Order of bleeding brakes

[Shootey]

I have a 1941 Buick in need of a brakes bleed. My question is in what order are the wheel cylinders bled. I’ve always heard that you start with the farthest from the master cylinder and work closer and closer. But in reading a 1952 Buick shop manual it instructs the reverse, that is you start with the closest. A 1949 Delco brake service manual instructs the same as the shop manual. 
Another  question is do you close the bleed screw prior to the release stroke of the pedal.  I have also heard and read that you leave the screw open for the entirety of the bleeding of the particular wheel cylinder. 
 

Thanks. 

 

[NailheadBob]

L/F , R/F , L/R , R/R in that sequence

 

open the bleeder - push brake pedal down to floor board close bleeder and release brake pedal

 

keep checking and adding brake fluid as needed

 

Bob

[Joao46]

Maybe this is like an oil discussion, but I follow the furthest to closest to master cylinder rule and prefer to have the helper press the brake first then I open and close bleeder screw

[31Buick96S]

4 hours ago, Shootey said:

I have a 1941 Buick in need of a brakes bleed. My question is in what order are the wheel cylinders bled. I’ve always heard that you start with the farthest from the master cylinder and work closer and closer. But in reading a 1952 Buick shop manual it instructs the reverse, that is you start with the closest. A 1949 Delco brake service manual instructs the same as the shop manual. 
Another  question is do you close the bleed screw prior to the release stroke of the pedal.  I have also heard and read that you leave the screw open for the entirety of the bleeding of the particular wheel cylinder. 
 

Thanks. 

 

Newer vehicles with dual master cylinders and diagonal braking use the farthest to nearest method. There are exceptions and you should always follow manufacturer recommendations.

[avgwarhawk]

For me RR, LR, RF, LF. 

[joe_padavano]

This is one of those questions like which way does the toilet paper hang. I've got Oldsmobile factory manuals from 1961 through 1985, and even these are not consistent. I'm still waiting for someone to tell me what the effect is that they are trying to prevent by specifying the order. And even then, when one has a dual circuit system (split front/back), why does it even matter at all?

[Andy J]

I always did it as avgwarhawk states.However,the shop manual for my '51 Pontiac says LF,RF,LR,RR;backwards of what I always have done it. I bled them starting farthest to closest,it worked just fine,and I didn't lose any sleep over it.

[Frank DuVal]

I found it doesn't matter. Either farthest or closest. As speaking of farthest, one would have to look at the rear axle the see where the T is mounted (same for IRS) to tell if RR or LR was farthest. So who cares... either works.  😉

 

if if I have a person to press the brake pedal (which is very rare) I just use my finger over the bleeder as a check valve.  Without a helper I use the Mighty Vac or One Man Brake Bleeder, you know, the one shown in most shop manuals.  Need a “pop” bottle and hose that fits the bleeder. 

 

People talk about power bleeders but I haven’t used one in over 50 years of wrenching. 😀

[Joao46]

The only issue I’ve found with mighty vacs is you can get false bubbles as air enters through the loose bleeder screw threads. 
The best way short of a 2 man job is a pressure bleed with pressure added to the reservoir. But that has its own hazards of a blowout if you’re not careful with the pressure or connections and now your car has a nice brake fluid spritz all over it.😠 

[joe_padavano]

1 hour ago, Frank DuVal said:

People talk about power bleeders but I haven’t used one in over 50 years of wrenching. 😀

I have a Vacula pneumatic vacuum bleeder and it is probably the best tool purchase I've ever made. One pass at each wheel cylinder and I'm done. I don't even need to bench bleed the M/C, this will pull the air out. Even the ABS system on my truck didn't phase it. A real Vacula is pretty spendy if purchased new. Fortunately I got mine at a swap meet decades ago for peanuts because no one (not even the seller) knew what it was. There are clones on the market now for under $50.

 

[Lee H]

1 hour ago, Joao46 said:

The only issue I’ve found with mighty vacs is you can get false bubbles as air enters through the loose bleeder screw threads. 
The best way short of a 2 man job is a pressure bleed with pressure added to the reservoir. But that has its own hazards of a blowout if you’re not careful with the pressure or connections and now your car has a nice brake fluid spritz all over it.😠 

Agree. I used vacuum or a helper for a long time, until I recently converted my ‘62 to a dual system, and for the life of me I couldn’t get all the air out. That’s when I got a power bleeder, and that solved the issue immediately.

