Can Master Cylinder be bled with Pressure Bleeder?

[Chuck]

I've had great difficulty putting a "bench bled" master cylinder on my 88 Windcruiser, since it is extremely difficult to get the nuts to line up when putting on.  I emptied the rear well twice trying to do this, and to take it back off and preprime it again seems useless.  On top of that, because of limited room you have to mount from underneath, and lying on your back with brake fluid streaming down your arm into your shirt and face is not my idea of something you want to fight with all day.

I have a double whammy going on here with the brake system, because I discovered the leak in the master cylinder when I got a severed brake line on the rear axle.  The air springs have a leak and once they seeped all of the air out, the chassis came down and an attached air valve severed the line.  I have since re-routed a new line painfully and now wish that I had a pit to work out of. 

Does anyone have any experience with a pressure bleeder, and if so, will this remove the air pockets out of the master cylinder?  I've tried a vaccum type from the wheel cylinders only to find that the bleeders should be stainless or have a smooth surface, elsewise air seeps in around the nipples putting confusing bubbles in the vaccum line.  Anyone have any good tactics for getting all of the air out?

Thanks in advance for your input.

Chuck

[DanielTBolger]

they make a bleeder kit with two hose's the you can bolt the master cly   and slowly hand pump the  peddle why look down  the top of the master cly keep the hose's below the brake fluid wait till bubble stop come out then have some one hold peddle to the floor and put the line back on

[Froggy1936]

A pressure bleeder (one that replaces the M/C cap or cover and uses fluid under pressure) is the very best way to bleed any hydraulic system brakes or clutch and this will also bleed M/C .  But if you have bench bled the M/C emptying the reservoir will not put air in the operating system of the M/C refilling after mounting will remove any remaining air in M/C. But the air in the lines (from being removed will have to be bled out.  A good tip to stop the armpit bath with brake fluid, fuel or anti freeze is to wrap your arm with a large rag and hold it in place with a rubber band  if you are quick enough you will catch most of the fluids.  Frank

[Chuck]

Thanks guys for your input - Froggy I believe you answered my question.  I was mainly concerned that my mc had filled back up with air during the line struggle but per your input it sounds as if it didn't.  However, for my own sanity and since it will bleed the mc, I will probably still seek a pressure bleeder.  Maybe I can borrow one, sheesh they are kind of proud of them aren't they?  If I get shut down by my own thriftyness I'll go buy some stainless bleeders and go back to the vaccum type. 

Happy Camping!

[Froggy1936]

One other thing, They make a bleeder screw with a spring loaded check ball that allows 1 person to bleed the brakes ( you just leave the bleeder unscrewed 1 full turn and pump the pedal very slowly the check ball closes the system after fluid is expelled) make sure you keep the  M C full and only do 1 wheel at a time  Frank

[Dunnohow2]

I have done two things which have helped and saved time and brake fluid armpit rinse. But before starting any brake work, I spray lashings of penetrating fluid - not WD40 which is not penetrating fluid - all over the wheel cylinder bleed valve nipples.
Method
1 Cut an access hole in the cab floor above the master cylinder. 
It was fiddly because I didn't know the floor is two metal sheets sandwiching some type of foam insulation.  After trying various tools, I found the reciprocating saw with a small blade worked best.  There are a few square metal tubes embedded in the layers which you van feel through the saw.  I made a lid and with a piece of piano hinge and pop rivets and turn button catch all was on view and easily accessible.

2 Make a pressure bleeder
I used:
2 angled metal tyre air valves, the sort which are attached to the wheel rim with nuts, not the rubber pull through type.  The cheapest I found were from a motor cycle dealer  C$8 pair.
1 length of clear plastic pipe id large enough to fit over the air valve stems  C$5
1 one gallon garden pump up spray bottle that incorporates a hand pump plunger in the bottle top and a spray hose outlet C$8
1 plastic tee piece to fit the tubing C$2
1 compressed air pressure regulator with gauge 0-30 psi  C$6
Assorted pipe fittings to connect the sprayer outlet thread to the bleeder pipe and into the spray bottle.  I used a male and female brass fitting that had the right size of hose barbs to fit tightly into the piping and screw together through the bottle wall.
1 old reservoir top with brake fluid resistible rubber gasket - This is not really necessary as the air valves can be put on the existing top because the top is vented but I had one.

