Power bleeding

[Rick Dorion]

I have all new components on my 68 - MC (bench bled), lines, calipers, MC, etc. I am using a Motive power bleeder but can't get a firm pedal and have no leaks.

I've been using 10# pressure - is this enough? I see micro-bubbles when I crack the bleeder screws. I've tapped with a hammer to dislodge air bubbles too.

What am I missing? TIA.

[JEFFTATE]

The Motive Bleeder , does it push the fluid through or pull it through ??
I had trouble with my brakes recently and found a leak on the front circuit that was almost undetectable.
There was no fluid dampness anywhere.
But the system was pulling air back in through the leak point.
I kept getting air in the system but couldn't see a noticable fluid leak anywhere.

Of course , I was doing a vacuum bleeding method.

[Rick Dorion]

It pushes, Jeff.

[noobwrench]

Crank the pressure up a little and open all 4 bleeders at once, its worth a shot.

Also is the pedal spongey or does it sink slowly?

[JEFFTATE]

How much fluid have you pushed through the system ??
A cup ?
A pint ?
A quart ??
Maybe you just haven't gotten all the air out yet ??

Are you getting air in from around the bleeder screws ??
I always put some Teflon tape on the threads of the bleeder screws to prevent air from getting back in that way.
Of course , you are using a pressure bleeder , and that makes things different.

Hmmm ...........................

[BRIAN]

Not going to say that is doesn't work but that Motive deal can get messy.
When you say you are getting bubbles do you mean the fluid is shooting out of the bleeder under pressure? Are you bleeding with brake pedal depressed or in up position? Going by memory doesn't Motive state 15-20???


You could always try a different color fluid to detect full flush and flow.
Good luck

[Rick Dorion]

The pedal is firming up but isn't 'hard'.

I use the Motive dry, ie. only as a pressure source. Less messy and cleaner but more a pain to constanly refill the MC.

Good point on not having pushed alot of fluid through. I see very tiny bubbles so I'll keep trying. Maybe I underestimated the amount of air in a dry system and the 'cling on' effect?

I'm bleeding with the pedal 'up'.

I am solo on this, hence the use of the Motive.

[JRouche]

I think you are on the right track. A dry system can be hard to bleed.

I had a stupid (on my part) bleeding adventure where no matter what I was still getting a low pedal. So I made up a spare cap rig for my MC and put 15PSI of air to the top of the MC. Man, it blew out alot of air pockets. Maybe a lil more pressure wont hurt.

Oh, and on another thread I read there was an issue with the rear parking brake not being adjusted correctly. So the rear cylinders were having to move to far to take up the distance. A thought. JR

[MonzaRacer]

OK first of all you have mostly filled system, place lots of rags under master cylinder and around, loosen the lines at the master cylinder so lines are loose but dont remove nut, have partner push pedal to floor slowly or you make mess and get fluid everywhere and its loves to eat paint.
Do it 3 time for each side, then start this way, if its disc start on right rear, and have partner pump pedal not fast just down, up, down, up, down, up,down and hold it, they say ready, you open bleeder, 1/4 turn should open it fine, close before done running.
Do it 3 times at each wheel.
Also make sure it brand new fluid from sealed container. Now pump it up 3 times, and hold, try to feel it sinking if not and fluid was clear of big bubbles your good to go, if it has new pads and rotors till you drive it few feet and get pads settled and all it may feel spongy. I have done brakes for over 20 yrs and they still scare me on first few stops.
Also on new pads seem to have a rough surface but it was ground and has valleys and peaks and may not make perfect contact till rubbed few time by rotors.
AS for bleeding I love my Phoeneix Injector, for reverse bleeding, if changing master I reverse bleed up to the master cylinder, then bench bleed with my Phoenix Injector.