# New brakes issue



## Tim68 (Dec 1, 2019)

I have just completed the disc brake conversion for all four wheels. I have also replaced all the brake lines and master cylinder. I bench bled the master cylinder and bled the lines. Had a couple leaks that have been resolved. Not getting any air when bleeding but still petal goes to the floor. It will pump up but slowly goes to the floor.
seems like there is still air in the lines but after bleeding them numerous times and not seeing any more air.
Will the proportioning valve cause this issue? That’s the only thing I have not replaced.
I have bled braked numerous times before but have not had this hard or time to get the petal pressure.
any help?


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## RMTZ67 (Mar 12, 2011)

Tim68 said:


> I have just completed the disc brake conversion for all four wheels. I have also replaced all the brake lines and master cylinder. I bench bled the master cylinder and bled the lines. Had a couple leaks that have been resolved. Not getting any air when bleeding but still petal goes to the floor. It will pump up but slowly goes to the floor.
> seems like there is still air in the lines but after bleeding them numerous times and not seeing any more air.
> Will the proportioning valve cause this issue? That’s the only thing I have not replaced.
> I have bled braked numerous times before but have not had this hard or time to get the petal pressure.
> any help?


Not sure if your p valve will suffice for 4 wheel disc, did you have disc up front before? Are you using your old rod and brake booster? If the proportion valve is stuck to the front or rear, I would think you would get pedal either front or rear.


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## Tim68 (Dec 1, 2019)

RMTZ67 said:


> Not sure if your p valve will suffice for 4 wheel disc, did you have disc up front before? Are you using your old rod and brake booster? If the proportion valve is stuck to the front or rear, I would think you would get pedal either front or rear.


I had all four drum. I replaced the master cylinder only after numerous attempts to get the proper petal. 
i am getting fluid at all four calibers. I can’t tell if there is any more front to rear.


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## RMTZ67 (Mar 12, 2011)

Tim68 said:


> I had all four drum. I replaced the master cylinder only after numerous attempts to get the proper petal.
> i am getting fluid at all four calibers. I can’t tell if there is any more front to rear.


Do you even have a proportioning valve or a a distribution block on the frame? Here is my set up from 4 drum to 4 disc. P valve on top.


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## Tim68 (Dec 1, 2019)

RMTZ67 said:


> Do you even have a proportioning valve or a a distribution block on the frame? Here is my set up from 4 drum to 4 disc. P valve on top.


I looked on line and found what I have is a distribution block. It’s mounted on the frame below the master cylinder 








1967 Pontiac Buick Oldsmobile A-Body, 1968-69 All GM A-Body, Disc or Drum Distribution Block


1967 Pontiac Buick Oldsmobile A-Body, 1968-69 All GM A-Body, Disc or Drum Distribution Block




www.inlinetube.com


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## RMTZ67 (Mar 12, 2011)

Don't ask me how I know but, check your calipers to make sure the bleeders are on top. Believe it or not they fit upside down. If I am not mistaken the proportioning valve has a pin that slides back and forth so if you loose brakes you will not loose both front and back. Not sure about a distribution block. I could not get the front to get a hard pedal during the bleed stage I finally found the issue. One caliper upside down.


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## Tim68 (Dec 1, 2019)

RMTZ67 said:


> Don't ask me how I know but, check your calipers to make sure the bleeders are on top. Believe it or not they fit upside down. If I am not mistaken the proportioning valve has a pin that slides back and forth so if you loose brakes you will not loose both front and back. Not sure about a distribution block. I could not get the front to get a hard pedal during the bleed stage I finally found the issue. One caliper upside down.


I checked and the calipers are correct.
Thanks


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## Bopman (7 mo ago)

RMTZ67 said:


> Don't ask me how I know but, check your calipers to make sure the bleeders are on top. Believe it or not they fit upside down. If I am not mistaken the proportioning valve has a pin that slides back and forth so if you loose brakes you will not loose both front and back. Not sure about a distribution block. I could not get the front to get a hard pedal during the bleed stage I finally found the issue. One caliper upside down.


My son found that out the hard way too ! 😊


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## Bopman (7 mo ago)

Tim68 said:


> I have just completed the disc brake conversion for all four wheels. I have also replaced all the brake lines and master cylinder. I bench bled the master cylinder and bled the lines. Had a couple leaks that have been resolved. Not getting any air when bleeding but still petal goes to the floor. It will pump up but slowly goes to the floor.
> seems like there is still air in the lines but after bleeding them numerous times and not seeing any more air.
> Will the proportioning valve cause this issue? That’s the only thing I have not replaced.
> I have bled braked numerous times before but have not had this hard or time to get the petal pressure.
> any help?