[Bloo]

I start at the furthest away bleeder (look where the hose drops to the axle in the back, the furthest may not be what you would suspect). That's how I was taught to do it in tech school long ago. As far as I know it was never a requirement, just suggested that you might get the system completely bled faster that way. I have seen factory shop manual procedures for some cars that say the opposite. If I know that is the case for a particular car, I'll follow the shop manual. Maybe my way is an old wives tale, I don't know, but the only thing that was ever alleged was that it was quicker. It works OK for me on the kind of cars we generally talk about in this forum. Of course there are oddballs and outliers that might need something strange like one end of the car jacked up, but that's pretty rare.

 

I vacuum bleed. The el-cheapo kits with a mityvac get the job done just fine. They are a pain to use, and the real answer is the Vacula in @joe_padavano's post. That is much lower stress because the air compressor does the work, and the bottle isn't constantly tipping over, etc. Either way you just have to get your head around the fact that the bubbles will never stop because the bleeder threads leak air. It's fine. Just pull until you have clean fluid, and move on to the next bleeder in your sequence.

 

After verifying I have a pedal, I prefer to do one or 2 squirts at each bleeder the old fashioned 2-man way at the end, starting over in the sequence, with a squirt at the master cylinder at the last if it is practical to do it. This is just to be sure I have all the air out. It beats jacking the car up a second time. It isn't strictly necessary.

 

When using the old 2-man procedure for the whole bleed, and there is no pedal, what you DON'T want to do is push and hold the pedal clear to the floor. Only push and hold about as far as the pedal would have gone when the brakes were working. Yes it takes longer, and more bleeding. The reason for this warning is if you take the pedal further down than it normally goes, you are dragging the rubber cups over rust, and you may discover that a master cylinder that was working an hour ago has mysteriously failed.... Oops. Of course if the master cylinder is a new or rebuilt one that you just put on you can ignore this. Vacuum bleeding or pressure bleeding mostly sidesteps this issue by getting the pedal up early.

 

I don't like pressure bleeders for hobby work. I loved them in shops. The reason is you usually have to load them with the brake fluid. Glycol brake fluid, which most of us use, should be treated like milk. It's perishable. It should be used from fresh sealed containers, and any leftovers kept with the cap sealed tightly when stored. It definitely should not be kept around for years after being opened. Two months is the limit at my house. In my opinion, 6 months is pushing it. This is a non-problem in a shop that is constantly doing brake jobs. In a hobby situation, vacuum bleeding makes it way easier to manage the fluid.

 

Edited February 1 by Bloo (see edit history)

[CarNucopia]

I tried a different way of bleeding my brakes last year which made the process very easy. I'm curious if I'm doing something dumb that I haven't figured out yet.

 

Like many, I don't have anyone to help do a two person bleed. For my motorcycle, I bought a product called Speed Bleeders which has a check valve in the bleeder hardware. With this, you press the brake to bleed and the valve closes before the fluid can be sucked back in the line.

 

 

I was hoping to do this on my Caterham, but couldn't find one that was the right thread. As an alternative, I put another Speed Bleeder in-line,  between two clear tubes, after caliper.

 

 

I used a zip tie and hose clamp to be certain nothing disconnected under pressure. I took a video as I pumped and see the fluid goes in only one direction when I repeatedly pump the brakes.

 

 

[joe_padavano]

1 hour ago, Bloo said:

The el-cheapo kits with a mityvac get the job done just fine.

I have not had success with the Mityvac units. Air will always leak past the threads of the bleeder screw when it's loose. With a constant vacuum source like the Vacula, this is irrelevant since the air always goes into the bleeder, not back into the system (physics is your friend). I've found that with the Mityvac, when you release the handle to pump it, air can get back into the system.

[PFitz]

4 hours ago, Joao46 said:

The only issue I’ve found with mighty vacs is you can get false bubbles as air enters through the loose bleeder screw threads. 
The best way short of a 2 man job is a pressure bleed with pressure added to the reservoir. But that has its own hazards of a blowout if you’re not careful with the pressure or connections and now your car has a nice brake fluid spritz all over it.😠 

Same here. I work by myself now. Have adapters for pressurizing master cylinder reservoir using shop ait through a regulator adjusted to low pressure. But mostly, I have one of the old spring-loaded telescoping brake pedal pushrods that I got from an old truck mechanic. Adjust it to length slightly longer than seat to pedal. Then push the ends together to shorten and tension the spring. Then one end rests against the front of the seat and the other end presses the brake pedal. I set it then go open a bleeder. When the brake fluid starts to slow down through the clear vynal drain tube I close the bleeder screw. Then I go let the pedal up to refill the master cylinder bore and reset the pushrod. 

