Filling/Bleeding a Dry Disc/Drum System

[MoparGuy68]

I’ve completed my new disc/drum hydraulic system on my 1971 Super Bee.

Rebuilt: booster, master cylinder (stainless steel sleeved), calipers and wheel cylinders (stainless steel sleeved).

New: OEM 71 brass proportioning valve and metering valve. All OEM hard lines (not stainless steel). OEM hoses. OEM brass tee block.

The entire system is completely dry. I need to fill/bleed it myself, solo, with no help from another person, as I don’t have anyone available to help.

I have a pneumatic bleeder kit, that hooks up to an air compressor, that I got from harbor freight (months ago). My compressor is a 6 gallon pancake with max pressure 150 psi. Bleeder kit says to use with pressure range of 90 to 120 psi.

Don’t know how well the bleeder kit will work with a 6 gallon tank pressurized to only 120 psi.. I know I’ll have to bleed till pressure drops to 90, then run compressor back up to 120, and repeat. Don’t think I’ll be able to use the filler bottle, as it’s designed to mount on a modern reservoir that has a round filler hole with screw on cap.

Do you guys think I should attempt to bleed the master cylinder, via brake pedal, or while off the car first? Or try to bleed the entire system using the compressor, without bleeding the master (in a traditional manner) first?

Lastly, being that the entire system is OEM, I was thinking I should use DOT 3 fluid. The rebuilt master, calipers and wheel cylinders were previously using DOT 3 before the rebuild. They may have been tested with DOT 3, by Karps in CA, before being shipped to me. So, maybe I shouldn’t experiment with using a newer synthetic fluid..

 

[1 Wild R/T]

For a dry system I use an oil can, throughly cleaned, take it apart & get any oil out... Then run a little brake fluid through it to be safe... Then fill it with brake fluid....

With the lid sitting on the M/C, I start at the right rear, use a rubber hose to attach the oil can to the bleeder (open the bleeder a turn) pump maybe 15 squirts of fluid, the close the bleeder... Move to the other side, this time maybe 30-35 squirts then check to see if your getting fluid to the M/C, I like to push enough fluid through the bleeders to get at least 1/2" of fluid in the bottom of the M/C.. Remember to put the cover back on..

Next go to the RF & repeat, then go to the LF... After pushing fluid through the whole system you'll need to pump the pedal a few times to seat the calipers since they were probably fully retracted...


This method has always worked for me, been doing it that way on restos for 30 years... But a couple years ago someone I explained it to on the forum tried it & said it didn't work for them.... No idea why...

 

[MoparGuy68]

For a dry system I use an oil can, throughly cleaned, take it apart & get any oil out... Then run a little brake fluid through it to be safe... Then fill it with brake fluid....

View attachment 1282028

With the lid sitting on the M/C, I start at the right rear, use a rubber hose to attach the oil can to the bleeder (open the bleeder a turn) pump maybe 15 squirts of fluid, the close the bleeder... Move to the other side, this time maybe 30-35 squirts then check to see if your getting fluid to the M/C, I like to push enough fluid through the bleeders to get at least 1/2" of fluid in the bottom of the M/C.. Remember to put the cover back on..

Next go to the RF & repeat, then go to the LF... After pushing fluid through the whole system you'll need to pump the pedal a few times to seat the calipers since they were probably fully retracted...


This method has always worked for me, been doing it that way on restos for 30 years... But a couple years ago someone I explained it to on the forum tried it & said it didn't work for them.... No idea why...

You are describing a pressure fill/bleed method. You have the master lid unclamped, and laying on top of the master in a way that allows air to escape, but also block streams of fluid from shooting up out of the master, when pumping with the oil can?

 

[HEMI-ITIS]

Might try to bench bleed the master before install.After install fill master and open all the bleeders to gravity bleed.Have a catch can at each wheel to catch the fluid.

 

[MoparGuy68]

There is the gravity fill/bleed method also.. I have saved four empty plastic bottles over the months. I could get some clear hose to run from each bleed screw into each bottle.

Could try the gravity method first, then the vacuum/compressor, if the gravity alone doesn’t work.. maybe gravity to fill, and vacuum for final air purge..

 

[1 Wild R/T]

You are describing a pressure fill/bleed method. You have the master lid unclamped, and laying on top of the master in a way that allows air to escape, but also block streams of fluid from shooting up out of the master, when pumping with the oil can?

Typically pressure bleeding forces fluid from the M/C down to the W/C's but that means you have to force the air down & out... Air tries to rise, why fight it, let it exit out the top... Yes the cover is left in place to prevent fluid from making a mess

 

[MoparGuy68]

Might try to bench bleed the master before install.After install fill master and open all the bleeders to gravity bleed.Have a catch can at each wheel to catch the fluid.

The problem with bench bleed is I don’t have a bench vise. No way hold the master securely to pump it while off the car..

 

[MoparGuy68]

Typically pressure bleeding forces fluid from the M/C down to the W/C's but that means you have to force the air down & out... Air tries to rise, why fight it, let it exit out the top... Yes the cover is left in place to prevent fluid from making a mess

As you are pumping fluid into the bleeder screw, can air be pulled into the caliper/wheel cylinder through the bleeder screw threads? When the screw is open the thread area is not air tight.

 

[1 Wild R/T]

If you want to bench bleed it can actually be done on the car, bench bleed implies it's done on a bench but thats not necessarily true... you can loop the fluid back to the reservoir & use the pedal to push fluid..
Or you can use a syringe to push fluid...



kinda like using an oil can & pushing fluid through the whole system...

 

[1 Wild R/T]

As you are pumping fluid into the bleeder screw, can air be pulled into the caliper/wheel cylinder through the bleeder screw threads? When the screw is open the thread area is not air tight.