Could it be bypassing inside master cylinder ?


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## PontiacJim (Dec 29, 2012)

Is this a complete aftermarket "kit" or are you mix/matching parts of your own accord?


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## lust4speed (Jul 5, 2019)

Sounds like you are not talking about a spongy pedal but more like a firm pedal that slowly travels to the floor? If you have a relatively hard pedal that slowly drops away then you are loosing fluid. If there are no puddles on the floor, then the fluid would be leaking past the seals inside the master cylinder. You wouldn't be the first one to receive a garbage master cylinder right out of the box.


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## LATECH (Jul 18, 2018)

Hard to tell if the "distribution block" is anything more than a safety valve.It must be a safety valve as it has the switch for the Brake warning light.
Since it says it works for either disc or drum systems, it likely doesnt have any residual pressure valves or a hold off valve for the rear brakes like a disc/drum setup would have.
I tend to lean towards the master, but without knowing whether or not you have residual pressure valves in the master for a disc/disc system its a crap shoot find the trouble.
Also mster cylinder bore size will affect pedal travel.Larger diameter master cylinders move more fluid as it "sweeps" (applying brakes) and can move a disc piston further giving a feedback at the brake pedal that makes the pedal feel higher .
So, Master cylinder bore and residual pressure valves are the question. Do you have and what size.
Also which calipers are you using.
The brake system has to be balanced between the master cylinder bore size and the caliper piston size.
The master has to be able to move enough fluid to move all those pistons , be it 4 ,6 , or 8. 
If the caliers have too large of a piston area and the master has a small bore, it likely wont move enough fluid to apply the brake, and may require additional application of the brake pedal to move the pistons far enough to apply the brakes


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## RMTZ67 (Mar 12, 2011)

Without knowing your whole set up as PJ was asking, kinda just guessing. Do you have a brake booster?


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## Tim68 (Dec 1, 2019)

PontiacJim said:


> Is this a complete aftermarket "kit" or are you mix/matching parts of your own accord?


CCP front brakes
rear from Inline as well as the brake lines
master cylinder from NAPA


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## Tim68 (Dec 1, 2019)

RMTZ67 said:


> Without knowing your whole set up as PJ was asking, kinda just guessing. Do you have a brake booster?


It is a power brake system


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## Tim68 (Dec 1, 2019)

Tim68 said:


> It is a power brake system


One note:
The brakes worked fine prior to the change. The master cylinder had no issues. I changed it after numerous attempts to bleed the system As a trouble shooting measure. No change after changing the master cylinde.


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## RMTZ67 (Mar 12, 2011)

Tim68 said:


> One note:
> The brakes worked fine prior to the change. The master cylinder had no issues. I changed it after numerous attempts to bleed the system As a trouble shooting measure. No change after changing the master cylinde.


Do you get a hard pedal after several pumps or does it just go to the floor every time. can you take a picture of your upper master cylinder area. your vacuum to your booster is hooked up and no leaks? Also wondering of the length of the rod between master and booster..if its to short because of the master change.


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## Mine'sa66 (Oct 30, 2019)

So you had power 4 wheel drum brakes to start? What did you buy for a master?
Could be the wrong one....also you describe symptoms of a poorly bled master.
Also, you should change that prop valve to a more modern one made for disc brakes. 
@LATECH has asked most of the same questions I see now lol


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## Tim68 (Dec 1, 2019)

RMTZ67 said:


> Do you get a hard pedal after several pumps or does it just go to the floor every time. can you take a picture of your upper master cylinder area. your vacuum to your booster is hooked up and no leaks? Also wondering of the length of the rod between master and booster..if its to short because of the master change.


The first pic has the old master the sec one is the replacement.


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## Tim68 (Dec 1, 2019)

RMTZ67 said:


> Do you get a hard pedal after several pumps or does it just go to the floor every time. can you take a picture of your upper master cylinder area. your vacuum to your booster is hooked up and no leaks? Also wondering of the length of the rod between master and booster..if its to short because of the master change.


After a couple pumps the petal firms up. Wait a few seconds and try again, goes to the floor.


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## LATECH (Jul 18, 2018)

The first pic looks like a Disc/Disc master
Pic 2 is definitely a disc/drum master. 
Show us a better picture of master in Pic 1 please


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## Mine'sa66 (Oct 30, 2019)

Tim68 said:


> After a couple pumps the petal firms up. Wait a few seconds and try again, goes to the floor.


If you pump the pedal up, can you still overpower it to the floor or do you have to wait before it will fade?


