Bleeding Replacement Master Cylinder

[Nehmo]

1996 Chevrolet Lumina APV 3.4L

The Master Cylinder and Anti-lock braking systems (ABS) are together. I've removed them and replaced the Master Cylinder part. The Master Cylinder came with 2 plastic tubes and green plastic fittings that fit into the outlets of the ABS.
Instructions say to bench bleed the master cylinder before installing in the minivan. I don't have a vice, so I plan to do this on the vehicle. My problem is that I'm not sure how to do it. The ABS has 4 outlets that go to each wheel. I assume I attach the tubes to the outlets and put the other end in the reservoir. But which of the 4 do I attach the 2 tubes?

[Schurkey]

1. You'd need four tubes.
2. You're going to pump the ABS full of air.
3. If you do this on-the-vehicle, the master cylinder is probably going to be tipped "up" in front, making it really, really hard to get the last of the air out of the master cylinder. Ideally, the master is mounted on a fixture or in a vice with the front of the master tipped "down" a little during bench-bleeding.

Bench-bleeding the master on-the-vehicle, with the ABS connected, is a really bad idea.

4. I bet you will need a scan tool to chatter the valves in the ABS in order to properly bleed the ABS on-the-vehicle, AFTER the master cylinder has been properly bench-bled.

[Nehmo]

Originally Posted by Schurkey

1. You'd need four tubes.
2. You're going to pump the ABS full of air.
3. If you do this on-the-vehicle, the master cylinder is probably going to be tipped "up" in front, making it really, really hard to get the last of the air out of the master cylinder. Ideally, the master is mounted on a fixture or in a vice with the front of the master tipped "down" a little during bench-bleeding.

Bench-bleeding the master on-the-vehicle, with the ABS connected, is a really bad idea.

4. I bet you will need a scan tool to chatter the valves in the ABS in order to properly bleed the ABS on-the-vehicle, AFTER the master cylinder has been properly bench-bled.

I now can go to a place where I can use a vice tomorrow, Saturday 19th. But I don't have 4 tubes. (Only 2 came with the master cylinder.) I can get the plastic tubes somewhere, but the green threaded inserts may be a problem. I don't have a car to run around to places. https://qrcd.org/3aio

[Nehmo]

Originally Posted by Nehmo

I now can go to a place where I can use a vice tomorrow, Saturday 19th. But I don't have 4 tubes. (Only 2 came with the master cylinder.) I can get the plastic tubes somewhere, but the green threaded inserts may be a problem. I don't have a car to run around to places. https://qrcd.org/3aio

I used a vice and bench-bled the master cylinder/ABS unit. Then I installed in in the minivan.
This sounds like a simple procedure, but it was rather difficult. The position of the master cylinder/ABS unit in this vehicle is far back under the low-slope windshield. It's hard to access. Also, the outside temperature yesterday was around 100° F, and I couldn't move the vehicle out of the sunlight.
I still have to do a normal full-system bleed. If I had the $, I'd buy one of those one-person bleeding machines https://qrcd.org/3atu or a hand vacuum pump. ChrisFix describes how to make a simple one-person bleeder https://youtu.be/1wwq1Vlk4Wg.
You try to avoid spending $ wherever you can, but I've found buying a tool that makes a job easier is seldom regretted. You may not use it again, but later you may give it to somebody who needs it. They will be greatly appreciative.

[Schurkey]

Originally Posted by Nehmo

I used a vice and bench-bled the master cylinder/ABS unit.

You didn't split the master from the ABS unit? I bet the ABS has heaps of air trapped inside.

Originally Posted by Nehmo

I still have to do a normal full-system bleed. If I had the $, I'd buy one of those one-person bleeding machines https://qrcd.org/3atu

A pressure-bleeder that doesn't separate the brake fluid from the air the pressurizes it with a rubber diaphragm, is SPECIFICALLY NOT RECOMMENDED by GM.

The brake fluid will absorb humidity out of the pressurizing air. The fluid is already contaminated as soon as it's installed.

Originally Posted by Nehmo

or a hand vacuum pump.

I gave-up vacuum bleeding decades ago, ESPECIALLY on drum brakes. You have to seal the bleeder-screw threads or you pull air into the wheel cylinder or caliper, and particularly with drum brakes, you can pull air past the seals on the piston. In that case, you'll never know when to stop bleeding because there will always be air bubbles.


