OCDHerb

I have removed renovated and reinstalled the entire brake system. Unfortunately the aren't working. I've bled them to the point where no bubbles appear but the pedal still goes to the floor. No leaks. I rebuilt the original master cylinder first but have since replaced it with a new one without improvement. Need sage advice.

Herb

t_g_farrell

iTrader: (1)

Details on pedal goes to the floor, engine running or off?

You have a 78, err 79, but SA anyway.

Did you bleed the master at the bleeder on the side of the master?

When you bled the brakes how many pumps did you do on average for each wheel would you say?

What was your method for bleeding?

Why did you not trust the rebuilt master and get a new one?

TomSmy

iTrader: (11)

Did you replace the brake booster?

If so, is the push rod set to the correct length?

Tom

LongDuck

Are you getting any leaking brake fluid from any of the calipers? If it's sealed up tightly, then it could be something as simple as a Master Proportioning Valve which isn't working correctly which is letting the line pressure bypass the valve piston. When that occurs, you won't get any pressure to any calipers because it's lost back into the reservoir.

I would focus your testing and efforts on the Master Cylinder right now, as your bleed procedure at the wheels is pretty straight forward. I've not had good luck with rebuild kits for it, but the factory rebuilt versions seem to be pretty consistent for the 2-3 I've replaced over the years.

DreamInRotary

iTrader: (49)

Did you remove anything you haven't mentioned here? Swap any of the braking components for an upgrade or anything? Seems very weird that your pedal would still go to the floor with completely redone brakes.

TomSmy

iTrader: (11)

Also as an FYI, I had a similar issue and it turned out that the brand new master was faulty....

If your old one worked, it may pay to put it back on to at confirm or eliminate the master as the issue. It would have saved me a lot of time if i had done so.

Tom

OCDHerb

I rebuilt the original and installed it first then installed a new (remanufactured) master. Symptoms are the same so fairly certain it isn't the master.

OCDHerb

[QUOTE=t_g_farrell;12223285]Details on pedal goes to the floor, engine running or off?

You have a 78, err 79, but SA anyway.

Did you bleed the master at the bleeder on the side of the master? Yes

When you bled the brakes how many pumps did you do on average for each wheel would you say? 5ish

What was your method for bleeding? Open, Press, Close, Release, Repeat (until no bubbles in jar).

Why did you not trust the rebuilt master and get a new one? I was getting the same results. Pedal was going to the floor.

GSLSEforme

Are your rear brake shoes adjusted properly? Are you getting even fluid exchange with volume at brakes front and rear/ Believe you have bleeder on one wheel cylinder in that early a car? Some thoughts,suggestions... Master cyl./booster pushrod adjustment correct? I realize everyone doesn't have access to professional brake bleeding equipment... my personal favorite way to bleed brakes-especially from a bone dry system is to use a Mityvac bleeder. Fill the master cyl.reservoir with fluid, start at farthest bleeder from master cyl.,hook Mityvac hose nipple to bleeder,open bleeder. Mityvac pulls a vacuum on system,pulls all air out which draws brake fluid from reservoir and fills all voids in system that previously had air. You know it has when brake fluid comes out of hose to Mityvac. Top up m/cyl. reservoir as fluid is taken into system and work your way around to closest bleeder to master cyl. When done there will be no more air in system,brake pedal will be 100%. This is what i'd do in your situation if i didn't have access to the above mentioned equipment. You'll want to open all bleeders(with the exception of the one on master cyl.) slightly,enough that brake fluid can drip from each. I know you have freshly painted surfaces everywhere and certain you don't want brake fluid to damage them. Fit a length of vacuum hose to each bleeder long enough to loop down to just above a container you'll set beneath for the fluid to drip into and let the fluid drip for as long as it takes,hour(s) overnight, til you have a steady drip coming from each bleeder. Be sure to keep reservoir topped up. Close bleeders when you have had steady drip for 20 mins. or so. This is called gravity bleeding and works fairly well and is followed up by regular bleeding with an assistant. Some recommendations: at this point not necessary to pump pedal more than three times before opening each bleeder. (start with farthest away bleeder) It's worth mentioning here you want the pedal pumper to slowly pump the pedal and slowly release the pedal before pumping again after bleeder is closed,you do not want to pump pedal quickly as this foams the brake fluid and you're letting air back into the system as the air is suspended in the fluid as yo're bleeding it thru. This could be what is happening here. Also rap calipers,wheel cylinder areas on backing plates with a rubber mallet just before you open the respective bleeder,this will loosen possible air bubbles and move them along as you bleed the system.