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## Tim68 (Dec 1, 2019)

Mine'sa66 said:


> If you pump the pedal up, can you still overpower it to the floor or do you have to wait before it will fade?


i have to wait for it to fade


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## Mine'sa66 (Oct 30, 2019)

Tim68 said:


> i have to wait for it to fade


So you pump the pedal up and it's firm and hard and stays there. You wait a few minutes and then you have to start all over? The pedal is on the floor and you can pump it up?
Hmmmmm....
You get full fluid flow out of all the bleeders from every pump or do you not get fluid until the pedal pumps up?


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## Tim68 (Dec 1, 2019)

Mine'sa66 said:


> If you pump the pedal up, can you still overpower it to the floor or do you have to wait before it will fade?
> 
> 
> LATECH said:
> ...


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## Tim68 (Dec 1, 2019)

Mine'sa66 said:


> So you pump the pedal up and it's firm and hard and stays there. You wait a few minutes and then you have to start all over? The pedal is on the floor and you can pump it up?
> Hmmmmm....
> You get full fluid flow out of all the bleeders from every pump or do you not get fluid until the pedal pumps up?


I don’t know the answer 
I‘ll bleed them again and let you know


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## PontiacJim (Dec 29, 2012)

It is very important to have all parts match. This is why I asked if a "kit". When parts are gathered from several sources, sometimes they are not matching.

ASSUME you are testing the brakes/pedal effort with the engine running and good engine vacuum. If no vacuum in the booster, the pedal will go down low to the floor and could give a false test of the brakes.

As LATECH pointed out, there are differences in the MC. Drum/drum, Disc/Drum, and Disc/Disc. Then there are differences in the MC bore size - very important in both moving brake fluid, pedal travel, and pedal effort. If you, for example, mismatched an MC with a small piston bore, you won't be able to move enough brake fluid to apply the disc brake caliper pistons, but if you are "close with enough fluid, your pedal stroke may go right to the floor and will be very easy. If you have a bigger bore MC, it moves a greater volume of fluid during the pedal stroke - think a cylinder in a gas lawn mower engine vs a Pontiac engine, the smaller bore of the lawn mower engine would no way move as much air per stroke as a single stroke of the bigger Pontiac engine. You might have to fill that tiny lawn mower cylinder up 10 times to squeeze out the same amount of air a single stroke of the Pontiac engine can move. Now if we had a brake fluid reservoir fitted large enough to the Pontiac cylinder bore/stroke and that same size fitted to the lawn mower cylinder - you push the pedal on the Pontiac cylinder 1 stroke and the brakes would apply. If we push the redal on the lawn mower cylinder, the brakes would not apply because we have not moved enough fluid to apply the brakes. You might have to pump the pedal 7 times just to get enough fluid into the brake system and by that time, you might have no fluid left in the reservoir.

So very simple example, but calipers have larger bore pistons than wheel cylinders - so you need enough fluid going from the MC when the pedal is pushed, AND, you need enough volume of brake fluid being moved in a single stroke of the MC.

I am not brake expert, but I believe many who do a 4-wheel disc change will use a Corvette MC as the Corvette has 4-wheel discs.

You also want to make sure the brake booster rod is adjusted correctly so that it pushes on the MC to apply the MC. If our of adjustment, ie too short, you will be pushing in on the pedal and won't have any action until the rod takes up the gap distance and then pushes in on the MC - so you won't have the correct pedal travel and may not get the full travel of the MC piston in moving fluid to apply the brakes.






Speedway Tech Talk - Booster Adjustment


Tim talks about brake booster adjustment.




www.speedwaymotors.com





You might want to go over this post if you have not already done so.









FAQ - Braking: POWER BOOSTER ANGLE and DISC vs DRUM


I have seen a couple posts with regards to the angle of the master cylinder. Hmmm. Why are some parallel with the engine, some positioned as an angle up, and some aftermarket set-ups too high and hit the hood? Hopefully, this may help a couple of you and answer a few questions. The use of...




www.gtoforum.com





AND, not sure how you are bleeding your brakes. Use a helper. Don't use one of those vacuum brake bleeder pumps - they don't work well and will pull air around the bleeder valve versus pull fluid from the line. You can also "gravity" bleed the brakes by cracking them open and let the fluid run out. I do this to each wheel, one at a time doing the farthest one first, then when I am ready, I get a helper for that last little bit to check for air. Don't let the brake fluid get to low or the MC can become empty and you have to start all over again.


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## BearGFR (Aug 25, 2008)

LATECH said:


> Hard to tell if the "distribution block" is anything more than a safety valve. It must be a safety valve as it has the switch for the Brake warning light.


