Brake system questions (also bleeding nightmare)

[maurice]

Hey guys, I’m cutrently bleeding my vw and I ran into some questions about if I have a correct setup.

Before I ask my questions, here’s my setup:
Front - 4 piston wilwood discs from airkewld
Rear - 4 piston cnc discs
Master is from the airkewld kit, assuming it’s a super
Hand brake is inline hydraulic 3/4” from cnc
Biasing valve is wilwood and sits on the end (inlet) of the hand brake

I was previously running the front and master with my old brake setup, using 2 piston cnc brakes in the rear. The hand brake, rear brakes, and biasing valve are new.

I’m having trouble bleeding, the fronts bled great. The rears seemed to be doing well, but I get air bubbles when I use the hand brake to bleed - it does push a lot more volume. Is that something I should have bench bled? Could it or my biasing valve be trapping air?

Also, I didn’t think about it before, but will my master support 4 piston calipers in the rear? CNC has shut their doors and I am unable to ask them.

I’ll post pics later tonight

[Ol'fogasaurus]

I'm having problems posting to this so if things duplicate I will remove one.

Bleeding the rear brakes with turning brakes in the system usually requires a second person. One to pump the cylinder and one to bleed. Gravity bleeding usually doesn't work on the as the turning brake slave cylinder is filled in the top of the cylinder(s) which usually puts things out of the gravity bleeding process. Power bleeding should work by converting the system below... if needed.

I would start by bleeding both rear brakes first starting with the right side which is a tad farther away from the MC than the left side. If things bleed OK showing that the brakes slave cylinder is filling then you need to start using the turning brake handles to ensure that there is no bubbles in line/system.

Start working on the turning brake by re-bleeding the right side by actuating the brake pedal. When it is hard or on the floor then actuate the turning brake handle for that side and having the bleeder valve open then when it stops being soft or hits bottom you close the valve, let your foot off the pedal but keeping the turning brake handle fully applied then, using the foot pedal, pump the brakes which will/should eventually put the turning brake handle back to it's stop. If the brake is still soft repeat. If it is still soft then look for air leaks in the system (fluid will not always show at the leak area).

When the one side is done then start on the other side. Again, make sure the MC is kept full during bleeding.

This should work if not let me know.

Lee

[maurice]

Thanks for the help! I read somewhere that bench bleeding it might be the only option. But I like your approach and I’m for sure going to try this and get back to you.

[maurice]

I may have hooked up my lines backwards on the inline hand brake. Is the in suppose to be coming in from the side, and the out from the very back? Or vice versa? I’ll try to get a pic on in a minute

[maurice]

image.jpg

[Ol'fogasaurus]

image[1] copy.jpg

I'm a now a little confused on this one. Is this a "line lock" or a setup to just lock the differential so it doesn't just drive one wheel at a time when off-roading setup; e.g., to stop one wheel drive on an open differential to help on not the best surface(s) for traction. Or is it a single handle push-pull turning brake setup which I now don't think it is?

When I said you do one side at a time this would have been for turning brakes but it might still might work for other setups. What looks like a pressure adjuster at the front is what is confusing me the most.

It looks like the side connection to the cylinder is for raw pressure in from the MC and the one on what looks to be an adjustable pressure valve would head to the brakes via the "Tee" in the rear that send pressure to both brakes. Bring that it is sitting at an angle: is this for Drag racing?

Need some additional information on this.

Lee

[maurice]

It’s a line lock setup, a pass thru staging brake. I live in San Francisco and need a hand brake for the hills, also for drag racing.

I was pretty sure I hooked up the lines correctly - side line to back wheels, front line from the master feeding into the hand brake. I checked a video of someone doing one online and he had the same routing.

I did your technique, and I think I got a little more air out.
I loosened my calipers and pointed the nipples straight up, I got a small amount of bubbles out of them. Eventually got to a point where I am seeing no bubbles at all. My pedal has started to firm up, but definitely not where I want it.


As far as the car goes, it’s a mid engined Subaru powered turbo nitrous 66 bug. Hence the reason I have such big brakes.