Total cost was about C$35.
Build notes
Drill two holes one each on a flat face in the M/C cap and gasket; one above each reservoir of a size to bolt the air valves through. NOTE ensure the hole locations do not prevent the cap retaining clip from clipping into place.
Attach short lengths of pipe to the underside of each valve to hang into each reservoir and prevent filling to the brim.
Attach piping to the top of each valve and connect to the arms of the tee fitting
Attach a longish length of piping from the tee to the spray bottle's outlet thread - may need some teflon tape etc. to match threads.
Drill a hole on the flatest surface at the top of the sprayer bottle and fix the air regulator and gauge.  I had to use rubber gaskets made from old bike tubes and penny washers to make the surface as flat as possible. Most cheap sprayers are all curves.
Make sure that the tube to the M/C is extended into the sprayer bottle to about 1/8" from the bottom.
Gently (minimizing air bubbles) pour a couple of litres of clean brake fluid into the sprayer and tighten the lid with the plunger.
Locate the spray bottle on the ground inside the right front wheel well below the M/C. Clip the reservoir cap in place and pump the plunger several strokes and the fluid will flow up through the piping into the two reservoirs.
Once the pressure rises, watch for any leaks and tighten where necessary.
Starting at the rear right wheel (farthest from the M/C gently loosen the bleed valve nipple.  Once it is loosened, attach a piece of clear plastic tube with id to fit the nipple and hang the pipe into a clear glass or plastic jar with an inch or so of brake fluid added to it.  I use mason jars because the lids are easy to punch holes in. I make three holes in the lid - One in the middle for the nipple tube to go through enough to be below the surface of the brake fluid in the jar.  The pipe can be held in place with a small rectangle (1" x 2") of flexible plastic e.g. cut from say a coffee tin or butter tub lid, punch two holes near the narrow edges and large enough for the pipe to pass through.  Pushing the pipe through one side and bending the plastic rectangle in the middle before passing the tube back out through the other hole will make a movable friction lock to hold the pipe in place on the underside of the lid. 
Then punch two  holes in the lid towards the edge and opposite one another.  A suitable length of wire - I use a 15" strand of 14/2 copper house wire which can be poked down through one hole and up out of the other to make a hanging device which can be attached to something nearby.  I have learned that a jar on the floor will always fall over and spill brake fluid.
With the jar lid in place, the pipe extended into the fluid and the jar wired in place, undo the bleed nipple and allow the old fluid and air bubbles to exit from the cylinder into the jar.  When the fluid runs clean, gently retighten the nipple, pull the pipe off the nipple and unwire the jar.
Empty enough of the old fluid out of the jar - to leave an inch in it - into an empty brake fluid jug which can be recapped and disposed of properly.
Check the fluid in the spray bleeder, topping up as needed, repump to 20+ psi and continue the bleed process in sequence, left rear, right front, left front attending to old and new brake fluid as necessary. 
When done, release the air pressure in the sprayer and because the sprayer is below the M/C, the reservoir cap can be removed and the clean fluid in the pipe can flow back into the sprayer without splashing brake fluid everywhere.
When one, check the reservoir levels via the access hole and top up as necessary.
I rebleed the brakes after a few weeks to remove any unreleased air which gets forced through the system and collects at the nipples..
If the M/C is being replaced, I fill and bleed it on the bench before fitting.

The access lid in the cab floor is alongside the driver seat and is readily accessible to keep an eye on the brake fluid levels in each reservoir.

I hope this helps.  It took longer to type than to make.
jenni.