GSLSEforme

If after all this exhaustive bleeding you've made no progress,time to go back and diagnose each component and section of brake hydraulics by isolating each part of the system. Start with the master cyl. If you have some old sections of brake line with a fitting and a flared end on tube you can make a hydraulic plug from it. Cut the line an inch and a half or so behind the flared line/fitting with a tubing cutter, smash the last 3/8" inch of the line closed with a hammer then put that 3/8" section in a vice and bend over 180 degrees and smash again with a hammer. You now have a hydraulic plug,make two. Get a couple 3/16" vacuum caps handy,take precautions with painted surfaces(i use a spray bottle mixed 50/50 dish detergent and water. Spray this mixture all over painted surfaces around and in close proximity to where you're working. This breaks down any brake fluid even if it touches nearby painted surfaces). Remove both Brake lines from master cyl.,slide fitting back and slip vacuum caps over flared end of brake lines to keep fluid from dripping out and air from getting in. Some fluid will drip from master cyl while you're removing lines and before you can screw your plugs into m/cyl,have a slightly soaked towel to absorb and break down any fluid and place in.area underneath m/cyl. Snug fittings in place on m/cyl,top up with fluid, get your helper to push lightly on brake pedal with THEIR HAND as you crack loose slightly one of the fittings with a wrench cupping your hand with a towel around fitting so no fluid sprays out and gets on paint. Have your helper slowly push pedal to floor and not let up until you close fitting. You don't need to see the fluid coming out,you will feel it in your hand with the towel on it. Now bleed the other side of m/cyl the same way. Should not reguire more than two strokes for each side to bleed it. You should have a rock hard brake pedal with no more than1/4" of play,if you don't you have fluid leaking by seals in a defective master cylinder. If m/cyl tests good,quickly remove your plug and vacuum cap and install your front brake line to m/cyl and bleed front brakes by hand just as with the m/cyl. You should be able to feel the pedal by hand,should be at least 3/4 of pedal with very little travel. If you have that,hook up rear brake line and bleed rear brakes by hand. Should have a decent pedal by now,may want to go around once more bleeding with foot pressure to be sure all air is out and pedal is good. Rinse off all soapy water and blow dry with air so you can look for possible leaks. Hope this helps.

TheRX7Project

iTrader: (3)

Did you bleed the master before or after you bled the wheels? Bleed each wheel THEN bleed the master LAST, and I almost guarantee the brakes will firm up. I had the same thing recently when I did the lines on my '80.

Also, you need 2 people to properly bleed the brakes, have person 1 pump 3 times and hold, then person 2 cracks the bleeder, closes the bleeder, then person 1 can release. That passenger side rear line can be a real bastard to get the air out of.

OCDHerb

The brake pedal is now hard but the pedal travel is longer than I remember. I checked the adjustment under the dash. It looks reasonable. I did install a new brake booster. Is there an adjustment in that for travel?

Herb

TomSmy

iTrader: (11)

Did you adjust the push rod on the booster before attaching the master?

Too short and pedal travel will be increased, too long and your brakes will drag

GSLSEforme

^^^^ this and proper adjustment of rear brake shoes is integral with achieving a good pedal. Curious as to your solution for the now hard pedal.

TheRX7Project

iTrader: (3)

I couldn't believe the difference it made when I adjusted my rear brakes, not just in pedal but in overall feel of braking. Someone (I want to say it was KansasCityREPU) suggested making them "just barely drag" and that's what I did. Tremendous difference.

t_g_farrell

iTrader: (1)

For any drum rear brake RX7s this is a requirement. Also remember if you have auto adjusters, that they usually don't, so manually readjust every 5K miles to keep the brakes feeling good.

Not sure how much it makes a difference on the rear disc brake setups.

GSLSEforme

Rear disc(GSL) brakes are win win,really no negatives. The initial "adjustment " is just like front discs. When new pads are fitted the pistons are retracted into the bore,after caliper installed,pedal is stroked to bring pads out and in contact with rotor. The pedal feel and position will not change as brake pads wear as happens when brake shoes wear and need to be adjusted to maintain pedal. As disc pads wear,pistons move out of caliper bore keep pad in contact with rotor. As pad moves out,brake fluid from master cylinder reservoir takes up void where piston was so brake action,response,pedal feel remains the same. Disc brakes are inherently more efficient and run cooler as a result of how much of braking surface is exposed to cooling air. One of reasons SE model has best brakes of all 1st gens- bigger and ventilated rotors all around.