Need some Brake advice???

[Jacob]

I will try to make a very long story short ... I have a complete kit with the standard issue brakes, Wilwood 3/4 inch cylinder for the fronts and 5/8 inch for the rear. After bleeding the brakes for two days I am certain there is no air in the lines. The front brakes are firm but the rears are not, I can push the rear cylinder in with my hand. I have adjusted the balance bar from one end to the other. Its like the rear master cylinder isn't holding pressure? I called Wilwood and they said with 3/4 in fronts and 5/8 rear I would never get a firm pressure at the rear, that I should have 7/8 inch master cylinder for the rear. I explained it was an FFR kit and he was very familiar with the deal and assured me I had the wrong size.

So I called FFR and they tell me I have the right size cylinders but that I'll need to bleed both the front and the rear at the same time? I told them what Wilwood said and the response was "we know what works best on these cars"...I wanted them to explain to me why Wilwood said I had the wrong size. Also told them I wasn't too happy with their answer...With no air in the rear line I cannot understand how I can easily push the rear cylinder in by hand, unless the master cylinder is defective?

Any input would be appreciated...right now I am going backwards on this build!

[Railroad]

I have the same size master cylinders in my kit. I would put more confidence in FFR. I am sure they want to avoid the rears locking up too easily.
On the soft rear master cyl, you might have a piece of trash under the check valve on the master cyl piston. Being a new master cyl I would not think it would be corrosion or sludge. You can make a couple of quick hard stabs at the brake to dislodge any possible trash. If you can move the bias more toward the rear master cylinder it might be more effective.
If you are confident you do not have air in the system, I would think your master cyl is by passing the pressure, bad seal or check valve. I have not begun to bleed my system yet. If someone still go carting with the same system can press on their plunger by hand, you might be able to make an assessment.

[Misterfubar]

I'm in the same boat. I just finished plumbing and bleeding mine and the rear seems awfully soft. Mine is a complete kit, but I'm using 13" Cobra front brakes and the 13" 2015 IRS rear brakes. The front is nice and firm and the rear pushes in very easily. I was going to try bleeding it again this weekend.

[Jacob]

I'm in the same boat. I just finished plumbing and bleeding mine and the rear seems awfully soft. Mine is a complete kit, but I'm using 13" Cobra front brakes and the 13" 2015 IRS rear brakes. The front is nice and firm and the rear pushes in very easily. I was going to try bleeding it again this weekend.

Good luck, if you figure it out let me know. After 2 quarts of fluid I am convinced beyond a question there is no air in the system.

[edwardb]

I don't know if I can solve your problem. But a couple comments. Too bad about the information from Wilwood. They do a lot of business with Factory Five. But obviously whoever you talked to isn't familiar with how Factory Five has the Wilwood setup installed in these cars. In this case, I would absolutely believe what Factory Five is telling you versus whoever answered the phone at Wilwood. With the Wilwood pedal box, for the first couple years Factory Five provided 3/4-inch master cylinders for both front and back circuits. For some time now, including my current build delivered in August 2015, they provide 3/4-inch for the front and 5/8-inch for the back. The reason is these cars need rear brake bias. The 5/8-inch master cylinder provides more pressure (not less) to the rear calipers and provides better overall braking balance. For the balance bar initial setup, I would recommend following the directions and set it up exactly centered between the two master cylinders, with the proper spacing as shown in the Wilwood instructions.

For bleeding, you're not the first to have trouble with that with this setup. Did you bench bleed the master cylinders? May not be necessary, but eliminates another potential issue. It's easy enough. One at a time, remove the brake line from the master cylinder and route a temporary line to the open top of the reservoir. Pump the brake pedal until you get a solid flow of fluid. This removes air from the master cylinder and also verifies that the master cylinder is pumping fluid as it should. Do the same for both. Hopefully you will see both master cylinders working properly. You might get a clue about a defective master cylinder in this step. Assuming that works OK, then re-attach the brake lines and do the normal bleeding process. The conventional sequence is farthest to closest. Rear PS, rear DS, front PS, front DS. You may want to try doing two at a time as Factory Five suggests. I've heard more than one say this worked and solved their problem. For my build, I did pressure bleeding with a pressure cap on the reservoirs. I've used that method for all my builds, including the Wilwood pedal box, and always have a hard pedal the first time.

If after these steps you still can push the master cylinder in by hand, something might be wrong. Defective master cylinder is a possibility.