You are almost certainly going to need a proper scan tool to bleed the ABS unit.

[maxwedge]

Agreed on the scan tool to bleed the abs, I was just going to post that.

[Nehmo]

Originally Posted by Schurkey

You didn't split the master from the ABS unit? I bet the ABS has heaps of air trapped inside.

Now that you made me think about it, I should have bled the master cylinder before I reattached it to the ABS unit. That's probably the reason the master cylinder only came with 2 plastic hoses.
It would have been easier to bleed the master cylinder by itself. It's hard to get a grip with the vice on the combined mc/ABS because the ABS is in the way.
It's already on the van now. I'm going to try to bleed via the wheel zerk fittings.

Originally Posted by Schurkey

A pressure-bleeder that doesn't separate the brake fluid from the air the pressurizes it with a rubber diaphragm, is SPECIFICALLY NOT RECOMMENDED by GM.

The brake fluid will absorb humidity out of the pressurizing air. The fluid is already contaminated as soon as it's installed.


I gave-up vacuum bleeding decades ago, ESPECIALLY on drum brakes. You have to seal the bleeder-screw threads or you pull air into the wheel cylinder or caliper, and particularly with drum brakes, you can pull air past the seals on the piston. In that case, you'll never know when to stop bleeding because there will always be air bubbles.


You are almost certainly going to need a proper scan tool to bleed the ABS unit.

Can I do that later? If the van bleeds OK, will the brakes function without the ABS unit being properly bled? I don't have access to a scan tool now and can't buy one either.
I'm planning to bleed at the 2 zerk fittings on the front of the ABS before I bleed at the wheels. I already bled at those points when I had the unit in a vice, but doing it again couldn't hurt.

(Added Edit) Wow! Although it's only 95° F out there, I couldn't last more than 15 minutes. I had to close up and go back in. I pity all the people in the world who endure this temp (and worse) without air conditioning. When you begin to get old, as I am doing at 69, you wonder if any physical shortcoming is because of age. Maybe I could take the heat if I were 10 years younger.

[maxwedge]

I've had some success pulling the abs fuse, that sends the internal valves "home", which can help bleed the abs unit, but you should have bench bled the master.

[Nehmo]

Originally Posted by maxwedge

I've had some success pulling the abs fuse, that sends the internal valves "home", which can help bleed the abs unit, but you should have bench bled the master.

I'll try that. I had planned to bleed while the vehicle was off. But I can start it and pull the ABS fuse. It can't hurt. It's the bottom center fuse on the Instrument Panel Fuse Block on the left side of the inside of the glove box. I'll try this when I go out to do my next bleeding. https://youtu.be/7h74TZvcxic

I've already partially bled the minivan. I started with the master cylinder and then went to the right rear. I used a plastic tube immersed in a bottle to make a one-person bleeder. I couldn't seem to get anything out of the lines going to the rear brakes. I'm not sure what that means. I doubt the lines are clogged. I'm going out to the van now to figure it out.
Nonetheless, the condition of the brakes is much improved now that a new master cylinder is in there. I actually have some braking power now (although the pedal pushes down somewhat mushy. Before I had nothing. I suspect I now only have the front disk brakes.

[Nehmo]

I bled both the front brakes, and it was somewhat of a problem because the bleeder valve (AKA zerk fitting) on the caliper cylinder took a different size wrench than the ones on the back. The back used a 5/16" wench. On the front, I used a 3/8" socket, but that was difficult to get on. Maybe it's a metric size. I don't know. In any case, I managed to bleed the front wheel cylinders. The pedal seems like it will stop the vehicle.
For now, I just need to make the minivan drivable. I'm in Kansas City, Kansas, and the previous owner is in Kansas City, Missouri. The metro is unusual in that a state line divides it. In order to retitle and register, I need to first provide insurance, bill of sale, and a Missouri title to the Kansas Motor Vehicle Department and get a one-day tag. Then I need to drive the minivan to a Sheriff to have them give a declaration saying the VIN on the title matches the one on the vehicle. Then I take the declaration to Motor Vehicles and have them do the normal title transfer and registration.

But there are some other problems with the van, and the break bleeding exposed one of them. When I removed the front-left tire & rim, one of the studs broke. The remaining 2 are not enough to allow driving. I need to replace the stud or the whole hub. (I'll start another thread for this.)

