Clutch/Brake Bleeding

A seemingly simple process that I seem to only get right 50% of the time.

First question. I've been running with the knowledge that when bleeding brakes and clutch you never want the pedal to go down all the way when holding to crack the bleeder.

Right? Wrong? Doesn't matter?

Best thing I have ever done is buy a pressure bleeder.

It depends, new m/cylinder no problem, all the way down. However, some prefer not to push to the floor on older high mileage m/cylinders. The concern is the buildup of crud/rust in the m/cylinder bore may damage the cup seals.

On bikes with hydraulic brakes and on cheap atv's with really cheap hydraulic brakes, i usually apply brake pressure lightly with the bleeder open, then before stopping applying pressure, i close the bleeder. This sucks the fluid down to the caliper. A few few rounds of it and usually get solid results.  Crack the bleeder again, press brakes again slowly, see if i get air bubbles out of the bleeder or clean fluid, close bleeder and release pressure so it sucks fluid in, not air. Something like that. 
 

also yes, the pressure bleeder setups are sweet. 

Let gravity do as much as possible, first.  Make sure you never let the fluid go too far down in the reservoir. A bunch of one inch pumps will sometimes finish the gravity bleed.  Let the pedal come up slowly so you don't create a vacuum that can pull air past the seals.  Always close the bleeder before the pedal pressure drops all the way.  On an old master cylinder, don't stroke the pedal farther than it's normal travel, as there may be junk in the bottom of the bore that can damage the seals.

Clutches can be a real bear, because there is often too much vertical in not enough distance.  I use a rubber tipped blow gun hooked to my pressure pleeder to push fluid backwards from the clutch slave on particularly tough ones.

Pressure bleeders are great.  Vacuum bleeders, not so much.

Thanks for the tips - the methods sound very much like what I do. 

I didn't know the rationale behind not pressing all the way down. Makes sense. 

I'm going to give it another shot but considering it's always a struggle, I think a pressure bleeder is in my future. 

+1 on the pressure bleeder. I can flush a car in 20 minutes hardly even trying. I bought one that did not have adapters to many of my cars (it would do one). 80 cents at the pick and pull got me a "spare" reservoir cap. Drill a hole in that, extra pieces of rubber gasket material, and sometimes a little glue to plug the cap vent path, and now I have adapters for all the cars at just a few bucks per adapter. I made quick releases, just for fun, but setting up with regular barb fittings would work just as well and all the parts for that are at the hardware store.

For clutches I work from the slave cylinder, never touching the pedal. I crack the bleeder and push in the piston, then close the bleeder. The spring in the slave cylinder pulls the fluid out of the master cylinder. About 4 times like that and you have fluid come out of the bleeder when you push in the slave piston. Once you have that, close the bleeder and you are done.

You can make a pressure bleeder from a spare master cylinder cap and a snap-in valve stem.  I would like to say you drill a 27/64ths hole in the cap for the valve stem.

When playing musical calipers in the one RX-7 I had a bear of a time trying to bleed the system.  Could not get the air out of the master, which meant could not push fluid through the system.  I do have a Mityvac bleeder system, and I rerouted its hoses to turn it into a pressure bleeder to force fluid up from the calipers to the master.  Will want to put Teflon tape on the bleeder screw to keep from making too much of a mess.  Pushes all the air up and out the compensation port in the master.  Took less than ten minutes to go from all air to rock hard pedal.

Pressure bleeder on order. 

AxeHealey said:

Pressure bleeder on order. 

Good choice.  The cap to fit whatever is best made from an extra scrap one.  Normally 10 PSI is enough, more can just blow off lines in the bleeder.  And some cars can be a real pain, only a helper on the pedal works.  Worst one I ever did was the GMC motorhome.  Four rear wheels and 20 foot long lines.  Had to make a fixture to hook it up and went thru a gallon of fliud.  But in the end it worked.

