Trying to figure out brake problem with rear disc upgrade

[Apogee]

Originally Posted by CreepinDeth

Man, I really don't know. LOL

I bled EACH caliper at least 5 times with a vacula, then my hand with a 2nd person (old fashioned way), and then with the 1 man bleeder bottle with help again. I don't see anymore bubbles coming out. So I just ASSUMED there was no air because hell it should have came out by now I thought. If I couldn't get it out that many times, I figured it will never come out so it's GOTTA be clear.

I'm going to bench bleed the master though because while I had it hooked up to the booster , I left it unplugged while I was flaring some new fittings. It's possible air got back in the MC. Thanks for replying to my email too bro. I will try that, then if it's fine, I'll just install the new Raybestos premium 79 new MC I just ordered. My Camaro used the same MC and went like a BREEZE the 1st time around. This one is being a real bitch to me.



BTW what did you mean by "A single master cylinder" ??
The 79 Vette MC has 2 equal size chambers and is 1 1/8".....so you lost me. I'm still kinda new to this so excuse my ignorance.

Wow...I should buy some stock in whatever brand brake fluid you're using.

By single master cylinder, I meant a single tandem master cylinder, one with one bore size and two pistons and outlets so that you have some safety should one circuit fail. The alternative being dual master cylinders like those used in a race pedal setup with a balance beam between the two. These setups allow you to run different bore MC's front and rear, giving you the flexibility to run huge caliper mismatch's should you want to and still getting the bias you want/need.

As for the MC fittings, I'll usually bleed the MC fittings first by cracking them one at a time while under pressure just so I don't have to push those air bubbles all the way through the system, especially if it's already been filled. It also helps if you run your hard lines to the MC slightly uphill so that they hold more fluid prior to installation. The air that I've had difficulty bleeding from the MC at times seems to be tiny bubbles trapped in or around the seals. No amount of moving fluid through the MC seems to remove them without some tapping with a dead-blow hammer to help dislodge them.

Tobin
KORE3

[CreepinDeth]

Originally Posted by Apogee

Wow...I should buy some stock in whatever brand brake fluid you're using.

I've killed a gallon already......wasn't fun.


Okay, so I guess the '79 Vette MC is a single. I hope this new MC works out better.

Originally Posted by Apogee

As for the MC fittings, I'll usually bleed the MC fittings first by cracking them one at a time while under pressure just so I don't have to push those air bubbles all the way through the system, especially if it's already been filled.

So let me make sure I understand this.
You crack the 2 fittings while pressing the plunger in on the MC.....to get the air out.
Then before releasing the plunger you tighten the 2 plugs ???

....or did I misunderstand that ??

[Apogee]

Originally Posted by CreepinDeth

...So let me make sure I understand this.
You crack the 2 fittings while pressing the plunger in on the MC.....to get the air out.
Then before releasing the plunger you tighten the 2 plugs ???

....or did I misunderstand that ??

That's about right, except I just do one fitting at a time since I'm usually juggling a rag and trying not to get brake fluid everywhere. Have someone press and hold the pedal while you crack open and then close one fitting at a time and repeat until you're satisfied. I've found that 1-2 times per fitting seems to be plenty most installations.

Tobin
KORE3

[GregWeld]

I bench bleed the M/C on the bench rather than on the car. It's hard to get all the air out of the M/C sometimes. I use a large phillips screwdriver as the push tool... and that way I can really bottom the plunger. I have a set of lines I use that hook up to the outlets and return to the M/C reservoir and I can SEE that there is not a single bubble left before the install. I cap it -- and leave the lines on - get it bolted up - toweled up - and swap the lines over.

One other thing that is a mistake I've found several times trying to help someone with "brake issues".... Not every M/C is the same line configuration - i.e., some M/C's run the front reservoir to the fronts and some run the front reservoir to the rear. The way I've found to check for this is while I'm bench bleeding it - I plunge slowly while looking for the fluid flow FIRST in which bowl of the reservoir - that reservoir should be to the fronts. If you do this a couple of times - you'll see what I'm talking about - you'll see fluid just a nano second before in one bowl or the other. That wouldn't give you a mushy pedal - I'm just adding this since you're using parts you may or may not be familiar with...

If you bench bled the M/C - and went thru a gallon of fluid - I say you've got a bad M/C and should probably just get a new one.

[CamaroAJ]

just going to throw this out there since i know first hand this can happen. do you have the rotors bolted on or the wheels bolted on? it may sound like it shouldn't matter but this just happened to me the other day and then i remembered i didn't have the rotors bolted onto the hub. but i blead the system then had a soft pedal. bolted the wheels back on and have nice hard pedal. the rotor being able to move side to side even though its just a little bit is enough to push the pistons back and give you problems

[GregWeld]

Just one last thought on this problem... I think we'd all ASSume that you know how to bleed brakes.... which is the furthest away first -- so passenger rear first - then driver rear - then passenger front - then driver front....

[PRRC]

I would say that 1 problem with this set up your running is the 1/4 line to rear calipers. It's just to large of a diameter for a disc. set up.

[CreepinDeth]

Well , my new Raybestos premium NEW 79 Vette master arrived today.
So tomorrow I bleed it Tobin's method on the vise. Front angled down.....and this one came with plugs.
The 2 reman's came with tubes for the OTHER MC bleeding method. So that's a good start.

Originally Posted by CamaroAJ

just going to throw this out there since i know first hand this can happen. do you have the rotors bolted on or the wheels bolted on?

I did it both with the rear + front wheels off while bleeding AND did it with the wheels on.

Originally Posted by GregWeld

Just one last thought on this problem... I think we'd all ASSume that you know how to bleed brakes.... which is the furthest away first -- so passenger rear first - then driver rear - then passenger front - then driver front....

Yes sir. I did my research first. I followed that procedure EACH and EVERY time.

Originally Posted by GregWeld

I bench bleed the M/C on the bench rather than on the car. It's hard to get all the air out of the M/C sometimes. I use a large phillips screwdriver as the push tool... and that way I can really bottom the plunger. I have a set of lines I use that hook up to the outlets and return to the M/C reservoir and I can SEE that there is not a single bubble left before the install. I cap it -- and leave the lines on - get it bolted up - toweled up - and swap the lines over.

EXACTLY word for word how I did both my Vette masters.
Except I didn't plug them going from the vise to the install.
1st one went good on the 78 z28, front C5 brakes, rear stock drums, 1st time worked.
2nd one not so good on my 442, front stock disc, rear Baer disc, total TARFU mush pedal.....lol

One other thing that is a mistake I've found several times trying to help someone with "brake issues".... Not every M/C is the same line configuration - i.e., some M/C's run the front reservoir to the fronts and some run the front reservoir to the rear.

79 Vette masters are equal size reservoirs.
Several guys on Nastyz28 have used this with success this way too.
So I'm not guinea piggin it.

[Hydratech®]

If all else fails, you may have to get into port plug diagnostics. Even though this article is written for hydroboost applications, the basics still apply to a manual or vac assist brake package: http://hydratechbraking.com/Hydratech/braketech1.html

For instance, you could plug the ports at the rear axle flex hose, obtain a good pedal, THEN connect one rear caliper at a time, bleed it out and see what you've got. Since this axle was handled / transported, it strikes me that you may even be fighting an ever so slightly tweaked caliper mount bracket (that could've been thumped while wrestling the axle around).