you get fluid coming out of the bleed nipples. ( don't worry it will not run out at a tremendous rate more of a dribble. Then close the nipples and bleed one at a time starting with the caliper that is furthest away from the master cylinder.This way you will have fluid in the pipes before you start.
 
System is (was) empty and the car is level on 4 axle stands. Bit tricky to start tilting it now. I had started with the right rear because conventional wisdom says furthest from the MC first but i got fed up after 20 minutes of getting only the merest dribble of fluid through to the back and switched to the fronts instead. Front right has now bled pretty well but front left is still very bubbly. My current thinking is to try to get the fronts full of fluid and then with less air in the overall system, the rears might eventually bleed through. I'm not convinced by the vacuum pump method because i don't believe the threads on the bleed nipples are airtight so as soon as the nipple is open, the vacuum pump must draw some air down the threads, thus reducing the vacuum effect on the brake line. That's my theory anyway. As luck would have it, I've managed to find a Gunsons Eazi Bleed in the archives this evening and amazingly I even have a cap which fits the S2 MC reservoir so I'm going to have go with that tomorrow. Mrs M3 is working from home tomorrow so I will recruit her as pedal pusher and hopefully the combination of the Eazi bleed and forced manual labour will do the trick.
 
If the system is empty then open all the bleed nipples and fill the reservoir until it drips from all the nipples then you will have fluid in the pipes and be able to bleed it.Having the car level on stands will help you with this.
 
Sounds like the master cylinder needs priming or you may be drawing air into the system. Have you checked all your new connections? If you're having trouble getting fluid to each corner, disconnect at the calliper, push fluid through the line then reconnect. Do this for each corner, then try bleeding as normal. Some systems can be real pig when fully evacuated. I remember having one system where it was necessary to remove and hold the calliper during bleeding so the bleed nipple was upright in order to expel all the air. If your still having trouble, it could be a faulty master cylinder. Regards, Clive.
 
I'm not saying anyone else would be so stupid as to make the same mistake I made but you have noticed that there is an inner bleed nipple as well as an outer one?
 
Success! Tried leaving the nipples open overnight Colin but it seems that ambient air pressure and gravity were not enough to push the fluid through the system. What it needed was positive pressure on the MC reservoir. I filled and connected my 20yr old Gunsons Eazi bleed this morning and after a brief gurgle there was a satisfying "whoooosh" and the entire contents (about half a pint) of the Eazi bleed bottle injected themselves into the system. After re-filling the Eazi Bleed, I connected up again and then went round all the nipples in turn starting from the rear right and every one came through clean within a second or two. So it seems that having had the system drained down completely there was simply such a huge volume of air that the small displacement of the MC piston wasn't sufficient to move it and the vacuum pump just didn't have the oooomph to pull the fluid round the tortuous circuit. So handy hint for anyone who needs to refill an empty system is to start with an Eazi Bleed!
 
I am late to the party here but concur that vacuum bleeding doesn't work because air leaks in past the bleed nipple thread and that is the path least resistant. A gunson eezibleed is the way forward!
 
That what was I concluded after 20 mins of furious suction Rob. I contemplated PTFE taping the threads to test the theory but couldn't be bothered doing all 8 of them. Was quite relieved when I rummaged in my tool chest and found my 20yr old Eazi bleed there because I only brought essential tools out here with me and I thought it might be back in the UK. Needed a bit of a clean up but worked perfectly.
 
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