[Jeff Kleiner]

...Did you bench bleed the master cylinders? May not be necessary, but eliminates another potential issue. It's easy enough. One at a time, remove the brake line from the master cylinder and route a temporary line to the open top of the reservoir. Pump the brake pedal until you get a solid flow of fluid. This removes air from the master cylinder and also verifies that the master cylinder is pumping fluid as it should. ..

Paul has given you good advice here. One clarification in case you aren't familiar with the process---the open end of the temporary line needs to be submerged in the fluid in the reservoir.

Good luck,
Jeff

[CraigS]

Bleeding one front and one rear at the same time really does help. My take on why is this. The 5/8 MC will need more pushrod movement to actuate the brakes than will the 3/4 MC. When you bleed just the 5/8, you will notice that the balance shaft takes on an angle when viewed from the top because the 3/4 isn't moving. I believe that at some point that angle prevents the 5/8 pushrod from going to it's full travel all the way into the MC. So you never get a complete stroke of the 5/8 MC. Bleeding both a front and a rear at the same time allows both pushrods to go all the way into their respective MCs so you have a better chance of getting all the air bubbles to move out of the MC. If you don't have a pressure bleeder I recommend two friends. The problem I have had w/ bleeder bottle and a one man operation is that the fluid gets pushed into the bottle just fine but, when you release the pedal, air can get sucked back into the caliper because the bleeder screw threads are not well sealed. W/ your friends keep using two bottles but this is my technique. Man in driver seat (pumper) says 'pumping' and pumps the pedal maybe 6 times and then holds pressure on the pedal and says 'holding'. this lets his friends know they can open the bleeders and they say 'opening'. As the fluid flow slows (don't wait for it to stop completely) each friend closes the bleeder and says 'closed'. Now the pumper can say 'pumping' and do it all again. All this talking seems a bit weird at first but it will make sense as soon as the pumper starts pumping while one of the bleeders is still open. Yes that will inadvertently happen somewhere along the line. If you want to make a pressure rig, this is what I bought
http://www.ebay.com/itm/NORGREN-R73G...QAAOSwiONYOgoO
Found a short piece of radiator hose that slipped over the reservoir opening, got a couple of fittings at the hardware store to put in the other end to neck it down to 3/8 inch air hose size. 5 feet of air hose so the regulator can sit on the floor, and a couple of quick connect fittings to plug the regulator into my air supply hose. This will regulate down to <5# but I bleed at 5#.

[Jacob]

thanks all for the info...I'll try these suggestions and get back with how it plays out. At least now I know I have the right sized masters, thanks Paul B and BTW congrats on your 1st place, well deserved!!

[Jacob]

I took the rear master cylinder off and bench bled it ( I had not done this initially). There appeared to be a pretty good amount of air that was purged out. Plan is to hook everything back up and try again. My guess is that all will work ok and that air in the master was my problem...we'll see?

[edwardb]

I took the rear master cylinder off and bench bled it ( I had not done this initially). There appeared to be a pretty good amount of air that was purged out. Plan is to hook everything back up and try again. My guess is that all will work ok and that air in the master was my problem...we'll see?

Good luck and hope it works out for you. Just FYI, "Bench bleed" is kind of a misleading term. It's not necessary to actually remove the master cylinder to do the bench bleed. It can be done in place after it's mounted. In fact, that's what I prefer to do. The less I have to handle brake fluid, the happier I am.

[Jacob]

I hate brake fluid!!!

[jsteve5050]

Jacob, Did the bench bleed work for you, I am currently having a similar problem with a different master cylinder though.

[Bob Cowan]

I highly recommend Russell Speed Bleeders. You have to buy 8 of them for the Wilwood calipers. But it makes this a quick and easy one man operation.

As said above, with dual masters, you need to bleed front and rear calipers at the same time. Otherwise you'll never get a full stroke on the rear MC.

[BB767]

I struggled with this problem same as you and could not fix it, UNTIL I did the pressure bleed. Wonder why Edward never has a problem with his? Pressure bleeding! With mine, for some reason, during normal bleeding, air would enter into the master cylinder when the pedal was released. This would then be pumped into the lines creating an endless stream of bubbles and brakes never getting firm. A few minutes of pressure bleeding and the air went away and they firmed right up. Do it as instructed here though, DO NOT over pressurize the system.

[JoeAIII]

Back when I was tracking my last car often, I would bleed the brakes after every event. I picked up a motive power bleeder that made it super easy to bleed, even after replacing master cylinder or calipers, or the time,I broke a line and had to leave it open for days (all the fluid drained out of the system)
The power bleeder is portable and easy to use. When the time comes in my build I plan to pick up a new one.