Edited February 1 by PFitz (see edit history)

[dodge28]

There are many different ways to bleed bakes, some efficient and some not so efficient. The goal is to achieve a nice high pedal. Pedal height is specified by the manufacturer .The most difficult brakes to bleed is when the master cylinder is below the level of the wheel cylinders. This is the case of my 1928 Dodge Senior. I WORK ALONE. I use a transparent plastic tube with a check valve from Amazon for 5 dollars.  The end must be inserted in a in a container with fluid.  It  helped a little but I still need a helper to pump the pedal and bleed the old fashion way. Common sense will tell you that the bleeder nearest the master cylinder is where to start and the furthest cylinder last.

[Bloo]

1 hour ago, joe_padavano said:

I have not had success with the Mityvac units. Air will always leak past the threads of the bleeder screw when it's loose. With a constant vacuum source like the Vacula, this is irrelevant since the air always goes into the bleeder, not back into the system (physics is your friend). I've found that with the Mityvac, when you release the handle to pump it, air can get back into the system.

I just pump it way up and let it bleed. I haven't really had any trouble with that because it stays lower than atmospheric for a while. "Bottle won't stay put" is the main problem. I never use my good hand pump for this. There is a good chance the pump is going to get full of brake fluid and need washing out. They're annoying as hell but get the job done for me, and work in places where there is no compressed air. Nothing beats a Vacula though.

[joe_padavano]

18 minutes ago, dodge28 said:

Common sense will tell you that the bleeder nearest the master cylinder is where to start and the furthest cylinder last.

That isn't clear. Starting furthest away theoretically will pull more air from the system the first time, but as I and others have said, I've never found a substantive difference one way or another.

[Gearheadengineer]

2 hours ago, CarNucopia said:

I bought a product called Speed Bleeders which has a check valve in the bleeder hardware.

Speed bleeders rock! I still make sure to put a hose over the end so the fluid goes into a container, but they make one person bleeding easy. I used one on a hydraulic clutch setup that I was struggling with and finally got all the air out. The thread sealant keeps air from getting in that way. I like your solution for your caterham. Brilliant!

 

I’ve never tried the Vacula. Looks like a good option. I’ve used my MightyVac. It works but I’ve had the same issues noted by others. Speed bleeders are easier. 
 

 

 

 

[Shootey]

Thank you all for your help. I have my son to man the pedal so we will do it the old fashioned way. I know many of you have been through this before on the forum and I appreciate your doing it again. In the end it should be pretty simple and we will get it done. 

[dodge28]

The wheel cylinder position on the backing plate , how many cylinders on one backing plate . 3 o clock and 9 o clock position on the same backing plate ? 12 o clock position on self adjusting brakes all needs to be done differently. I have been there.   

[kramaton]

I like the hose attached to the bleeder screw then in a bottle of brake fluid method. You can do it yourself and the fluid does not get everywhere.

[Lee H]

From Motor’s, 1949. Always start with the most distant wheel first.

[joe_padavano]

2 hours ago, Lee H said:

From Motor’s, 1949. Always start with the most distant wheel first.

Unfortunately it still doesn't say why. I stopped responding to "because I said so" when I moved out of my parent's house.

 

By the way, the following is from Oldsmobile factory-issued Chassis Service Manuals. The excerpt on the left is from 1970, the right from 1985. No, neither one of these is a diagonal-split braking system. And note especially the part about "bleed the master cylinder last" in the 1970 manual.

 

 

 

 

Edited February 2 by joe_padavano (see edit history)

[Shootey]

The Motors manual talks about the order of bleeding but it also talks about repeatedly pumping the pedal without closing the bleeder between each pump. That was my second question—is it necessary to do so, to close the bleeder before letting the pedal return to the release position?  And if not why all the discussion of check valves?  Maybe I’m missing the subtleties of later, more sophisticated braking systems. 

