Bench bleeding master cylinder

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jhumphrey

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I couldn't find this answer in a search, so I'll make a new post for those searching in the future:

What's the proper procedure for bench bleeding a 97 4Runner brake master cylinder with the cardone brake tool (http://my.cardone.com/techdocs/10908BBF bench bleeder flyer.pdf)? The instructions have two different methods - one you open both ports as you inject the fluid, the other method you leave one port plugged as you inject.

Does anyone know which method our MCs use?
 
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Strange about the website.

Anyway, it's a tool that looks like a big syringe. You fill it with brake fluid and inject it into an open port of the MC. Once the bubbles are not longer present, you do the same thing with the secondary port.

Apparently there are 2 types of MC. One type requires you to leave the 2nd port closed while injecting and the other requires both ports to be open.

Does anyone know what type of MC is in a 4Runner?
 
One of the ways to bleed the MC is to use the plastic adapters that came with it, as well as the hoses, and just pump until there's no air that comes out anymore.
 
I accidentally let my master cylinder go empty gravity bleeding the new to me 97 of all the nasty brake fluid.

I did a Hail Mary and hooked up my motive pro pressure bleeder and bread all the brakes at 10psi. Brakes feel great. No bench bleeding required.

If I had to bench bleed it I would have just spun short brake lines into the MC fittings and bent them to go into the master cylinder resivour and pumped until no air bubbles.
 
Doc2012 said:
One of the ways to bleed the MC is to use the plastic adapters that came with it, as well as the hoses, and just pump until there's no air that comes out anymore.
Click to expand...

Yes, the MC came with two needles and tubes and outlines this procedure: use a vice, fill the MC with some fluid, and manually activate the piston until there are no more bubbles. It says that it can take 70+ "pumps" to get the air out.

The cardone bleeder is supposed to allow you to get the bubbles out in 3-4 "injections". It ultimately comes down to whether or not I am to unplug one or both ports. I'm not sure if it matters or not. The 4runner's MC looks different than most MCs anyway (two reservoirs with two different caps that can be removed); the 4runner has one cap only (cant really see the secondary reservoir).

The "typical" MC bleeding procedure:

The following process is supplied with each CARDONE replacement master cylinder. You can help our customers by stressing the importance of following every process we include with our parts, to prevent warranties and increase sales.

Transfer proportioning valves, switches or other components to the replacement master cylinder (as applicable).

Tighten bleeder plugs into ports (bleeder plugs may be in parts kit or master cylinder reservoir).

Support the master cylinder in a vise in a level position. Never clamp onto the body of the master cylinder.

NOTE: Units with remote reservoirs should be bled on the vehicle. It is VERY IMPORTANT that the body of the master cylinder be kept level during the bleeding process.

Fill reservoirs halfway or until reservoir ports are covered. Always use new brake fluid from a sealed container as specified by the vehicle manufacturer.

Install reservoir lid so brake fluid does not spray from reservoir during bleeding process.

Using a blunt tool or dowel (brake pedal if mounted in vehicle), SLOWLY press in and release the master cylinder piston using short strokes of 3/4” to 1”. NEVER STROKE PISTON MORE THAN 1”. Repeat this step until resistance to piston movement is firm and less than 1/8”.

IMPORTANT NOTE: On step-bore master cylinders, WAIT 20 SECONDS BETWEEN STROKES. This will allow air trapped in the quick take-up valve to rise into reservoir. MASTER CYLINDER BODY MUST BE LEVEL.

Install master cylinder on vehicle. DO NOT remove bleeder plugs until brake lines are ready to be installed. This prevents air from entering the unit and brake fluid leaking out.

Remove one bleeder plug at a time from the master cylinder and connect the proper brake line to that port. Repeat this step for remaining brake line ports. Be sure fluid level is maintained during installation of brake lines and that all fittings are clean before installation. Bleed brake system according to vehicle manufacturer’s procedures and specifications.

Verify proper pedal action before moving vehicle. Do not road test vehicle until correct pedal feel and travel are obtained.

