And, if gravity bleed, what is the procedure?
The Old Gray 320i that is my screen name up and running, but I really need to flush brake the lines.
Looking for the best way to go about it.
And, if gravity bleed, what is the procedure?
The Old Gray 320i that is my screen name up and running, but I really need to flush brake the lines.
Looking for the best way to go about it.
Vacuum bleed works well for me. But I have to put grease around the bleed nipple threads so that air does not get sucked in past the threads.
If you don't have a vacuum bleeder, steal one of your wife's plant sprayers or and pull the pump part out. Connect a length of aquarium tube to the long straw part and you have a vacuum pump.
If you do find a helper, dont mash the pedal. Slow strokes gets the job done.
Pete
Pressure is best, really, but failing that gravity works fine. Open a bleeder, leave cap off reservoir, and wait until the fluid comes out clear. then move to the next corner and repeat. Don't let the reservoir run dry, obviously.
NOHOME said:Slow strokes gets the job done.
Helper. You and he/she get on he same page as far as call signals ie: PUMP-PUMP-PUMP-HOLD etc.
Obviously start with the caliper furthest away from the master and do not let the level drop so far that you suck air. (Edit: like 02Pilot said above)
In reply to NOHOME :
Unless the master is brand new, never push the pedal down further than it's normal range of travel. There may be a collection of rust and crap stuck to the bottom of the cylinder bore, which can cut the seals.
Modified gravity bleed has you open a bleed screw, then go pump the pedal with very short strokes. Finish by just letting it drip as you watch for bubbles. Then move to the next bleeder and continue. Counter to tradition, I usually start closest to the master and work away. Not sure whether there is a legitimate reason.
Please remember to keep the fluid topped up in the master. Pumping air in the top is always a recipe for pain.
Vote for pressure bleeder. Works great, a little messy the first time but fast and effective. Had to bleed 6 wheels on my 28 foot motorhome and this was the trick.
Gravity bleeder here. Always have great results.
Streetwiseguy said:Unless the master is brand new, never push the pedal down further than it's normal range of travel. There may be a collection of rust and crap stuck to the bottom of the cylinder bore, which can cut the seals.
came in to say this. streetwiseguy is truly streetwise. this is one of the reasons i gravity-bleed exclusively on used masters unless it's a cast-iron MC and i have personally honed and cleaned the bore.
in general, there are two goals for bleeding: one, to get air out; two, to get new fluid in. so i start at the farthest corner from the MC, grab a length of clear tubing that's about 24" long and a snug fit on the nipple of the bleeder, open the bleeder, push the tubing into place, then push the caliper piston (assuming disc brake) in as if doing a pad change (not 100% required, just makes the job go a little quicker). The clear tubing allows you to see air bubbles, and also allows you to see when the clean fluid starts flowing out. there is very little fluid mixing in a gravity bleed, so the transition between dirty and clean is pretty easy to see. crappy sketch to follow.
AngryCorvair said:Streetwiseguy said:Unless the master is brand new, never push the pedal down further than it's normal range of travel. There may be a collection of rust and crap stuck to the bottom of the cylinder bore, which can cut the seals.
came in to say this. streetwiseguy is truly streetwise. this is one of the reasons i gravity-bleed exclusively on used masters unless it's a cast-iron MC and i have personally honed and cleaned the bore.
in general, there are two goals for bleeding: one, to get air out; two, to get new fluid in. so i start at the farthest corner from the MC, grab a length of clear tubing that's about 24" long and a snug fit on the nipple of the bleeder, open the bleeder, push the tubing into place, then push the caliper piston (assuming disc brake) in as if doing a pad change (not 100% required, just makes the job go a little quicker). The clear tubing allows you to see air bubbles, and also allows you to see when the clean fluid starts flowing out. there is very little fluid mixing in a gravity bleed, so the transition between dirty and clean is pretty easy to see. crappy sketch to follow.
I think the "modified gravity" method might be what I go for.
