fearofweapons Posted August 19, 2014 Share Posted August 19, 2014 So I have serviced my master brake cylinder ( http://forums.lr4x4.com/index.php?showtopic=90537 ) and replaced it in the vehicle. I filled the reservoir and then pumped the brake pedal - all squishy as I would expect. So out with the Brake Bleeding kit and bleed through starting on rear near side - hum no bubbles seen. Bleed all around and get some bubbles at front offside. Brake pedal is now a bit firmer but not as it was before servicing the master cylinder. (BTW no leaks see at the Master Cylinder.) It's now 22:00 so time to pack up. Plan is to have another go at bleeding the brakes through (probably Wednesday evening.) However I recall reading in some threads on some forums differing opinions about how to remove air after major brake work. Some seemed to imply leaving the system for a while to let air try and work it's way back to the top (but then if that's true why do we have to bleed?) Some implied taking the motor for a drive would shake the air up and allow it to move to the reservoir and escape. Again though if this were true why would we ever need to bleed the brakes? Still others indicated that it was just a case of 'flushing' the system through with lots of brake fluid to push the air out. I must admit this seems to logical approach to me - however we are talking land Rovers here so... I am leaning towards operating the brake pedal through a few cycles in the hope this pushes the air towards the bleed points and then bleeding again. Of the four options which gets your seal of approval and why? Or would you suggest some other course of action and why? as always any help gratefully received. regards, Richard Quote Link to comment Share on other sites More sharing options...
dirtyninety Posted August 19, 2014 Share Posted August 19, 2014 Leave it over night, a lot of the fine bubbles will settle into larger bubbles and thus be easier to bleed out. You could even park with the bonnet aiming up hill to try and aid the bubbles to work towards the reservoir. I must say, weve replaced entire systems (calipers, pipes and master cylinder) and not ever had any great problems. Just tend to get it so you can stop, then advise to observe and top up the brake system the next day. Quote Link to comment Share on other sites More sharing options...
western Posted August 19, 2014 Share Posted August 19, 2014 after my chassis change when we got to bleeding the braking system [disc all round] we opened all the bleed screws kept the master cylinder topped up & left it for 30 mins, fresh air free fluid was showing at each bleed screw, we nipped them up then bled each caliper in turn, brakes have been great since. might be worth a try. Quote Link to comment Share on other sites More sharing options...
Eightpot Posted August 19, 2014 Share Posted August 19, 2014 Check that your bleed nipples are clear and will actually pass fluid through - quite common for them to get filled with crud & rust. Remove one completely and check the small hole in the bottom of the bleed screw is clear. Quote Link to comment Share on other sites More sharing options...
Disco-Ron Posted August 19, 2014 Share Posted August 19, 2014 I use a vacuum bleeder that works off the compressor, and sucks the fluid through..... never failed yet.... Quote Link to comment Share on other sites More sharing options...
Scotts90 Posted August 19, 2014 Share Posted August 19, 2014 3/4 gets my vote. My dad was an old school mechanic and taught me that way...always handy to have a helper...pedal down slow with the nipple open...hold down, tighten nipple....pedal back up...loosen nipple and repeat. As the fluid runs clear and bubble free you can tighten the nipple on the downward stroke and this should lead to a firm pedal. Never had a problem doing it this way Quote Link to comment Share on other sites More sharing options...
mickeyw Posted August 20, 2014 Share Posted August 20, 2014 (edited) Check that your bleed nipples are clear and will actually pass fluid through - quite common for them to get filled with crud & rust. Remove one completely and check the small hole in the bottom of the bleed screw is clear. This is what I was going to say. I had this exact problem trying to bleed my clutch slave cylinder last weekend. Luckily the fluid got past the threads of the nipple rather than through it, otherwise I would have easily though something else was amiss. Another trick I have heard in the past is to pump the pedal up hard, then leave it wedged down with a lump of wood/brick/whatever you have to hand, and leave things to settle for a while before further bleeding attempts. Edit to add: I was able to clear the nipple with a small drill. After bleeding I fitted a dust cover - hopefully this will avoid a repeat performance in future. Edited August 20, 2014 by mickeyw Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted August 20, 2014 Share Posted August 20, 2014 The wedging the pedal with a bit of wood trick Mickey mentions should work, I've used a similar trick on motorbikes in the past, on a motorbike if you bungeed the brake lever to the handle bars and left it over night you would have really sharp brakes in the morning. Supposedly it makes trapped air raise up to the master cylinder Quote Link to comment Share on other sites More sharing options...
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