gravity brake bleeding

[huffmuds9320]

I recently bleed the brakes in my 02 VW Jetta and noticed the brake pedal feels softer than before. The method I used was the 2 person method where one pumps the brakes and one opens the bleeder. I made sure to check the fluid level. The only thing I may have done wrong is the clear tubing was not snug on the bleeder. Its hard to get the tubing to stay, keeps popping off.

I wanted to know if there are one person methods without the use of pressure bleeder or vacuum. I have never done the gravity method where you open the bleeder and let it drip. Not sure if thats a good idea. Any suggestions welcome, thanks.

 

[CBDFrontier06]

It seems to me just opening a valve and letting it drip would be an open invitation for air to enter the system. I don't recommend that.

If your pedal is soft, it may be from releasing the brake pedal before the valve was closed. That's the best way to suck a line full of air. In my experience, the pedal always got firmer after bleeding. Hate to say it, but you may be in for another round of bleeding.

 

[moribundman]

Originally Posted By: lpcmidst128
I wanted to know if there are one person methods without the use of pressure bleeder or vacuum. I have never done the gravity method where you open the bleeder and let it drip. Not sure if thats a good idea. Any suggestions welcome, thanks.


I don't think gravity bleeding by itself will work sufficiently on all cars. I combine the pressure bleeder with pumping the pedal two or three times per caliper. Works fine.

 

[George7941]

Gravity bleeding works well with trucks which have larger brake lines(1/4 in ateel tubing) and, because of the height of the vehicle, more pressure(measured in inches of brake fluid column) pushing the fluid out. There is absolutely no risk of air entering thru the bleeder valve because of the positive pressure there. I have bled many a truck this way and never had a problem.

With cars, gravity bleeding may or may not work. The way to find out is to open the bleeder and see how well the brake fluid flows out. If there is continous flow, no matter how slow, then you have continous positive pressure and no air will enter. However, if the fluid is coming out in drops, then there is the risk of negative pressure leading to air entry.

 

[BarkerMan]

I have been using the Griot's Garage brake bleeding vacuum system with great results. I like the little bottle you stick in the master cylinder res that keeps the level right on the MAX mark.

 

[Kestas]

I've had success using a one-man bleeding system where you attach the tubing and only crack open the bleeder a bit. When you press the pedal down, the high pressure will force the fluid out, yet choke the fluid flow for the reverse stroke where there is less pressure to draw it back in. Works for me quite well.

 

[TooManyWheels]

I have done pure gravity bleeding on a vehicle which was otherwise difficult to bleed with very good results. In other cases I have hooked a brake fluid filled drip system to the bleed screw, - the idea being that the fluid weight from two directions will displace/replace the trapped air. If the fluid bottle had an air bleed you could also use this setup while pumping the pedal.

 

[Spitty]

I have bled many Brake systems over the years, the last was actually an 03 Golf. My system is to use about 1 ft of surgical rubber tubing (You get it at Hardware stores for Sling Shots etc.) Make a small, longitudinal slit in the tube with a Razor blade, about 2" from one end (the slit will act as a one way valve) Then Plug the end with a small bolt. Push the other end of the tube on the Bleed Nipple, and hang the Bolt end in a catch jar (You can add some brake fluid to the jar to act as an additional Air Lock) Loosen the nipple and pump away! It is an idea to have someone watch the Jar for Bubbles or rig up a Mirror.

 

[rpn453]

I bought a vacuum brake bleeder kit for $25 at Princess Auto(Canadian). I needed to buy some smaller diameter tubing to get a tight fit on the nipple, but once I did that it worked great.

 

[huffmuds9320]

Thanks for the replies. Sounds like the vacuum method should work out and its simple. I'll just buy that vacuum bleeder kit and redo the brake bleeding.

 

[moribundman]

Don't forget to gently rap on each caliper while bleeding. This will loosen air bubbles that might otherwise remain in the system.

 

[Audi Junkie]

Let's just cease the whole "pumping" the brakes thing. Pushing the mc seals beyond the normal range of travel abrades them against the worn lip of the cylinder bore. That's an invitation to destruction.

I'm not telling anyone to do it my way, but I routinely let the brake system run dry and then refill it. I'll leave the bleeder screw open a crack as I move along the car doing the gross bleeding without any pumping, at all. By the time I get back around to #1 bleeder, they are blead fine. Rapping on the caliper like Mori said helps.

I'm not a fan of bleeding in between pad changes. When you do pads, yes definately bleed them fully and tweak the calipers themselves, but that going to a dealer or shop to bleed them on a 2-year schedule is total sillyness and might be bad if they pump things or introduce contaminates. Plus, unless you depress the caliper cylinder to clear the old fluid from there, it's pretty pointless to do just the lines.

 

[mechtech2]

Gravity bleeding is slow but works well.
Sometimes it's the only option.

 

[moribundman]

Originally Posted By: Audi Junkie
Let's just cease the whole "pumping" the brakes thing. Pushing the mc seals beyond the normal range of travel abrades them against the worn lip of the cylinder bore. That's an invitation to destruction.


Nowhere did I suggest to push the pedal all the way beyond the normal range! Apparently common sense isn't common any more.

 

[Kestas]

I've tried vacuum bleeding many times on many cars. 80% of the time I draw air past the bleeder threads and get horrible bleeding action. I've abandoned this method.

 

[johnd]

Quote:
I've tried vacuum bleeding many times on many cars. 80% of the time I draw air past the bleeder threads and get horrible bleeding action. I've abandoned this method.


I'm with him. I have a Mityvac and I never did have any luck with that method. Years ago I bought a kit in a parts store that was a piece of vinyl tubing with a one way ball valve on the end. Still have it, still works. Worst one I ever did was a Toyota truck that had the bleeder not at the highest point. We finally took the caliper off and bled it with the bleeder straight up and it finally got all the air out.

On another note, people will often tell you when putting in new pads to suck fluid out of the master cylinder so that it won't run over when the fluid is pushed back into the system by the piston. The last thing I want flushing through my ABS unit is old brake fluid. I put a hose on the bleeder and open it so that the fluid drains out of the system when I compress the system.

 

[PT1]

Originally Posted By: Audi Junkie
I'm not telling anyone to do it my way, but I routinely let the brake system run dry and then refill it.


This has always worked well for me. Get ALL the old fluid out first then flush any residue with new fluid. Takes an extra can but seems to stay clean longer. I too only bleed the fluid at pad replacement.

 

[huffmuds9320]

When I did the 2 person method, I placed a dumbell (or wood block) on the floor so you can't press the pedal it all the way down. Of course make sure to take that out when you are done.

 

[The Critic]

Originally Posted By: PT1
Originally Posted By: Audi Junkie
I'm not telling anyone to do it my way, but I routinely let the brake system run dry and then refill it.


This has always worked well for me. Get ALL the old fluid out first then flush any residue with new fluid. Takes an extra can but seems to stay clean longer. I too only bleed the fluid at pad replacement.

Except if you run the ABS unit dry somehow, you're screwed. You'll need to bring it to the dealer to bleed it as it requires a dealer-only scantool usually.

 

[benjamming]

Will activating the ABS move the air through the system so that when you bleed the brakes it is removed?