Hey guys,

I've got an issue with my brakes and at this point in my build I've lost the will to troubleshoot.
I put a 97 camaro 10bolt lsd w/discs rear end in and wanted to freshen up the 30 odd year brake system with my LS1 swap.

I've replaced the master cylinder with a new thirdgen one, put a wilwood adjustable proportioning valve in, made new 3/16" brakes lines for the 2 front brakes and a new 3/16" line for the rear brakes.
I got all the flaring tools, and adaptors needed etc, and also bought a vacuum bleeder to bleed the system.

After multiple attempts using the vacuum bleeder as well as the old style of getting a friend to pump the brakes while I crack the valve, I still have the pedal going to the floor.

I cannot see any leaks anywhere in the system and with the car off and the brake pedal loaded with my body weight (180lb) there's still no leak anywhere, but no brakes.

It was my first time benchbleeding a master cylinder so maybe I got that wrong, but at this point I'd rather buy my way out of it than start taking everything apart again only to be in the same situation.

What I was wanting to know is, is there a master cylinder that I can get that is already 3/16" inverted / SAE flare fittings that is compatible with the stock brake booster?
I've seen a lot of threads on here but usually people are looking for a master cylinder with the same fittings as the thirdgens to not have to remake lines, but seeing as I've already swapped out the lines for the 3/16" stuff, it makes more sense to ditch all the adaptors and chances for leaks and just go direct.

Anyone have any ideas?

 

Fill up the master cylinder and then crack open the rear brake lines and let it just sit like that until fluid start dripping out. Then do your pedal bleed. Sometimes it's harder than heck to get fluid through a dry prop valve but gravity will get the fluid through if you're patient.

 

That's the thing, I've got fluid coming out, and the rears don't seem to have any air bubbles, but the front just keep showing air bubbles.
I can't really tell if its air coming from the lines or just the shitty rubber piece going over the bleed valve, or the coarse thread of the bleed valves letting air in after it.

I've got a spare fluid cap, and was thinking of modifying that to put a few psi of compressor into the reservoir to try and help push it through.
The new lines I made for the front were a bit different and ended up routing against the firewall instead of along the k-member so I was thinking maybe they have air trapped in there that isn't coming out with the bleed.

Also, should the fluid be trying to pump up through the reservoir when i put the pedal down?
I feel like it shouldn't but if I was to push the pedal down quickly I'll get a little fountain spurt of brake fluid shoot out from the bottom of the reservoir..

Is there any way to bleed the master cylinder in the car if I jack up there rear enough to level it?
I was thinking if I did that the new lines are soft enough that I could unbolt the MC from the booster and replace the shaft with a slightly longer one to allow full motion to bleed it. Would that work?

 

I use a Mityvac hand pump. But I think I'd rather move to a motive pressure bleeder.

 

Technique is a big deal. I never could get my brakes bled until I learned a decent technique. Starting with a dry system is more difficult than flushing a system that's already filled.

Don't stab or pump the pedal. Large air bubbles can be purged. Tiny air bubbles can't. Pumping the pedal or moving it too fast will churn large bubbles into tiny bubbles. Once that happens you're screwed and you have to let the car sit for about 20 minutes or more for the bubbles to coalesce into larger bubbles again. Sink the brake pedal at a slow/moderate speed and don't go all the way to the floor. Put pressure on the pedal first, then open the bleed valve, and close the valve while the pedal is still in motion. In other words, always be in movement when the valve is open. Easy, smooth and steady movements. Let up at the same slow/moderate rate. Pause at the top. Pausing helps keep tiny air bubbles forming. NEVER let the fluid level get low or you'll suck air into the master cylinder and you'll be screwed.

After the pedal starts to firm up for both front and rear brakes, gently press on the pedal and barely crack the fittings at the master cylinder. You might be surprised how much air comes out. Tighten up again without ever lifting the pedal. This is quick and won't take much. Bleed the brakes again. I'm totally serious. Your brake pedal should feel fantastic after this.

This is what has worked for me. Other people will have variants of this but we all have one thing in common --- we're slow and smooth on the pedal and only open and close the valve under pressure.

 

Thanks for that.
I think just to be sure I'll start again from scratch and pull the master cylinder out, bench bleed it, then re-bleed everything from there.
For master cylinder I've read 2 ways of doing it: Make some lines to screw in that loop back into the reservoir, or cap the ports so you can confirm when it has built pressure and doesn't move the piston; Which is the better one?

 

Bleeding the master cylinder just means looping a tube back into the reservoir and flushing fluid through until no more air comes out. Usually the tubes are clear (and come with the master cylinder) so you can see bubbles. Don't stroke the plunger all the way when bench bleeding, it apparently can damage the seal. Short strokes, maybe half stroke. It kind of difficult, lots of spring force behind that plunger.

It's going to start leaking the moment you try to put it in the car until you hook up the lines again. No worries, just don't let the fluid level drop too low.

 

Oh, forgot to mention the fountain from the master cylinder is normal. It's part of the quick take-up circuit in the stock master cylinder. Lay the cover over the reservoir so fluid won't splash into your engine bay.

In general, keep air away from brake fluid when you aren't filling. Keep the cap on the bottle between fills. Brake fluid absorbs water from the air and you don't want that in your system. Minimize time exposed to air. Throw away whatever is left in the bottle when you're done, it's not worth keeping. (that's why I buy a bunch of the small bottles)

 

Stupid question, but I've done it once: are you sure the calipers aren't upside down?

 

Haha, no I think they're the right way up. 85 firebird the bleed nipple is on top facing the front of the car... That's correct yes?

 

Update, solved the problem.
So the main issue I think was air in the master cylinder still. I pulled it off dripped brake fluid everywhere, re-bench bled it with the rubber lines attached to the steel lines and completely submerged in the reservoir.
As the air came out the steel lines I stopped, worked the air to the top, then pushed it the piston further in to drop the air out, then let the fluid suck back in after slowly releasing the MC piston.

After that I then reinstalled it, again leaking fluid everywhere but got it back on and tightened up again.

Lastly after that was done I set the adjustable proportioning valve all the way to open. Bled the back, then the fronts and then after that reset the proportioning back where I think it should be.
I now have brakes, and when running, but looks like I now have a bit of a low vacuum issue. The cam is a VCM710 232/234 so not sure if that's the cause or the tune is still not quite right yet, but the booster holds vacuum fine.

I'll connect up my vac gauge to see what it's producing at idle, but I'm thinking of getting one of the UP28 electric vacuum pumps to fix this, or a 2L vacuum cannister but not sure how good the UP28 pumps are.

 

I don’t run a vacuum ball, I have a 5.7L with a 231-239 on a 110lsa and have good brakes.

around 900 I have 55-60kpa. Or about 16-17” according to the map sensor.