NOTE: If firm brake pedal action results using bleeder plugs, but becomes soft after installation in vehicle, the problem is not the replacement master cylinder.

Using the "syringe":

CONVENTIONAL MASTER CYLINDERS
1. Mount master cylinder in a vise by the mounting lugs as level as possible.
2. Remove plug from one brake port (if installed).
3.Attach supplied rubber grommet to the tip of the bleeding syringe.
4.Fill reservoir with new fluid from a sealed can of the type specified for the
vehicle until reservoir is at least half full.
5.Hold empty syringe tightly against uncovered brake port.
6.Slowly pull syringe plunger until syringe is approximately half full. See
picture 2.
7. Purge air completely from syringe but leave the syringe at least half full of
fluid. Hold syringe tightly against uncovered port and inject fluid back into
the master cylinder. See picture 3.
8. Repeat steps 5 through 7 until no air bubbles are observed rising in
reservoir.
9.Replace port cap.
10.Repeat steps 2 through 7 for all other brake line ports.
Refer to supplied installations and vehicle service manual to complete
master cylinder installation

OR

STEP BORE MASTER CYLINDER
1. Mount master cylinder in a vise by the mounting lugs as level as possible.
2. Remove plugs from both brake ports (if installed). Place a pan below
brake line ports to catch fluid during bleeding.
3. Attach supplied rubber grommet to the syringe tip.
4. Partially fill reservoir until inlet ports are completely covered using brake
fluid from a sealed can of the type correct for the vehicle. Fill syringe
with new fluid, being sure to purge all air from syringe.
5. Place rag under primary brake port. Hold syringe tightly against reservoir
inlet and slowly inject fluid. Repeat until fluid flows from brake port and
all air is purged. See picture 2.
6. Fill syringe with new brake fluid. Be sure to purge all air from syringe.
7. Hold syringe firmly against the primary brake line port and slowly inject
fluid into port. Observe fluid rising within reservoir from primary inlet,
checking for air bubbles. See picture 3.
8. Repeat injecting new fluid until no air bubbles are observed.
9. Cap port.
10. Repeat steps 6 thru 9 for secondary port.
Refer to supplied installations and vehicle service manual to complete master
cylinder installation


So, is the 4runner a "conventional" or "step bore" MC? My guess is step bore, but I want to make sure.

Or would it be easier/more prudent to do this method (found on Yotatech):

From the 2001 Tacoma Factory Service Manual;

BLEED MASTER CYLINDER
HINT:
If the master cylinder was disassembled or if the reservoir becomes empty, bleed the air from the master cylinder.
(a) Disconnect the brake lines from the master cylinder. SST 09023–00100
(b) Slowly depress the brake pedal and hold it.
(c) Block off the outlet plug with your finger, and release the brake pedal.
(d) Repeat (b) and (c) 3 or 4 times.

So my thoughts are that it may be "easier" to hook up the MC (I'm going to be swapping out the brake booster at the same time), fill it up, put the hoses on (looped back into the MC), and have an assistant slowly pump the brakes until the air is gone. Basically, what seems to be the best (and easiest) method to go with?
 
Last edited:
Im getting ready to do this over the weekend. Any advice would be great...I don't think I can use the tool to bleed because it wont fit in the reservoir of the MC. Since I wont have access to a vice, can I use the below procedure to bleed it (installed on vehicle):

BLEED MASTER CYLINDER
HINT:
If the master cylinder was disassembled or if the reservoir becomes empty, bleed the air from the master cylinder.
(a) Disconnect the brake lines from the master cylinder. SST 09023–00100
(b) Slowly depress the brake pedal and hold it.
(c) Block off the outlet plug with your finger, and release the brake pedal.
(d) Repeat (b) and (c) 3 or 4 times.
 
jhumphrey said:
Im getting ready to do this over the weekend. Any advice would be great...I don't think I can use the tool to bleed because it wont fit in the reservoir of the MC. Since I wont have access to a vice, can I use the below procedure to bleed it (installed on vehicle):

BLEED MASTER CYLINDER
HINT:
If the master cylinder was disassembled or if the reservoir becomes empty, bleed the air from the master cylinder.
(a) Disconnect the brake lines from the master cylinder. SST 09023–00100
(b) Slowly depress the brake pedal and hold it.
(c) Block off the outlet plug with your finger, and release the brake pedal.
(d) Repeat (b) and (c) 3 or 4 times.
Click to expand...

