Bleeding brakes?

[Fletch]

For those of you that are SAS'd...

I'm in the process of bleeding the brake system, and I can't seem to get a firm pedal feel, even after going through 2 quarts of brake fluid, and using a Snap-On air bleeder...

I actually get a firm pedal feel when the truck is not on, but when I fire it up, the pedal goes to the floor.

I still have the stock master cylinder, have stainless braided lines, and I'm running Wilwood calipers with a slightly smaller piston than the stock Dana 44 calipers, which should improve the pedal stroke over the standard Dana calipers....

Should I get a buddy and bleed them the old fashioned way? Or do i just need to run more fluid through the system? I bled every corner, starting with the wheel fartherst from the master cylinder. (right rear)

Any other suggestions?

[Packman5280]

i had a buddy help me, the air bleeder didn't seem to work that well. maybe i just did it wrong. once i had a friend help, it was much better.

[tmorgan4]

If you pump the pedal a few times with the engine off, you shouldn't be able to compress the pedal much at all. What technique did you use to bleed them by yourself? Probably just putting a line from the bleeder into a bottle of brake fluid? Always had success with that myself.

My very first thought when reading this was that your master is too small for the calipers but it looks like you already thought that one out. What calipers are you running, and how much bigger are the pistons than the stock calipers?

[Alex Topousis]

1980's corvette master is your friend here. I mean think about it, the nissan master is for less than 1/4 ton brakes and you moved up to 1/2 to 3/4 ton brakes

[Chainsaw]

Originally Posted by Fletch

I still have the stock master cylinder,

Originally Posted by Alex Topousis

1980's corvette master is your friend here. I mean think about it, the nissan master is for less than 1/4 ton brakes and you moved up to 1/2 to 3/4 ton brakes

All of this is the biggest problem, also did you bench bleed the MC? Even if its been in the truck if the fluid was all able to run out it needs an in the truck bench bleed to get all the sir out of the cylinder.

[Fletch]

Still using the stock master cylinder, and I only unhooked each of the front lines long enough to swap the new hoses and calipers in. The master never came close to running dry.

I'm using these calipers from Wilwood. They were a direct bolt on:

http://www.wilwood.com/Calipers/Cali... Single Piston

Specifically, I ordered the ones with the 5.94 " piston area. I calculated the piston area of the stock Nissan dual piston calipers, which came out to be 4.81". So the fluid volume required by these calipers is only slightly higher than the stockers, which is a helluva lot better than the 7.07" piston surface area of the stock Dana calipers. I'm going to switch to a larger Chevy master cylinder as back up, but I know guys that are running the big Dana calipers and the stock Nissan M/C and the pedal travel is nowhere near this bad.

I've been using an older version of this air bleeder from Snap On:

http://buy1.snapon.com/catalog/item....re&dir=catalog

I've noticed after using the air bleeder that the vacuum from the bleeder is sucking the piston back into the caliper slightly... In other words, fluid seems to be gettiing evacuated faster than it can run through the master cylinder down through the lines. So I've been pumping up the brakes before I move on to the next wheel. But as I said, i've already run 2 quarts of brake fluid through the system using this method. You would figure the air would have been eliminated by now.

[Bill Potter]

Ditch the air bleeder and build your own bleeder bottle. The air bleeder will suck in air making everything a pain in the ass.

Get a used clear water bottle and 6-8 feet of rubber hose that matches the nipples. (it needs to be long enough that you can set the bottle in a place where you can watch it while pushing on the pedal)

Drill a hole in the water bottle lid the OD of the rubber hose. Stuff one end of the hose to the bottom of the water bottle and hook the other end to the bleeder valve. Set the bottle upright where you can watch it. Crack the valve and start pushing the pedal until it can be pushed with out any air bubbles making it to the bottle...then push it 4 or 5 more times. Remember to top off the MC every 10-15 pumps.

Also if you have drum brakes in the rear it is highly important that they are adjusted correctly before you start. The drums should be slightly rubbing the pads when you put them back on. The looser they are the more fluid it will take before the pedal starts to feel stiff.

[itsme1738]

i agree with bill

[Houdini]

do it the old fashioned way with a buddy for the best results. i've ran several qts through my system before and still they don't feel solid until i get a helping hand and do it the correct way.

[Fletch]

Well, I did the empty water bottle method last night with yet another full quart through the system, with no improvement. I'm beginning to think that maybe I do needd to bench bleed the master cylinder. My truck has 150,000 miles on it. Could it be that the piston seals in the master cylinder are shot? It was working fine with the stock brakes when I parked it in January. Maybe 6 months of inactivity just finally caused the seals to give up the ghost?

I'm going to try bleeding the master cylinder, and then I guess it's on to a new master cylinder if that doen't work. When I bled the system last night, there wasn't a single air bubble coming through that hose...