No Brakes

[pearsonbe]

The brake pedal sinks to the floor with little resistance. I noticed the master cylinder was leaking at the brake booster so we replaced it today. However, we could not bleed it because there is still no pressure in the pedal. I replaced the rear lines (hard and soft) a couple of years ago and they don't appear to be leaking. I also don't see fluid leaking at any of the wheels or in the lines under the truck. The section of line to the rear that passes over the tank couldn't be seen. I did not remove the wheels to inspect. With the lines tight at the master cylinder, I also had my son pump the brakes while I looked around the truck front and rear over and under. I didn't see any fluid leaking or dripping.

Tomorrow, I will try to move the truck into the garage and remove the front wheels to get a better look. By the way, I just got the vehicle back from the shop. They replaced the fuel pump, filter, and part of the hard lines. They recommended replacing the master cylinder, front backing plates, calipers, rotors, and pads.

 

[Anime]

Did you bench bleed the master cyl before installing? If no, it could take quite a while when bleeding the brakes to get enough pressure on the pedal.

Also be sure you are bleeding using the recommended procedure - start with the longest line (passenger rear), then move to the driver's side rear, passenger front, driver's front, and keep going in that sequence until all the air is out, and the pedal is firm.

It's pretty common when installing a new master cyl (or any hydraulic part, really), even when bench bled beforehand, to have it take awhile to build up pressure in the system.

Usually a way to speed this up is to use a vacuum pump to pull the fluid down and extract as much air as possible that way, then there is usually pressure after a few bleeding rounds.

 

[pearsonbe]

We couldn't find a tool locally to bench bleed the master cylinder. And the new one didn't come with one. It included colored plugs but I can't see how they would help.

I was told we could bleed it while installed on the vehicle. The procedure is to install both lines, crack one, push the pedal to the floor, close the line, release the pedal, and repeat until no air is visible. Both lines should be done that way. But we never got pressure. Spent maybe 15 minutes doing that before I started looking for leaks.

I will look for a bleeding tool online.

 

[Anime]

You don't need a "bleeding tool" to bench bleed a master cylinder.

Just connect a fitting and hose long enough to go back into the reservoir to one outlet (if the others are already plugged) and add fluid to the reservoir, then push in the piston about an inch or less with a wooden dowel or whatever won't harm the piston, and repeat until the fluid comes out without air bubbles.

You can even attach fittings and hoses to all the outlets at once.

It can be tricky to get the brake lines attached without the fluid leaking everywhere and making a mess when installing, but usually you can get the bleeding fittings loose, and pop them out and the vehicle fitting in with minimal leakage that you can catch with a basin and towel or rag.

Otherwise you can get a vacuum pump to try and pull more fluid into the master cyl before bleeding on the vehicle.

You may have to manually pump the piston with the pedal, pulling it out (being sure the reservoir is full each time so it's not sucking in air), until it builds up enough pressure to return on it's own. If you just push the pedal down then pull it back without filling the reservior, air keeps getting into the system and you'll never bleed it that way.

 

[914jaloppy]

Living in CT sucks....They use the Liquid Crap on the streets and it is eating thru all our brake lines at an alarming rate. Yet they refuse to do anything about it.
My original lines (everything)were replaced in 2007. That's 16 years of blissful use....
In 2012 I had to replace the line that ran up and over the fuel tank. That is only 5 years of blissful use. Five years. I'm sure I will be replacing another one this year.
If you live in any State that uses Calcium Chloride and/or other chemicals, check under your vehicle! Look at everything.....here's an article.

http://machinedesign.com/archive/news-about-road-salt-worse-we-thought

I'm sure you all know of this already, but it's coming to that time of year again,, keep the underneath of your vehicles as clean as you can!!!

Good Luck!

 

[pearsonbe]

Thanks, Anime. I decided to buy the $13 plastic syringe by Cardone. It got great reviews and can be used while the cylinder is installed. That will save me time removing and reinstalling. Should be less messy.

I live in Md an we have issues with road salt too. Don't know if its the same stuff used in CT.

 

[pearsonbe]

Still working on the brakes. The bleed tool worked well. It only took a few minutes. Took me longer to remove and re-install the cylinder. There wasn't enough room to do it while mounted to the booster.

After pulling the front wheels, I saw that the calipers were in bad shape and replaced them with new pads. Started bleeding the system last weekend and continued today. It's taking a while. I need one of those vacuum pumps Anime mentioned.

The pedal is pretty firm with the engine off on the first press. By the second press, it is rock hard. However, it is still mushy with the engine running. Made a few rounds bleeding until I didn't see any bubbles, but it still aint right. I will try again tomorrow when my assistant can help. I feel like there is air trapped somewhere.

 

[pearsonbe]

Made several more rounds of bleeding today, but the pedal is only slightly better. I managed to get all the lines done except the driver rear wheel. I bled it many times, but air is still coming out. One thing I noticed is that the air starts to appear near the end of pedal travel. At the very bottom there are a lot of bubbles. What does that mean?

I checked the connections at the master cylinder and each wheel. There are not visible leaks and no fluid anywhere on the garage floor. This is very frustrating.

 

[natenkiki2004]

When I bled the front after replacing the hose, I noticed that the pedal had to be pumped vigorously as the air bubbles would only slowly come out with slow but consistent pumping. A few vigorous pumps later and it was solid fluid.

 

[pearsonbe]

Thanks. So the engine was off and the bleed valve closed at that wheel. You pumped the pedal vigorously then cracked the valve open to release the bubbles? Was the front of the vehicle raised?

 

[the_don]

Do you have ABS brakes?

 

[natenkiki2004]

Thanks. So the engine was off and the bleed valve closed at that wheel. You pumped the pedal vigorously then cracked the valve open to release the bubbles? Was the front of the vehicle raised?

Engine off, yes. I did not open/close the bleed valve with each stroke of the pedal, or build up pressure beforehand. To do this, you just need fluid in the container that you're pumping into. It's highly unlikely that fluid/air will travel back up the line and back into the system when the pedal is released. Still, better safe than sorry.

I opened the bleeder valve and had my helper pump the pedal vigorously then once the fluid was clear and bubble-free, I had my helper hold the pedal down on the last stroke (not to the floor, just don't let off) and then I closed the valve.

It's important to note that short strokes are good because when the system is open, it's easy to press the pedal too far. I've been told that when this happens, you're stroking beyond your normal range with a closed system and the engine running. This causes you to push past the normal wear area on the piston and if there's a lip created from the wear, pushing past that can damage the seals and cause internal leakage.

I raised each corner of the vehicle as I stuck my head and arms under to access. The vehicle was on a very slight slope, so slight that sometimes you wouldn't move backwards but the engine was pointed "uphill". That aspect doesn't matter though because the reservoir is well above any of the wheels and as long as the reservoir's lid is off, the fluid will flow through the system to the lowest point, which is the bleeder valves. The brake pedal just helps it get there faster.

 

[pearsonbe]

the_don, yes i do have RABS. i read that some vehicles have bleeder valves for ABS, but i haven't checked yet.

 

[pearsonbe]

your procedure was different from mine. the brake reservoir lid should be removed during the process? i thought i needed the cap to build pressure in the system. maybe that is my problem.

 

[pearsonbe]

Finally got it back on the road last week. The brakes are better than they were a year ago but not much. I tried bleeding again with the MC cap off but that didn't seem to make much difference. Even parked on an incline hoping any air would travel to the MC. Didn't help. I will probably take it to a shop soon.