I'm not a fan of pressure bleeders. I can never get a really good pedal out of the Motive with the correct adapters on a Miata. I think they can introduce microbubbles into the fluid. Great for a flat rate production shop, but I use a gravity bleed on my cars.

Welp. Hopefully it works better for me than it has for you since that's the one I bought...

I cracked the bleeder on the slave yesterday with the cap off of the master and let it sit for 20 min yesterday and nothing came through.

In reply to Keith Tanner :

The one I use on the Rio is fantastic. 

In reply to Keith Tanner :

I gave my motive one away. It pissed me off one too many times. 

Whatever approach you use, speed-bleeders are great insurance, too. The threads on the bleeder screw can get sloppy over time and let air in when cracked open, and I am very sure this is why I could never get a good bleed on my Elise. Since I needed new screws, I went with the speed-bleeders. Even if the check valve does nothing, the fresh threads held a noticeably better seal when cracked open (my old screws would burble out some brake fluid near the wrench as well as the tubing). But, even with good threads, don't open the screw any more than you have to for this reason. 

For my E91, there was air in the ABS module from when the indy I bought it from swapped out the module and didn't bleed it correctly. The proper fix is to get whatever computer tool your car needs and go through an ABS diagnostic module to cycle the valves and move the air out. The shade-tree way is to just get some good ABS engagements. Gravel is great, but a wet road works, too. After doing a few ABS stops, I re-bled the brakes. The pedal was so much firmer it actually tripped a brake pressure higher-than-expected fault until it re-learned the new pressure. Even with an original ABS module, I wouldn't rule out air in it being possible. 

Patrick said:

In reply to Keith Tanner :

I gave my motive one away. It pissed me off one too many times. 

in all fairness mines not a motive brand one. For clutches I usually just gravity bleed. I had an 89 C1500 V6 that would not bleed with the pedal. Graviy bled and it worked flawlessly for the next 2 years and 30k miles before I sold it.

AxeHealey said:

Welp. Hopefully it works better for me than it has for you since that's the one I bought...

 

I cracked the bleeder on the slave yesterday with the cap off of the master and let it sit for 20 min yesterday and nothing came through.

Reverse pressure bleeders feel like cheating.

I hear you, Pete. I may be going your route. 

I left the bleeder open and the reservoir cap off all afternoon in an attempt to gravity bleed but not one drip came out.

EDIT: I have gotten the suggestion about speed bleeders and have considered ordering them for all of the vehicles I may do brakes on because they sound awesome. 

I got speed bleeders for something and feel like at this point i will buy them for everything that's getting brake hydraulic work. 

Uh my Phoenix worked miracles on the clutch in my 91 gmt400 5spd....cheating or otherwise...done is done....this tool also ranks as best $$$ spent on garageness

One of these: 

Plus, one of these (bottle with a check valve): 

Pete. (l33t FS) said:

AxeHealey said:

Welp. Hopefully it works better for me than it has for you since that's the one I bought...

 

I cracked the bleeder on the slave yesterday with the cap off of the master and let it sit for 20 min yesterday and nothing came through.

Reverse pressure bleeders feel like cheating.

But sometimes cheaters win.

Streetwiseguy said:

Pete. (l33t FS) said:

AxeHealey said:

Welp. Hopefully it works better for me than it has for you since that's the one I bought...

 

I cracked the bleeder on the slave yesterday with the cap off of the master and let it sit for 20 min yesterday and nothing came through.

Reverse pressure bleeders feel like cheating.

But sometimes cheaters win.

Cheaters never perspire.

hunter47 said:

One of these: 

 

Plus, one of these (bottle with a check valve): 

 

Fill with fluid, connect the red fitting and hose (which goes to the tube) to the bleeder, apply steady pressure to the black fitting.   Reverse pressure bleeder.

My Mityvac setup came with a bottle like that, and I could stick a hose on the vacuum vent to make a pressure pump.  No check valve in the bottle.