Antnicuk
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| posted on 25/5/11 at 07:48 PM |
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Brake Bleeding Tips Needed Please
I have always had a very firm brake pedal with my dual cylinder pedal box on the stylus. I have a track day coming up so i thought i would bleed the
brakes, i use an eazibleed which pressurises the system using air pressure from a tyre. I have used this in the past with no problem. I made the
mistake of running it dry while doing the rears and pumped air into the system. Since then i have been unable to bleed them. I have put several
litres of brake fluid though the system and i still have no back brakes. The pedal is really spongy.
I have left the car with a broom handle compressing the pedal as i have been told that this forces air back to the resovoir. I have also tried fresh
fluid 3 times and it appears that very little air is coming out (sometimes none) but still i have a spongy pedal.
Just wondered if anyone had any tips, i only have a week till the trackday and having no brakes could really ruin it!
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rusty nuts
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| posted on 25/5/11 at 07:59 PM |
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What type or rear brakes do you have ? If rear discs are the bleed nipples at the top ? if not take the caliper off without disconnecting the hose,
slacken off the handbrake cable and place a piece of wood between the pads and turn the caliper so the bleed nipple is at the top before bleeding.
Holding the brake pedal down compresses any air into micro bubbles which will eventually form a larger air bubble according to my old college lecturer
many years ago
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Doctor Derek Doctors
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| posted on 25/5/11 at 08:02 PM |
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Those easy-bleed things are a recipe for disaster, just get another person to help you out.
Get one of the bleed pipes with a one way valve (about £3 from Halfords) put it on the nipple, crack the nipple and get someone to start pumping (not
too violently), usually 5-10 pumps before tightening the nipple (on the down stroke) and then topping up the resevoir.
You should be able to spot air-bubbles coming out of the caliper through the clear tube. Check the pedal feel after every top up to see if its any
firmer.
Once you think you have clear the air do a final few pumps where you get the other person to put light pressure on the pedal, crack the nipple, press
the pedal to the floor then imediately lock off the nipple with the pedal still down, then allow the pedal back-up, do this about 5 times to clear any
final remnants of air.
If this doesn't clear the system then i would suggest some light driving to try and get the air to the caliper, then I would park the car with
the rear end up on some ramps or jack so that the caliper nipples are the highest point of the brake system, this may help get the air to the
nipple.
It can be a nightmare though, when I changed the rear axle on my E30, it took 3 attempts of the above routine to clear the air in the rear lines.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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britishtrident
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| posted on 25/5/11 at 08:15 PM |
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Even with an Eezibleed the pedal needs a couple of pumps to prime the master cylinder.
The other trick is pull a pad out pump the calliper piston out a little and then push it back to push the fluid back to the master cylinder.
[Edited on 25/5/11 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Antnicuk
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| posted on 25/5/11 at 09:46 PM |
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thanks uys, i will give it ago with some one pumping the pedle, i think i will also try removing the caliper to ensure he nipple is up!
600 BHP per ton, Stylus Brought back from the dead! Turbo Rotary Powered!
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RazMan
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| posted on 26/5/11 at 06:58 AM |
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I have had a few problems with the Eazibleed in the past and air seems to get trapped in the M/C unless the pedal is pumped. This is a particular
problem if the system has sucked a lot of air (if the level gets too low) and in that case there is no substitute for SWMBO's foot 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RACER101
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| posted on 26/5/11 at 08:56 AM |
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On twin cylinder sytems I have often found that it helps to completely disconnect the front cylinder (remove the clevis pin on the bias bar) when
bleeding the rears (and vice versa).
Probably sounds weird but, depending on the design of the pedal box, leaving the front cylinder connected can prevent the rear cylinder from moving
through its full length of travel. Any air in the cylinder, brake lines and rear calipers seems to be purged much more effectively if you can get the
pistion in the rear cylinder to operate through its full stroke when bleeding.
This is a problem I have encountered on several different race cars fitted with twin cylinder bias adjustable pedal boxes and bleeding each cylinder
independently (and often also removing & repositioning the caliper as suggested above) invariably solved the problem.
Good luck.
John
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