Yeah, which is what happens when you try to vacuum bleed a brake system.. But since the oil can puts the system under slight pressure you more likely to see fluid seeping than air getting drawn in..

 

[pro451bee]

When all parts are mostly new and work properly , open all bleeders at the wheels , fill master cyl mounted to car , just crack open the lines at master cyl. till fluid drains freely , close lines re fill master and wait for fluid at wheels steady stream , gentle tap at calipers with small hammer while bleeding helps loosen bubbles . Dont let master go dry. Close all bleeders and test brakes for firmness several slow pumps , not all the way to the floor at first to the move out pistons and loosen air bubbles , check /fill master again , go around car again and gravity bleed one at a time . This is all I ever do and allways works .

 

[steve340]

You don't need to bench bleed if you use the vacuum bleeder in your picture.
Just suck it through the bleed nipples.
I always do mine that way - very little mess and you can do it by yourself.

 

[MoparGuy68]

You don't need to bench bleed if you use the vacuum bleeder in your picture.
Just suck it through the bleed nipples.
I always do mine that way - very little mess and you can do it by yourself.

Do you mean to only use the vacuum bleeder to bleed the master cylinder while it is mounted on the car? By holding the rubber fitting, on the end of the hose, up to the master threaded outlets? Maybe my little compressor could handle that.

A little while ago I watched a video of a guy “attempting” to fill/bleed a completely dry system, like I have with the same vacuum bleeder I have. He had a much bigger compressor than I do, with a large holding tank. He was having to run the compressor A LOT to try to get all the air out of his system. It took him a long time.. Judging by what he went through with a large compressor, my 6 gallon pancake compressor isn’t going to handle the job..

 

[steve340]

No connect all the pipes and do all the necessary adjustments.
Fill the system and suck it through the bleed nipples at the wheels.
You do not need a lot of air but just go easy if you loose air the vacuum will stop.
If you have pipe leaks or poor adjustment you will have problems.
Done properly this way is quick and clean.

 

[MoparGuy68]

No connect all the pipes and do all the necessary adjustments.
Fill the system and suck it through the bleed nipples at the wheels.
You do not need a lot of air but just go easy if you loose air the vacuum will stop.
If you have pipe leaks or poor adjustment you will have problems.
Done properly this way is quick and clean.

I’m favoring giving this technique a try, because I already have the vacuum device and I don’t think I can obtain an oil can pump or syringe today (would have to wait until next weekend for either of those). I would think that if this technique ends up failing I could always try the other ones next weekend.

What about when applying vacuum to the bleeder nipple? Air being sucked past the nipple’s threads back into the wheel cylinder or caliper. I suppose I could follow up the vacuum technique with a final brake pedal pressure bleed, with a clear hose run from the nipple into a bottle, to purge any air that gets sucked in past the threads.

 

[steve340]

I heard you can use a little teflon tape on the threads but I never have. With the vacuum applied air will only come out - when you fill etc close the nipple. I coat the threaded part with anti-seize.
I pay no notice to the bubbles in the tube - but I only crack the bleeder enough to allow fluid to pass. You do need a good fitting hose on the bleed nipple.
I can bleed a whole car with 600 ml of fluid doing it this way.
Like I said if you have got pipe leaks or something wrong you may have trouble - but no matter what method you use you were heading that way.

 

[MoparGuy68]

I decided not to attempt the fill/bleed today, was still sore and worn out from Saturday and didn’t sleep well laying in bed last night, pondering how to fill and bleed.

I spent most of Saturday installing the calipers, pads, pins, springs and hoses. Had to do the passenger side three times. Forgot the anti-rattle spring the first time. Second time because I installed both outer pads on that caliper, which I discovered when attempting to install an inner pad in the driver caliper outer position. Upon casual inspection, before I started the work, I thought all four pads were identical. Didn’t examine them closely enough..

Next weekend I’ll continue the work..

 

[MoparGuy68]

Going to attempt to fill/bleed today.

After reading my service manual this morning, it states if attempting a pressure bleed (which includes the vacuum pressure method) the metering valve (for front discs) needs to be held open. That valve will shut when system pressure is between 3 to 135 psi, cutting off fluid flow to the calipers. The compressor will be operating in that range 90 to 120 psi, so that valve will cut off flow, it won’t work..

I don’t have the special tool, shown in the manual, to hold the valve open. The tool is part number C-4121. I have the metering valve shown in bottom half of the photo.

So, it looks like I’m going to have to use the gravity and petal bleed methods for the front caliper part of the system.

I can’t find any specifications for the fluid capacity of the brake system for 1971 or any of these cars.

i’m guessing I’m going to have to buy at least 24 ounces of brake fluid to fill and bleed the whole system. Maybe I will need 36 ounces if I run into problems.

 

[Don Frelier]

I only use synthetic in all my vehicles.
Dot3 is highly corrosive and absorbs moisture.
We have a lot of moisture around here.

 

[MoparGuy68]

I only use synthetic in all my vehicles.
Dot3 is highly corrosive and absorbs moisture.
We have a lot of moisture around here.

I’m in AZ, we have a lack of moisture here.

What synthetic fluid type do you use? Do you have front discs and the factory brass valves with the metering valve like I have?

Here is a 2013 article stating that DOT 5.1 can be used in place of, or even mixed with DOT 3 & 4. DOT 5 cannot be mixed with 3 or 4, or used in a system that hasn’t been completely flushed of all 3 or 4 fluid.

https://www.hemmings.com/stories/20...ferent-about-them-and-why-should-you-care/amp

Even though my master cylinder, calipers and wheel cylinders were rebuilt, Karps may have put DOT 3 in them to test before shipping them out to me. There may be traces of 3 inside all of them..