Brakes - none... is this normal?

[LeoZelig]

I replaced the hard and soft lines for the front driver side today, starting with the truck on ramps. The double-flaring info on this site is great, by the way!

I had to pull it off the ramps to finish the job (long story) while the system was open, disconnected on that side. I thought, "Well, I still have rear brakes since it's a different resevoir, so even if I lose fluid through the open line, I will be able to stop."

Fortunately, I placed a chock about where I wanted to stop rolling in case I had a problem. Well, I did. The pedal sank to the floor and I had no braking.

The chock did its job, thankfully.

Is this normal?

Should the rear brakes have failed too, or is there something wrong with the distribution block (or somewhere else)?

I thought there was supposed to still be rear pressure.

If this is the way it is supposed to be, that doesn't bode well for a catastrophic failure on the road.

Also, since I disconnected one line from the block, should I bleed all four wheels?

Thanks!

p.s. I have drums on all four corners, and they are manual

[fordman]

since you had the ssytem open the rear brakes lost enough fluid via the dist block to not let the brakes work. the trip lever inside the block slide forward. and let the back brakes lose fluid. or redist the fluid to the front so the rear brakes failed. that my best guess. the ssytem is suppose to work like you say but only for a little while enough to stop once maybe. but the longer it was open the more it wouldn't work because of the redistribution of fluid to the open side. in other words they are all actually connected. and they just bled off while you were working on the system.

[ScreaminZ]

When one side of the system is open, the other side loses significant power, but will still usually work a little. Add to that the fact that your rear drums were likely out of adjustment. Combine those two things, and that makes for some real problems!

[Wes]

when one side has lower pressure the shuttle valve should be forced to the low pressure side. This normally takes 2 or 3 firm applications of the pedal. Either your fluid level was to low as Fordman suggested or the shuttle valve is stuck ie rusted. Yes you should bleed the whole system. It is good idea to flush out all the old brake fluid as well.

[FLATBEDFORD]

The front and rear circuits are isolated. The front and rear do not mix in the distribution block. I just had mine apart. As was said already, your rear brakes need some attention.

[LeoZelig]

Thank you Fordman, ScreaminZ, Wes and FLATBEDFORD for your help.

I will definitely check the adjustment on the rear brakes. At Thanksgiving I replaced the master cylinder, all four wheel cylinders, all shoes and some springs. I also did a major bleed and got a lot of nasty crap out of the system - the fluid is a beautiful amber, now.

I was also planning to replace all the soft lines at that point, but all three are rusted permanently to their hard line fittings. So this was the first of the three hard/soft line jobs I had left to do.

I did go ahead and bleed the whole system to be on the safe side. Fordman, fluid in the reservoirs was never exhausted, fyi.

FLATBEDFORD, the isolated systems thing makes sense, especially after looking at the diagram of the distribution block and shuttle... so I will check that the rear adjusters are working or not, per ScreaminZ's advice.

I also suspect that what Wes said about the shuttle being rusted in place may be the case. I think so, because when I had this problem, my brake warning light did not trip. The light is good, so it must be either the switch or circuit, or the shuttle.

If the shuttle has seized in the distribution block, can I do anything about that? I see that the block is no longer available new, so that's not an option. And used might have the same problem. It appears from the diagram that the shuttle might be accessible through the fitting on the end. I could soak it in PB and manually try to move it... but that sounds dicey, and I'd be concerned it would bind again later. Sure would be nice to have the warning system work, though. Does anyone have experience with this?

Thanks!

[fordman]

i guess i didn't explain that very well. i'm sorry i wasn't tryign to say you were ouit of fluid. i was tryign to say what wes was saying. that the fluid wasnt getting to the rear brakes. i am sorry i didn't explain that properly.

[FLATBEDFORD]

I am dealing with a rear brake issue myself. I had super front brakes and no rears. I went through everything. First, I found that the lines out of the master were switched. I fixed that, no help. I pulled the distribution block and replaced it with one that I knew was free (thanks Fordman), no help. I replaced the soft line from the frame to the rear axle, no help. I removed the drums and had them resurfaced and confirmed movement of the rear wheel cylinders, no help. The brakes are bleed and adjusted. Next step is going to be replacing the wheel cylinders, even though they are only about 2 1/2 years old. Don't spend to much time messing with the valve in the distribution block. Mine was moving fine, the switch was broken so I thought it wasn't moving. Check adjusters and wheel cylinders. I am no brake expert, but this is where I got with a similar issue over the last few months.

[robroy]

It's surprising to me that the dual chamber/circuit brake system only has one or two good brake pumps left if one circuit comes open. Sure this is way better than a single circuit that goes out all at once, but it's not too far ahead, especially if the driver fails to notice the change in pedal action before it's too late!

[FLATBEDFORD]

It's surprising to me that the dual chamber/circuit brake system only has one or two good brake pumps left if one circuit comes open. Sure this is way better than a single circuit that goes out all at once, but it's not too far ahead, especially if the driver fails to notice the change in pedal action before it's too late!

With the dual circuit system you don't have only a couple good pumps left. The pedal will drop considerably, but the circuits are isolated. The pedal drops because only one half of the system has pressure, therefore, less pedal resistance. In addition, the failed circuit sucks air in as soon as you let up on the pedal which makes it even lower and softer.

[robroy]

Hey Steve, thanks for clarifying!