Activating reverse lockout to bleed surge brakes

[jlastofka]

I had to replace a caliper assembly and I decided to replace all my brake tubing with a Tie Down Engineering flexible line kit. When it came to filling and bleeding the system, I couldn't get fluid to flow. I tried a few different vacuum techniques and a couple pressure systems. No luck. Finally, I decided to activate the reverse lockout solenoid and try it. Seemed counter-intuitive to me, but nothing was working, so ....

It worked !!!

I see now there's another port on the valve and I've read online that these are special valves for these brake systems and they're made to bleed any residual pressure in the lines back to the reservoir when the solenoid is activated. I haven't studied the system or thought through it carefully, but at least I'll be able to finish the project tomorrow, most likely.

Am I the only one who didn't know that the solenoid had to be activated to bleed the brakes? I've searched our site and others and no one's mentioning it. I also didn't find it in any instructions I've seen yet.

Maybe it's late and I'm tired.

-Jeff

[jlastofka]

Oh. Sitting here watching a movie I was thinking and realized the valve is simply a "Y" valve. In the normal position the wheel cylinders are connected to the master cylinder and when the solenoid activates, the wheel cylinders are fed back to the reservoir instead. Duh. Very simple.

I just expected (previous to all this) that the solenoid valve simply blocked the line between the master and wheel cylinders.

The three way connection with the bleed back to the reservoir makes a lot of sense, now that I see it.

-Jeff

[jlastofka]

In summary:

I'm now connecting a positive pressure fluid tank to the stainless bleed fitting at the wheel and pushing fluid all the way through the reservoir and out a custom cap I machined to mount a hose going to a catch tank. The hose is suspended over the tank so I can see a solid stream of fluid exiting. With the solenoid "off" I'm trying to push fluid into the master cylinder. With it "on", the fluid goes into the reservoir.

Also, I think some trailers have been sold with a simple blocking solenoid valve like I had assumed, but mine's got this better setup, which I now assume is the modern standard.

-Jeff

[Sneaks]

Oh jeeze, I had a brain fart and thought you were bleeding in the other direction. ie: pumping the master cylinder and not seeing fluid come out of the wheel bleed points.

As Gilda Ratner would say, "Never mind" (my PM)

Don

[jlastofka]

It took days of on and off messing around but I finally got my brakes working. I think the final trick was turning my excess brake hose storage loops horizontal to minimize the amount of up and down wandering of the hose going through the whole system. There's still up and down, but much more gradual than what the loops did.

It wouldn't purge properly before I did that. I tried two vacuum systems, a positive pressure system and manual two-person pump and wrench action. Nothing worked. What a struggle.

In the process I had my solenoid act up a couple times and I found crud floating around in the master cylinder, so I bought an entire new UFP actuator assembly.

-Jeff