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Discussion Starter #1
Ok brothers, at my wits end and need help. My 1991d90 has a brake issue and I can't pass inspection. I have little to no rear brakes. I just rebuilt the entire brake system due to the truck being new to me and the rotors where warped when I bought it.

New:
Rotors
Shoes
Drums
Pads
Master cylinder
Rear brake cylinders, both
Rear brake lines
Cleaned t fitting

The brakes have been bleed many times. Tried gravity, vacuum, and pressure.

Pedal goes down 75% with minimal pressure. Feels like air in system but even under multiple pumps pedal does fully firm up. Front brakes grab nicely and with no issues. When I clamp off rear flex line, pedal stops at 10% of travel and is a solid pedal. I adjusted the drums.

My two thoughts are a blockage in tube or wrong master cylinder.

Please let me know before I punch a baby.

Thanks

Les
 

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Silly question, but you have adjusted the shoes?
 

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Discussion Starter #3
Sure did. Was the first thing that I looked at after bleeding.
 

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A bad brake flex hose can swell under pressure and negate the pressure to the rear brakes.
The brake proportioning valve can also be an issue.
I had a similar issue with our 1983 110 that was caused by the brake springs being installed incorrectly.
It was hard to tell, but I think the springs were pulling the shoe off the adjusting cam.
Anyway, got out the manual and switched the parts around and it worked fine.

Our 1983 is early and I don't know if a previous owner did this, but the rear brake lines had metric threads on one side and SAE fittings on the other side and had rear 109 wheel cylinders.
When I tried to replace the new wheel cylinders I ordered in for a 1983 110, the brake line wouldn't screw in, but luckily we had a set of 109 rear cylinders that worked fine.

Some of the brake petal assemblies have an adjuster that allows you to screw in and out to make the petal rod protrude further in and out against the master cylinder piston.
Screwing it out will cause less play and provide "more petal".
I don't know why, but sometimes air can get trapped in a 110 braking system and you need to adjust the petal.
You then need to adjust the petal out to get sufficient brakes.
As the air purges as a natural result of usage, the petal gets harder until the brakes eventually start dragging.
Then you stop and adjust the rod in to provide free play.
This can sometimes get repeated several times before it doesn't need any more adjustment.
When in this scenario, I keep a length of wood in the car to hold the petal in.
A 17mm wrench to remove the master cylinder, and 2 X 8mm wrenches to screw the end of the rod adjuster and lock it in place.
 

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If a clamped rear brake line gives a firm pedal, then something must not be setup correctly in the drums. are you sure that you have them together properly? Maybe a photo...
 

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Discussion Starter #7
Will get a photo but unless i was missing parts when I bought the truck it is two springs behind the shoes, retainer and the adjuster. Yes, bench bleeding was done prior to install.

I can pull the drum off and had the wife slowly press down the brake (yes I know normally never a good idea) but the brake cylinders are not getting enough fluid to extend fully.

Please keep the ideas coming guys, I have been trying every idea I have.
 

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Will get a photo but unless i was missing parts when I bought the truck it is two springs behind the shoes, retainer and the adjuster. Yes, bench bleeding was done prior to install.
The springs can be in wrong. Did you replace the flex hose?
 

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Discussion Starter #9
Sure did. I am going to feel like an a££ if it is just the springs. Will get a photo out as soon as I get home.
 

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Will get a photo but unless i was missing parts when I bought the truck it is two springs behind the shoes, retainer and the adjuster. Yes, bench bleeding was done prior to install.

I can pull the drum off and had the wife slowly press down the brake (yes I know normally never a good idea) but the brake cylinders are not getting enough fluid to extend fully.

Please keep the ideas coming guys, I have been trying every idea I have.
The rear wheel cylinder pistons should only need to extend a very small amount when all is adjusted properly... like 3 to 6mm depending on shoe adjustment.
Good thing the pistons didn't pop out.

After checking to make sure the rear springs are right, I would move to the petal rod adjustment.
 

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Discussion Starter #11
Red thank you. It was the upper spring position. Now they are perfect better than they have ever been.
 
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