[Schurkey]

Originally Posted by Nehmo

I bled both the front brakes, and it was somewhat of a problem because the bleeder valve (AKA zerk fitting)

Bleeder valves look sorta-kinda like grease zerks. They serve completely different purposes, they are not interchangeable.

Originally Posted by Nehmo

The back used a 5/16" wench. On the front, I used a 3/8" socket, but that was difficult to get on. Maybe it's a metric size. I don't know.

Front is 10 mm. Rear is 8 mm.

Originally Posted by Nehmo

When I removed the front-left tire & rim, one of the studs broke. The remaining 2 are not enough to allow driving. I need to replace the stud or the whole hub. (I'll start another thread for this.)

Might as well stay on this thread. IF (big IF) you can find the proper studs, that'll be way easier than replacing the hub. Good luck finding the proper studs.

[Nehmo]

Originally Posted by Schurkey

Bleeder valves look sorta-kinda like grease zerks. They serve completely different purposes, they are not interchangeable.


Front is 10 mm. Rear is 8 mm.


Might as well stay on this thread. IF (big IF) you can find the proper studs, that'll be way easier than replacing the hub. Good luck finding the proper studs.

I should have realized the bleeder valves were metric. I thought the minivan was partially SAE because of its age. Is everything on it metric?

Why do you think the wheel studs will be hard to find? I seemed to have found them with a quick search. Dorman Wheel Stud 610-254.1 https://qrcd.org/3bpv

One other question: Since I need to remove the brake disk & caliper in order to access the hub well enough to replace the studs, what size is the hex wrench on the slider bolts of the caliper? I haven't figured out how to look up bolt sizes unless I get lucky in a search.

[Schurkey]

Originally Posted by Nehmo

I should have realized the bleeder valves were metric. I thought the minivan was partially SAE because of its age. Is everything on it metric?

MOSTLY metric.

Originally Posted by Nehmo

Why do you think the wheel studs will be hard to find? I seemed to have found them with a quick search. Dorman Wheel Stud 610-254.1 https://qrcd.org/3bpv

Any time I go looking for wheel studs, it's for a trailer, or something ancient. I end up going into a store with a good one in my hand, and trying to match something up.

Originally Posted by Nehmo

One other question: Since I need to remove the brake disk & caliper in order to access the hub well enough to replace the studs, what size is the hex wrench on the slider bolts of the caliper? I haven't figured out how to look up bolt sizes unless I get lucky in a search.

I've never worked on a Lumina APV. My Lumina car uses Torx T60 for the bolts/spacers on the caliper, and the spacers are always seized to the bolts making them difficult to remove. Generally takes a propane torch + effort to free-up the spacers again. I don't remember what socket size the caliper bracket bolts take. 17mm--maybe.

[Nehmo]

Originally Posted by Schurkey

Any time I go looking for wheel studs, it's for a trailer, or something ancient. I end up going into a store with a good one in my hand, and trying to match something up.

Part # 610-254 from Advanced Auto is not a correct match. The diameter of the splined section is too small, and the splines are coarse, not fine.
Unless somebody knows the real aftermarket part number, it's a matter of searching and going to the parts stores. Normally, it wouldn't be much of a problem, but without a vehicle, every trip has to be arranged somehow.
I'm considering using 610-254, which fits snugly but turns with a bit of torque. I could make a welder with the battery and jumper cables and weld a spot on the back of the hub securing the stud. I need a welding electrode, though.
The GM part number is 9595178. But I just bought ones with that part number, and they don't match either. I'd suspect the hub (with studs) I have is an aftermarket one that was exchanged for the original, but it doesn't look like anything but the original.

[Nehmo]

I had trouble finding wheel studs that would fit. Even the ones from the Chevrolet dealership, GM# 9595178, had a knurl diameter that was too small. Eventually, one of the Advanced Auto stores allowed me to climb a ladder with my vernier calipers and search through their boxes. The ones I found didn't match in the coarseness of the knurl, but so what? But they used the same lug nut and worked.
Once I got the wheel with all the studs together, I returned to the brakes. I was previously working the brakes when the missing studs forced me to change my focus. Previously, after a partial bleed, the front was working, but the back wheels didn't even get fluid to them when I tried to bleed. Now, after leaving the brake project for a couple of days, I discovered the fluid was gone. I then found a leak that had eluded me before. The picture attached has the left side of the van on top. I need to replace the brake line.
The metal lines are going to require a few bends. I sent away for a 3/16" kit https://qrcd.org/3db0