That's all it is, at least on my '69 anyway. Inside there's a piston that can move "forward" and "backward". If there's a pressure imbalance, the pressure difference will force the piston in one direction or the other so that it completes the circuit that turns on the warning light.

Reading your description, my first thought was Master Cylinder. Unfortunately, these days just because a part is "new" doesn't guarantee that it's good.

If your brakes were working ok and you didn't have a soft/no pedal condition before you changed out parts, then (Spock mode on) logic would tend to suggest that the changed parts should be suspected first, provided you didn't make any grievous mistakes in installing them (like getting the caliper bleeds on the bottom instead of on the top, or not getting the MC adequately bench bled)

If you've bled the system and have gotten all the air out, there aren't any leaks where fluid is getting out, and you don't have incorrectly matched components like PJ mentioned, then that pressure has to be leaking >somewhere< either past caliper piston seal(s) or MC seals.

NAPA tends to be better than most, but still one never knows if something you get off the shelf is truly new and tested, or is something that got returned by a previous customer and was returned to stock erroneously.

Bear


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## ponchonlefty (8 mo ago)

i think you still have air in the system. if it turns out you definitely got all the air out. the master is by passing. get someone to help you bleed the system. that way you can see pure fluid and not air. i have changed from 1 1/8 bore to 1 inch bore it changes the peddle feel but would not go to the floor. hope this is helpful. but you know, cars are faster without brakes. im joking.


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## RMTZ67 (Mar 12, 2011)

Question...is someone pumping the brakes and holding while you bleed the brakes? If so is it squirting out or drizzling?


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## armyadarkness (Dec 7, 2020)

I had a 70 vette, and C3's were NOTORIOUS for being difficult to bleed. I thought I was pretty slick, but the car had me outmatched. I finally bought a Motiv bleeder and now I can do a whole car, by myself, in 5 minutes, and far better than any manual bleed.

You may want to invest in one. It has many other uses and serves very well in routine maint tasks.


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## Mark Dougherty (Sep 6, 2018)

Hey, just a thought since I am reading what sounds like air in lines and assuming bleeding is done right. I replaced entire brake system original on my 67 Tempest (lines, booster, cylinders, prop valve) and could not get firm pedal. Old time mechanic said check for air in brake line over the rear differential where brake line splits at a high spot to the left and rear wheel. If you bleed out that fitting with a helper to pump and hold brakes you just might find air trapped like I did - which fixed me up. Good luck.


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## pkentander (Dec 9, 2021)

Tim68 said:


> I have just completed the disc brake conversion for all four wheels. I have also replaced all the brake lines and master cylinder. I bench bled the master cylinder and bled the lines. Had a couple leaks that have been resolved. Not getting any air when bleeding but still petal goes to the floor. It will pump up but slowly goes to the floor.
> seems like there is still air in the lines but after bleeding them numerous times and not seeing any more air.
> Will the proportioning valve cause this issue? That’s the only thing I have not replaced.
> I have bled braked numerous times before but have not had this hard or time to get the petal pressure.
> any help?


I replaced everything just like you did. I used stainless steel lines. I don't know if you did or not but it takes a lot more force to seal them than regular brake lines. I ended up back bleeding my lines to get everything to work properly. You might google that and give it a try. I does sound like you said air in the lines.


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## RMTZ67 (Mar 12, 2011)

I would get a helper to pump and hold the brakes. Keep doing ea brake in the proper sequence until it is squirting like a young man. No old man dribble....Crack it open . Get plenty of fluid out. Making sure the mc does not run dry. Clear 1/4 hose to see all the action. After that, a system like Army described is perfect. Just want to pump the sh!+ out of it to make sure no air no blockage.


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## Machinest-guy (Jul 19, 2019)

You might try testing the system pressure. Front to rear and side to side. Buy two gauges because the measurements need to be done simultaneously. You can isolate which line or portion of the system has an issue very quickly. 









Amazon.com: Strange Engineering P2360 Brake Pressure Test Gauge : Automotive


Buy Strange Engineering P2360 Brake Pressure Test Gauge: Gauge Sets - Amazon.com ✓ FREE DELIVERY possible on eligible purchases



www.amazon.com





I was doing a lot of disc brake conversions and creating modified brake systems a few years ago. These tools were a great help. Good luck. stay safe. Ladd


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## Tim68 (Dec 1, 2019)

I bled them again after it sat for a week or so and got them workin.
Thanks for everyones input


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## PontiacJim (Dec 29, 2012)

Tim68 said:


> I bled them again after it sat for a week or so and got them workin.
> Thanks for everyones input


Sitting for a week should not have made a difference. If you are using DOT 5 brake fluid, from what I read, it can be difficult to remove all the air from the lines/fluid - which would make sense letting your car sit for a week to let any air work its way out.