I don't know about a new one, but that worked like a charm for me after I effed up the first time I pressure bled my brakes and ran the reservoir dry.
 
A whole thread to turn a procedure that's pretty simple into an complex procedure?

Remember that the web is full of info outside this forum as well.
 
TheDurk said:
I don't know about a new one, but that worked like a charm for me after I effed up the first time I pressure bled my brakes and ran the reservoir dry.
Click to expand...

Thanks for the help! This is the first time I've ever had to mess with a MC, so I'm learning as I go. I found that procedure over at Yotatech (in their 95.5-04 Tacoma/96-02 4runner section). I wasn't sure if depressing the brake all the way down would hurt anything (since during a traditional bleed you aren't supposed to stroke further than 1").

As to csp saying I'm over complicating the procedure, this is my first MC swap and want to make sure I do it correctly and not eff anything up, so I'm asking a ton of questions. I guess he decided that ridicule was the better way to go rather than contributing to the conversation/being helpful to someone who has never done it before.
 
jhumphrey said:
Thanks for the help! This is the first time I've ever had to mess with a MC, so I'm learning as I go. I found that procedure over at Yotatech (in their 95.5-04 Tacoma/96-02 4runner section). I wasn't sure if depressing the brake all the way down would hurt anything (since during a traditional bleed you aren't supposed to stroke further than 1").

As to csp saying I'm over complicating the procedure, this is my first MC swap and want to make sure I do it correctly and not eff anything up, so I'm asking a ton of questions. I guess he decided that ridicule was the better way to go rather than contributing to the conversation/being helpful to someone who has never done it before.
Click to expand...

Oh, just so you feel better, that's a direct quote from my '99 FSM, so it should work on your '97. As I recall, the reason for that rule is so you don't push old crap out of the MC by going beyond normal travel. Should not be an issue on a new MC with new fluid. But I'm just making that up, don't call it gospel. Brakes are not my specialty. Hence the screw-up on the bleed.
 
Last edited:
TheDurk said:
Oh, just so you feel better, that's a direct quote from my '99 FSM, so it should work on your '97. As I recall, the reason for that rule is so you don't push old crap out of the MC by going beyond normal travel. Should not be an issue on a new MC with new fluid. But I'm just making that up, don't call it gospel. Brakes are not my specialty. Hence the screw-up on the bleed.
Click to expand...

Thanks Durk. My plan is to do this this weekend. I'm going to hook the MC up to the brake booster and install everything at once. Then start the bleed procedure with a helper. I'll post up the results as soon as I get it done. Once again, thanks for all your help!
 
I completely forgot to update this (in case someone is searching and finds this thread):

I replaced both the MC and brake booster. It must've been one of them, because I had decent brakes after the swap.
 
jhumphrey said:
I completely forgot to update this (in case someone is searching and finds this thread):

I replaced both the MC and brake booster. It must've been one of them, because I had decent brakes after the swap.
Click to expand...

Which master cylinder bleed procedure did you use? You mentioned that you were going to try the FSM one mounted on the car. Did you have to make sure the master cylinder rail was level? I'd have to jack the rear end high in the sky before my master cylinder rail is level since it sits so raked mounted against the booster.

I only ask before I did a bench bleed with the two tubes into the reservoir on a new OEM master cylinder, Then I bled the entire system on the car using power bleeder once I reinstalled the master cylinder. I'm getting really bad brake booster delay unless I pre prime the pedal prior to engaging the brakes fully. I have to press pretty hard to lock up or engage ABS in rain which is sad. Literally all the foot strength I've got. My next stop is to try and replace the old nasty gasket between the master cylinder and the booster as the booster function tests seems to pass.
 