Disc/drum, and the brake pads/shoes have almost zero miles on them (done right before car went offline - including what was then a new MC...), not a lot to push back on to get old stuff out.
Gravity bleeding gives me a better pedal with less hassle than anything else, but it's a really slow way to flush.
As the owner of a '82 320: pull the old fluid out first and gravity feed the clutch first.
Then top off the reservoir and gravity feed the clutch again after the brakes are done. Do not do the push the pedal on the clutch.
The clutch feed line is the high point in the system. It will back flush the old stuff back into your new fluid if you leave it to last.
David
I've never had luck with anything but the pedal stomp.
Vacuum if I'm trying to do a true flush and fill. I inevitably get air past the bleed screws, so I always finish with the one man bleeder. Otherwise, one man bleeder until the fluid doesn't look gross and the fluid stack is non aerated. I usually go furthest from mc in, but some modern abs cars have a specific order.
In reply to AngryCorvair :
It's easy to get streetwise. All you have to do is remember why you got punched in the face each time it happens.
jr02518 said:As the owner of a '82 320: pull the old fluid out first and gravity feed the clutch first.
Then top off the reservoir and gravity feed the clutch again after the brakes are done. Do not do the push the pedal on the clutch.
The clutch feed line is the high point in the system. It will back flush the old stuff back into your new fluid if you leave it to last.
David
As in use a turkey baster or something to pull old fluid out of the MC, refill, GB clutch, etc...?
In reply to Mr. Tanner, best pedal feel is what I'm after...
I'll put another vote in for pressure bleeding if this something you do regularly. I built mine out of a garden sprayer but added an airline fitting to it so I can just turn down my compressors regulator to around 10 PSI and let it do the work. For a cap I used an ATE master cylinder cap for a Mercedes (something like this - https://www.amazon.com/ATE-Brake-Master-Cylinder-Cap/dp/B001G3KXDY) and a few hardware store fittings to put it all together.
Yesterday I did a full flush on my car in under 20 minutes with this setup (car was already in the air with wheels off) by myself. I've never had luck with vacuum bleeding but that was likely crappy equipment more then anything.
Adam
I often combine the two. I'll let it gravity bleed, but I often still have some air... I'm guessing in the little nooks and crannies of the MC. Pumping the pedal actively pushes it through.
Pressure bleeders can introduce microbubbles into the fluid that gives a soft pedal even though the fluid comes out looking good. I've never been happy with the results, even when using the proper shop tools.
If you still have bubbles with a gravity bleed, I think that means you didn't let it drool long enough.
The only proper pressure bleeders have a diaphragm to separate fluid and air. Anything else is just too risky for me. Forget to top up the fluid at the right time? Oops. Use shop air to charge it? Water in the air line? Oops. Shake it up a bit too much? Bubbles, Oops. Jug tips over and you push a bunch of air in? Oops.
Yep, turkey baster or one of the really large syringes my wife can get from the work. These are the really big ones they uses to irrigate wounds.
Refill the reservoir with fresh fluid and then under the car to get to the clutch slave cylinder.
I use vacuum from a running engine. 1 Pull a vacuum line. 2 connect a piece of hose from the vacuum port to the vacuum side of a mity vac collection jar. 3 put another piece of hose over the open bleeder and connect it to the inlet side of the jar. Start the engine and keep the reservoir full. I usually make a larger collection jar as this works extremely fast.
Ha! I like it. Until you look away for a moment and develop brake fluid injection. That would probably be stinky at best.
Keith Tanner said:Ha! I like it. Until you look away for a moment and develop brake fluid injection. That would probably be stinky at best.
Doesn't brake fluid take everything off? New combo brake bleed/ intake valve deposit cleaning method....
"Yep, made it stop and go better all at once."*
*do not try at home; non professionals in an open environment that wound up in the local ICU/ burn unit
Keith Tanner said:Ha! I like it. Until you look away for a moment and develop brake fluid injection. That would probably be stinky at best.
That is one of the reasons that I use a big jar. Something along the lines of a one gallon pickle jar
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