Rear drums not bleeding

[Jstevens7700]

I have a 1983 Chevy C30 dually with a manual transmission and a 6.2 diesel engine. The problem I ran into is the rear drum brakes not having any fluid coming to the cylinders. I even took the cylinders off the lines and mashed the petal and nothing. This truck has sat for nearly 12 years and the wheel cylinder was blown sometime when it still ran. The petal is solid except for a little at the top. I am getting a little fountain of fluid in the small front section of the resivor when pressure is applied to the petal. Tried blowing some air back through the line but still nothing there.

 

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[davester]

I would suggest start moving forward from the rear brakes.  Try disconnecting the rubber lines from the metal line on the frame, and see if you get fluid.

 

If you get fluid there, then the rubber line has probably failed inside.

 

If still no fluid there, find the next connection and disconnect it there.  Repeat as necessary.

[Jstevens7700]

Is there a check valve in the system? Blowing air back through the line should it blow out of the resivor

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[Jsdirt]

Proportioning valve could be jammed shut, favoring the front 100%.

[Jstevens7700]

How would you unjam the proportion valve?

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[Doug_Scott]

First, bleed the master cylinder.  The little spirit you are seeing is the fluid coming through the compensating port, normal.  After bleeding the master try bleeding the combination valve.  You should be able to get fluid out of every line.  Generally combo valves are not serviceable.  They are not designed to go back together.  If you get nothing out of any ports, replace it.  Not something you want to fail when you really need brakes. 

[Jstevens7700]

Just crack the lines and apply pressure to petal to bleed combination valve? Also does the truck need to be running when bleeding? The injection pump is currently at the shop is why I ask.

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[Doug_Scott]

3 hours ago, Jstevens7700 said:

Just crack the lines and apply pressure to petal to bleed combination valve? Also does the truck need to be running when bleeding? The injection pump is currently at the shop is why I ask.

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 It will be tough to pump the pedal without the booster.  And, yes, just pump pedal, hold down, and crack open bleeder.

There is something you can try to help free up the combo valve, when you open the bleeder on the front pedal, push the pedal as far as you can.  Sometimes the proportioning valve part will free up with the other side (front) open.  It will also set the brake warning light if the pressures are far enough different.

[davester]

If a port is open so fluid comes out, I've found that pushing the pedal down is pretty easy, even with the engine off.  And I've done multiple vehicles like this, before I got my pressure bleeder for my truck.