09-06-2016, 06:46 PM
(This post was last modified: 09-06-2016, 06:51 PM by pug306driver.)
Hi iaitoo,
If the master cylinder has been allowed to empty, ( or a new one/resealed on fitted ) then its best to prime it first of all, by filling the res and allowing some dripping to take place from the m/cyl pipe union holes, caught with rag.
When you are sure the cylinder is primed, say 20 drips form each hole, fit pipes ( they should be ready to fit and in place, only needing to be screwed in and tightend ) and tighten, washing any fluid spillage with water. The m/cyl is now very wet with fluid inside and ok to use the pedal.
Remember that the master cylinder is a pump, pumping fluid out, which, when the system is up and running, is returned to the master cyl res, apart form the fluid "used" during caliper self adjustment.
Since the pipes from the m/cyl to the abs unit are above the level of the m/cyl, then undo the feed pipes on the abs and prime them also, after that ( possibly undo the pipes from the abs unit to wheels and watch for fluid dripping, then do up tight ) it should be all down hill, apart from possibly the feed pipe from the abs to the r/h/s of car.
If when replacing pipes, some "pipe end caps" ( flare for cap formed on scrap pipe, union fitted and "open end of pipe flattened and folded thus sealing" ) are fitted, the cylinder will not empty, and gravity ( syphon ) can change the fluid for you, drip by drip.
With a sucker ( dedicated hydrometer body minus float, just for brake fluid only ) most of the old discolured fluid can be sucked out from the res.
Add new fluid to res to "disturb" any black crap in the res and suck it out, add some more new fluid and repeat until only clean fluid is sucked out. From this point onwards, only new clean fluid is making its way thru the system, pushing old fluid out.
If fluid is caught in a jar, and after say 200 drips for the furthest nipple, the old fluid is emptied and new fluid collected, you will see the new fluid cos of the colour change. New looking rather than discoloured
Alternatively, a pressure fluid feed to the m/cyl res will prime and fill the system to the bleed nipples.
There is a tiny tiny hole in each chamber of the m/cyl which allows fluid to flow by gravity, which if blocked, will not allow gravity flow to happen. This hole is not seen unless the res is removed, but if the caliper pistons can be pushed home, and the fluid level in the res rises, then this hole is clear. If this hole is blocked, then you will have trouble bleeding the system and the brakes will tend to not want to release, in fact, will lock on and stay on until system has cooled down.
Make sure the holes in the bleed nipples are clear, else they will not pass fluid.
Engine off and all vacuum used by pumping the pedal several times, allow to rest. If pedal now hard when pressed, a good hard short travel pedal means no air in system, a spongy pedal means air still in system.
With pedal pressed and engine started, the brake pedal goes down more, means vacuum and servo works. Check for leaks on pipes, unions, calipers, master cylinder to servo and res to master cylinder.
You say you have to press the pedal quite far before brakes work, how far, ours has abs and brakes very keen with not much pedal travel, powerful brakes but had brakes serviced xmas time, new pipes, new hoses, new discs, new front caliper seals and all calipers/pads lubed. (slide pins and pad slide contact areas )
If the master cylinder has been allowed to empty, ( or a new one/resealed on fitted ) then its best to prime it first of all, by filling the res and allowing some dripping to take place from the m/cyl pipe union holes, caught with rag.
When you are sure the cylinder is primed, say 20 drips form each hole, fit pipes ( they should be ready to fit and in place, only needing to be screwed in and tightend ) and tighten, washing any fluid spillage with water. The m/cyl is now very wet with fluid inside and ok to use the pedal.
Remember that the master cylinder is a pump, pumping fluid out, which, when the system is up and running, is returned to the master cyl res, apart form the fluid "used" during caliper self adjustment.
Since the pipes from the m/cyl to the abs unit are above the level of the m/cyl, then undo the feed pipes on the abs and prime them also, after that ( possibly undo the pipes from the abs unit to wheels and watch for fluid dripping, then do up tight ) it should be all down hill, apart from possibly the feed pipe from the abs to the r/h/s of car.
If when replacing pipes, some "pipe end caps" ( flare for cap formed on scrap pipe, union fitted and "open end of pipe flattened and folded thus sealing" ) are fitted, the cylinder will not empty, and gravity ( syphon ) can change the fluid for you, drip by drip.
With a sucker ( dedicated hydrometer body minus float, just for brake fluid only ) most of the old discolured fluid can be sucked out from the res.
Add new fluid to res to "disturb" any black crap in the res and suck it out, add some more new fluid and repeat until only clean fluid is sucked out. From this point onwards, only new clean fluid is making its way thru the system, pushing old fluid out.
If fluid is caught in a jar, and after say 200 drips for the furthest nipple, the old fluid is emptied and new fluid collected, you will see the new fluid cos of the colour change. New looking rather than discoloured
Alternatively, a pressure fluid feed to the m/cyl res will prime and fill the system to the bleed nipples.
There is a tiny tiny hole in each chamber of the m/cyl which allows fluid to flow by gravity, which if blocked, will not allow gravity flow to happen. This hole is not seen unless the res is removed, but if the caliper pistons can be pushed home, and the fluid level in the res rises, then this hole is clear. If this hole is blocked, then you will have trouble bleeding the system and the brakes will tend to not want to release, in fact, will lock on and stay on until system has cooled down.
Make sure the holes in the bleed nipples are clear, else they will not pass fluid.
Engine off and all vacuum used by pumping the pedal several times, allow to rest. If pedal now hard when pressed, a good hard short travel pedal means no air in system, a spongy pedal means air still in system.
With pedal pressed and engine started, the brake pedal goes down more, means vacuum and servo works. Check for leaks on pipes, unions, calipers, master cylinder to servo and res to master cylinder.
You say you have to press the pedal quite far before brakes work, how far, ours has abs and brakes very keen with not much pedal travel, powerful brakes but had brakes serviced xmas time, new pipes, new hoses, new discs, new front caliper seals and all calipers/pads lubed. (slide pins and pad slide contact areas )