Filling and Bleeding Hydraulic Brakes

[Tim Smith]

Hello.
I have Tracy Obrien hydraulic brakes and a stick mounted master cylinder. I am trying to fill and bleed them, and generally making a frustrating mess of it.
Any suggestions on how to do it, and a set up that will get more fluid in the system and less on me?
Currently trying to use a 60cc horse syringe, 1/4" tubing safety wired to brake bleeder, pumping fluid up to master cylinder, working master plunger and bleeder valve to purge air. Master cylinder hanging free.
Keep introducing air bubbles at wheel bleeder/ tubing connection. I am pretty sure someone has successfully done this before.

[Waiex 49]

Hi Tim,

I don't have the TOB brake system but I recently experienced the "fun" of bleeding my Sonex disc brakes and the dual Hegar master cylinders.

I put grease on the threads of the bleeder valves and this stopped the air leaks.

I made a bleeder system using a pump style oil can fitted to a length of clear plastic flex tubing and at the other end I had another length of tubing going into the top of a small jar. I could pump fluid into the system and capture the fluid coming out the other end. I did all the bleeding on my own without an assistant.

It wasn't easy to get all the air out, especially on the vertical sections of tubing on the gear legs. I had to bleed the system both ways. That is, I bled it both "top down" and "bottom up" to get all the air bubbles out of the lines.

Keep your cool and be patient. You will be happy with the results. Having decent brakes is a good thing. I am so glad I made the decision to get rid of those wimpy ass Sonex drum brakes!

Don Bowen
Viking Waiex N49YX
KLHM

[fastj22]

Here's the way I bleed my Hegar brakes.
I have an old school hand oil pump can, the kind you fill with oil and squirt it on stuff by squeezing the trigger. I fill that with fluid and put a rubber hose on the tip to connect to the nipple on the bottom bleed valve on the wheel. On the hagar end (top side) I have a small empty water bottle with hole drilled in the cap for a rubber hose to slide in and connect to the nipple on the master to that hose.
The process is to connect the pump on the bottom, open the valves and squirt fluid until you get all the air out at the top and fill up the catch bottle. Then close the valves. You can then fill up the pump with the catch bottle contents.
There are fancier brake bleeders out there but this seems the best I've found.

[DCASonex]

Just to further what fast22 posted: Have similar brakes and use very similar method. No reservoir on mine so do this couple of times a year. Working alone, takes about 15 - 20 minutes for the two independent systems, no mess. Avoid using any fitting in line between caliper and actuator cylinders (including firewall fittings) unless arranged vertically so as not to trap air. Actuator cylinder must be positioned with its bleeder at high end. Pumping fluid continuously from oil can type pump pushes out air from horizontal and short vertical runs, where as when pausing to refill smaller supply, lets air flow back.

David A. Sonex TD, Differential toe operators with Great Plains brakes

[kmacht]

I have the same Tracy-Obrien setup. As said earlier, pack some grease around the bleeder valves on the brakes. This will keep it from sucking air in around the threads and hose while you push the fluid up towards the hand brake. A slightly undersized hose that is warmed with a hair dryer and pressed on the bleeder fitting also does wonders to keep air from seeping in at the fitting. The other thing you need to remember to do is to flip the hand brake master cylinder upside down when bleeding. If you don't you will end up with a large air bubble inside the master cylinder since the bleeder is on the bottom.

When I did mine I bled them both in both directions. I did the initial fill and bleeding by pushing fluid from the bottom up. After I thought I got all the air bubbles out I went and did a second bleed pushing from the top down. I found a few small air bubbles during the second go-around probably from inside the master cylinder. Bleeding is a two man operation. You only want that bleeder screw on the master cylinder open when pushing fluid. As soon as you stop pushing it needs to be immediately closed so you don't suck air back in. The good news is that I haven't had to re-bleed them in 2 years now. The system seems pretty leak proof once everything is tightened up.

Keith
#554

[vwglenn]

All of the above. Make sure your catch bottle is higher than whatever bleeder it's attached to and the end of the hose in the bottle is sitting in some fluid. That way it will push out the bubbles and, if it draws back, it will draw fluid instead of air. Also make sure you have enough fluid in whatever container you're using to feed the fluid. If you run out before you're done, you'll have to start over.

[tljones42]

When I filled the Sonex hydraulic brakes (from the bottom) I kept getting a tiny bubble when I pumped the lever a few times after the reservoir was full. Couldn't seem to get rid of those no matter what I tried. Talked to a local hydraulics guy who said they normally prefilled the cylinders but I didn't see a way to do that. He then suggested that I change the angle of the reservoir to try and release air which was apparently trapped in the cylinder. I did that by pushing the tail of my tri-gear down onto the skid. That solved the problem.

Tom Jones
Onex 0133