[dodge28]

Shooty, that is a valid question. As I said before I get a helper to pump the pedal slowly, when the pedal come up hold the pedal down and I crack the bleeder once and close it quickly, Repeat until no more bubble comes out. Then go to the next wheel. The key here is to pump slowly. allowing the master cylinder to fill. Finally  I hold the pedal down hard  and keep it down for a for minutes to check for leaks. 

I am not condeming any one .Each to his own.

 

[Frank DuVal]

11 hours ago, Joao46 said:

The only issue I’ve found with mighty vacs is you can get false bubbles as air enters through the loose bleeder screw threads. 

I fixed that issue early on. Just a wrap and a half of PTFE tape on the threads (or two if some of the newer loose fitting bleeders).😉 No worries about shards of tape getting in the brake system. The seal is at the end of the screw, not the threads!

[Frank DuVal]

1 hour ago, Shootey said:

—is it necessary to do so, to close the bleeder before letting the pedal return to the release position?

Yes, otherwise you are just sucking air back into the system! You are bleeding to get all the air out of the system.

 

The check valve is just a modern version of the hose and "pop" bottle one man bleeder that was in lots of shop manuals. Kramaton mentioned it too.

[dodge28]

Frank Du Val, bingo

[Stude17]

The only reason that I can see to follow either sequence ie from furtherest to closest or closest to furtherest is that you follow the sequence chosen thereby making sure all wheel cylinders are bled.   Just my thoughts.  I have always used the furtherest to closest.

[Lee H]

Joe P, I find it interesting that Motor’s, by 1969, had backed up a bit on their earlier statement to start farthest first:

 

What this tells me: “It doesn’t matter, but we all have engineers with strong opinions”

 

Frank and Shootey: they also backed up on the open bleeder question:

 

My personal opinion on this - if you are working with a drum brake system, there is a very good chance that the master cylinder has a built-in residual pressure valve(s) that were designed to to maintain a low ≈ 5-10 psi on the wheel cylinders to keep the rubber cups primed and ready, so there is a minimum of hydraulic “slop” when you hit the pedal. Brake fluid, in theory, shouldn’t return to the MC unless the system is closed, and the brake shoe return springs force it back past the RPV.
 

 

Edited February 2 by Lee H (see edit history)

[Buick35]

I'm glad I have mechanical brakes on my 35.

[joe_padavano]

3 hours ago, Lee H said:

Joe P, I find it interesting that Motor’s, by 1969, had backed up a bit on their earlier statement to start farthest first:

 

What this tells me: “It doesn’t matter, but we all have engineers with strong opinions”

Considering that Chevy cars of that period used exactly the same brake system as did other GM cars, the different bleeding orders are illogical.

[Shootey]

I guess I stirred up a hornet’s nest. Thanks everyone for all the input. Since I apparently have a choice on order I’ll follow the Buick 1950s Shop Manuals and start at left front. And I’ll close the bleeder before releasing the pedal. 

[Joao46]

The only issue I’ve found with mighty vacs is you can get false bubbles as air enters through the loose bleeder screw threads. 
The best way short of a 2 man job is a pressure bleed with pressure added to the reservoir. But that has its own hazards of a blowout if you’re not careful with the pressure or connections and now your car has a nice brake fluid spritz all over it.😠 

[Joao46]

Maybe For was right. Mechanical is the way to go

[joe_padavano]

21 minutes ago, Joao46 said:

The only issue I’ve found with mighty vacs is you can get false bubbles as air enters through the loose bleeder screw threads.

So long as there is continuous vacuum on the system (as provided by a Vacula or similar vacuum bleeder) then this is a non-issue. The air cannot physically get into the brake system, only into the bleeder. The problem I've had with the Mityvac is the risk of air getting back into the system when you pump it.

[hook]

You must remember. If you have three engineers in the room, you will have at least five or more opinions. And they will be absolute on at least four of them.

[Frank DuVal]

On 2/2/2024 at 3:29 PM, joe_padavano said:

The problem I've had with the Mityvac is the risk of air getting back into the system when you pump it.

Not sure how this could happen. You mean if the hose slipped off? ❓  Just pump it up again with the hose on. Same if the hose slips off using the Vacula.

[joe_padavano]

8 hours ago, Frank DuVal said:

Not sure how this could happen. You mean if the hose slipped off? ❓  Just pump it up again with the hose on. Same if the hose slips off using the Vacula.

The air leakage around the bleeder screw threads. With the Vacula and constant vacuum that isn't a concern because all the air goes into the bleeder, not back into the system.