I think I would be very careful driving the car, ensure your emergency brake is fully functional, and after a little seat time, bleed the brakes again.


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## Mine'sa66 (Oct 30, 2019)

Tim68 said:


> I bled them again after it sat for a week or so and got them workin.
> Thanks for everyones input


Many difficult brake/coolant bleeds have been solved by hoisting the front or rear of the car 4 feet and going home for the night.
Some trapped air found it's way to a better spot.
Glad you got it.


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## Machinest-guy (Jul 19, 2019)

Good morning. I have ruined a few brake systems with dot 5 and various silicon brake fluids sold to the automotive aftermarket. 

While these fluids don't absorb water as Dot 4 fluid will, this is a curse not a blessing for the majority of car owners. Water vapor in the atmosphere becomes inducted into the brake system through the vented filler cap. No way around that because the system needs to be vented to work (and a sign of a clogged vent is difficult bleeding). Vent caps should be removed or loose when bleeding brakes. 

With Dot 4 fluid atmospheric moisture is absorbed into solution and eventually needs to be flushed out - normal service - at intervals well known through service publications. Dot 5 fluid forces water to accumulate as drops at low points in the system which then rust from the inside out. Unseen, and unknown to anyone that hidden damage can cause sudden failure. If left to run it's course over several years time the mung and muck, which is a byproduct of rust corrosion and consequent reactions to the silicon fluid breaking down, you'll see some very awful fluid clogging your master cylinder or coming out of the bleeder screws. By then it is too late. The entire brake system will need service / replacement.

Dot 4 fluid will do the same thing but it takes several years, maybe decades, longer to happen because water drops won't form until the fluid is fully saturated - then it will promote water drop formation the same as Dot 5 or silicon fluid does. What we are talking about is saturation time. A few years for Dot 4 fluids and from the first day with Dot 5.

My understanding is silicon fluid was popular for use in museum vehicles where it had less likelihood of damaging paint and those cars didn't absorb very much moisture because they were never used. Then in the 70's it was popular in some race applications because of a higher boiling point than Dot 3 fluid. I'm not sure who uses it now. Dot 4 fluid, and other special fluids for specific model applications are the correct fluids to use now. Dot 3 fluid is functionally obsolete. Nothing using Dot 3 will be hurt with Dot 4. 

I'd guess there is still some air in your system. 

When brake systems which contain air are bled by pumping the pedal that air can be foamed into the fluid requiring some time to separate - hours or overnight. Then it can be removed by gentle pressure bleeding or gravity bleeding. You can test how long to wait by pouring some brake fluid into a clear container, then capping and shaking it to foam it. Then watch how long it takes to settle out. Different brands of fluids will settle at different rates. When the brake fluid you test is clear again you can assume the fluid in the system has de-foamed also. You cannot successfully bleed a foamy fluid.

Pressure bleeding should be done at under 5 lbs pressure. I've found two lbs is a good number to follow. Gravity bleeding, in my opinion, is the best way to bleed brakes because brake tubing is sized to form a meniscus that will, by capillary action, draw fluid along the tube without mixing air into it. I'd recall about 75% of a couple of thousand cars I've rebuilt brake systems on were successfully gravity bled. 15% needed to be pressure bled. Virtually none were pedal pumped because there is too much risk of over stroking an old master cylinder into an internal rust pit or mung pile wrecking it. But gravity bleeding takes time because you bleed until the fluid changes color in the catch pan, plus 5 minutes or so to be sure a steady flow is emerging from the bleeder - not just an interrupted drip fooling you. Raising the car end for end can help remove trapped air - mostly caught in an incompletely or incorrectly bench bled master cylinder. Master cylinders should be bench bled "nose low" to move the air inside them towards the compensation port and aid in elimination. In service master cylinders are generally run "nose high" so reversing this for bench bleeding repairs can be very helpful. 

Very few cars - maybe 4 or 5 come to mind, required vacuum bleeding like done on some aircraft. Vacuum applied to the bleed port sucks the brake fluid down from the cockpit reservoir and through a landing gear assembly down into a caliper. It works on cars too, but seems to be a lot of messing around when I've tried it. One-way check valves to bleed brakes can help because air can be drawn back into a system past the bleeder screw threads when pedal pressure is released that the valve will stop. But again its my opinion they promote making a mess and fooling around while hoping they do some good.

Good luck. Ladd


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## Khmike (Jun 21, 2021)

On a related note and in an effort to avoid the mix-n-match parts issues, has anyone here installed a complete 4-wheel disc conversion from drum? 

Thx


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