[maurice]

C989E952-9314-44C0-8832-97909B4E11A8.jpeg

Here are the directions. Pretty close to yours

[Ol'fogasaurus]

I'm happy to hear that it worked... at least worked somewhat. I'd still check the connections for full seal. As I said you can still get air in the system but still not have fluid coming out.

turning brakes on the blue buggy.jpg

I had a similar problem with my turning brakes years ago and all I did was disconnect, pull the line out then re-install (some bending required to ensure of a better entrance angle [I wasn't sure it was off but just in case]) and that was the end of it. Being mine was a turning brake one side (the driver's side) would lock and I would have to open the bleeder to relieve the pressure. It only locked periodically which was part of the confusion.

This is a very old pix of the setup before the 3rd complete rebuild of the buggy. You can see that the bend down from the lines for each rear brake into the turning brake cylinder is now a bit away from the entrance (e.g., a straight line entry).

(a re-statement) The entry angle of the brake line can be a big problem. If the bend at the end of the brake line being too close to the connection can have a skewed entrance angle not allowing you to tightening things straight to the cylinder seat.

When I was building a car for drag racing I used an electric line lock. I put the button on the shifter handle just below the grip, I would engage the brake pedal to lock the rear brakes then push the button to hold the lock. Rev the engine to launch RPMs (preload) then, when I got the bottom yellow light finger off the button and "whoopie"!

Lee

[maurice]

Figured it out kinda. I’m pretty positive there is no air left in the system, my hand brake feels real solid.

I bled it with the proportioning valve completely open as instructed. But I never tested the brake with the valve in any other position. I closed it up to the most restrictive setting and bam, a good pedal. Slowly loosening it brings a shittier and shittier pedal... not sure what my options are at this point.

Maybe I do have too much brake for my master, and allowing them full flow drops my pedal down more than acceptable.

Or maybe it has something to do with the valve itself - I have too much rear brake to not have one.

Thoughts?

[Ol'fogasaurus]

Figured it out kinda. I’m pretty positive there is no air left in the system, my hand brake feels real solid.

I bled it with the proportioning valve completely open as instructed. But I never tested the brake with the valve in any other position. I closed it up to the most restrictive setting and bam, a good pedal. Slowly loosening it brings a shittier and shittier pedal... not sure what my options are at this point.

Maybe I do have too much brake for my master, and allowing them full flow drops my pedal down more than acceptable.

Or maybe it has something to do with the valve itself - I have too much rear brake to not have one.

Thoughts?

Single cylinder MC or dual cylinder MC? If it is dual cylinder MC are the front brakes connected to the larger of the 2 cylinders?

By any chance are the rear brakes oversized and the MC was not fitted correctly to it.

When the adjustment is made so it works well ("most restrictive setting") do the rear brakes also work well?

If things are OK on the road with the restrictive setting then maybe there you are.

Lee

[maurice]

Dual master cylinder.

I don’t know if the master is fitted appropriately with the rear brakes, that was one of my questions and worries.

I unfortunately can’t test how well the rears work under most restrictive just yet. I’m having trouble with my ecu, I may have fried it, and can’t get the car to start. I somehow have a buddy with the same rare ecu (japan only from the 90’s), and we’ll get it tested in the next couple weeks. I’m also missing a few vital parts to get it street worthy to test.

I’ll get back to you on how the progress goes with this brake situation. I really appreciate your advice

Maurice

[Ol'fogasaurus]

Dual master cylinder.
Maurice

In a dual master cylinder the front brakes usually attach to the rear cylinder and that is because the bigger bore piston for the cylinder is in the rear. With a bigger piston in front the piston assy would not go through the smaller bore cylinder if that cylinder was in the rear.

Not 100% sure this is true all the time as there can be some differences I am not aware of. Been many a year since I did a complete dual piston brake job front to rear.

Lee

[Bruce2]

In a dual master cylinder the front brakes usually attach to the rear cylinder and that is because the bigger bore piston for the cylinder is in the rear.

The bore of a VW master cylinder is the same all the way through. The front brakes are attached to the front end of the MC because there are two ports for the two sides. The long line to the rear connects to the lone rear port of the MC.

[Ol'fogasaurus]

In a dual master cylinder the front brakes usually attach to the rear cylinder and that is because the bigger bore piston for the cylinder is in the rear.

The bore of a VW master cylinder is the same all the way through. The front brakes are attached to the front end of the MC because there are two ports for the two sides. The long line to the rear connects to the lone rear port of the MC.

Some of the cylinders I worked with years ago were the way I said. As I tried to say: I am not sure what they are doing now days.