I just wanted to add my 2 cents for people having trouble with brake pedal basically going to the floor.

So my rear axle seals are leaking (which is another matter) and leaked past the seal on the passenger side, which let oil get on my rear brake pads. I decided to replace them when I did the seal.

One of the things I noticed before I replaced was that I was having to press the pedal farther to the floor to get enough braking. That is when I found I had leaking rear seals, as I was looking for the cause of the brake pedal.

I did a brake bleed after having the axle out and rear pad replaced. I had a pretty firm pedal feel, but it would slightly sink. I gave it a test drive down the hill I live on and I was so concerned about not having any braking ability I went right back into the garage.

I decided at that point to replace the master cylinder. I bought the new one from O'reily think it's called Brakes Best or something like that. I bench bleed it but the lines were too short and the plastic plugs for bench bleeding were leaking. As a result, I think it may have had a little air in it. Also, it might be that I had air in the system, perhaps I let some air in it while putting on the 231's. Anyway, new master is on and I wont be replacing it unless I have to.

After installation, I bleed the system again, pedal felt fine (2 person method), and this time when I tested it I didn't even pull out of the driveway it felt so bad.

Distressed that there was something more serious wrong and/or I wouldn't be able to bleed it myself, I took a break and looked for some more answers. I found a thread that said to bleed it twice, then bleed it twice more with it truck on, then trigger ABS, then bleed, then bleed again with truck on. So 6 bleeds! Uhhh

Anyway, I decided to bleed it again with truck on. I had my dad push the brakes a couple of times while on the rear and got no bubbles. Then I had him start it up. Immediately I got a good bit of bubbles. Swiched to other rear, more bubbles. Then Fronts, got nothing.

Test drove it, much improved, but no firm braking like you would want under panic conditions. Truck would hardly nose dive. I found a bit of dirt just off the side of the road that I could use to trigger ABS braking. Triggered it about 5-6 times.

Went back had dinner and about 30 min break. Then bleed it again, tested without engine, no bubbles. Tested with engine, got another bit of bubbles. Switched side, not much, then front, again nothing.

Test drive, much better again. Firm pedal, no longer goes down. Front end dips pretty good.

I still can't lock up brakes or trigger ABS on the street. Not sure about that one. Might be the cheap pads I am using on the fronts, might check those and replace them with something else (Just super cheap rockauto pads). Also may still have a bit of air in it, I will probably try to bleed them again in a few weeks during Christmas vacation again.

Anyway, that's my story. If it helps anyone out then was worth writing! Good luck!
 
If I remove the old master cylinder and replace it with a new one, then bleed, will I be able to remove all the air (even though it may take a while and a lot of fluid)? I don't have a vice or a work bench to bench bleed it
 
stever1000 said:
If I remove the old master cylinder and replace it with a new one, then bleed, will I be able to remove all the air (even though it may take a while and a lot of fluid)? I don't have a vice or a work bench to bench bleed it
Click to expand...
no, you need to bleed the MC first.

"bench bleed" is just a name. it can be done on the vehicle. just don't hook the lines up.
buy a short length of the proper brake line, then cut it in half. use that line on the MC ports, with the other ends routed back into the reservoir. then pump slowly, until there is no more bubbles. once all the air is out, then you can hook the vehicles line up.
 
nevada said:
no, you need to bleed the MC first.

"bench bleed" is just a name. it can be done on the vehicle. just don't hook the lines up.
buy a short length of the proper brake line, then cut it in half. use that line on the MC ports, with the other ends routed back into the reservoir. then pump slowly, until there is no more bubbles. once all the air is out, then you can hook the vehicles line up.
Click to expand...

Great, that sounds easier than buying a work bench and a vice :yo:
I'm relieved to hear I can "bench bleed" with it mounted in the 4runner

Thank you!
 
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