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Odd braking issue...

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KeyBlazer

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Location
Irvine, California
My 73 Blazer has been sitting for a while, cos I have been busy, and also cos I cant get it to stop!..
It does brake, but slowly, and if I really push hard(Both feet), the pass rear wheel will just lock.
Front won't lock.
The PO told me he changed front and rear pads, front and rear flexible lines, and rear cylinders.
I adjusted the rear shoes, then rebled the brakes, .
No change.
Then I replaced the Master Cylinder and booster with one from a 1990 3/4 Suburban, and rebled.
No change, so its been sitting for a month.
Friday, I did some driving around a parking lot, hitting the brakes hard and hoped something would clue me up.
After I did this I felt the brake surfaces.. Both front rotors were hot, and the Pass rear drum was hot, but drivers rear was stone cold.
Maybe I am being stupid, but if the fronts are getting hot then the brakes must be working... and if the Drivers rear was bad somehow, I would expect good brakes on 3 wheels..
Ideas?
 
Sounds like the proportioning valve is out of wack and giving too much pressure to the rear wheels. That doesn't explain why the driver's side rear isn't braking though...
 
Proportioning valve?
Maybe thats it... How do I test that?
Clearly I gotta pull that drivers rear and see what is going on, but it does not explain the lack of braking elsewhere.
The pedal feels normal, and the booster is working, ie, you can pump it out to a hard pedal when engine is stopped and when starting the pedal sinks.
 
well here's an article from chevy hi performance, some good information even if it is mostly about installing an adjustable valve. http://www.chevyhiperformance.com/techarticles/71398_install_brake_proportioning_valve/index.html

And a more detailed, yet general article from StopTech:
http://www.stoptech.com/tech_info/wp_proportioning_valves.shtml

Usually anytime the rear wheels lock up before the fronts do, your proportioning valve is not doing it's job. Testing it is basically what you did in the parking lot, some 30-0 and 60-0 braking tests will tell you whether or not the valve is working correctly.
 
KeyBlazer said:
My 73 Blazer has been sitting for a while, cos I have been busy, and also cos I cant get it to stop!..
It does brake, but slowly, and if I really push hard(Both feet), the pass rear wheel will just lock.
Front won't lock.
The PO told me he changed front and rear pads, front and rear flexible lines, and rear cylinders.
I adjusted the rear shoes, then rebled the brakes, .
No change.
Then I replaced the Master Cylinder and booster with one from a 1990 3/4 Suburban, and rebled.
No change, so its been sitting for a month.
Friday, I did some driving around a parking lot, hitting the brakes hard and hoped something would clue me up.
After I did this I felt the brake surfaces.. Both front rotors were hot, and the Pass rear drum was hot, but drivers rear was stone cold.
Maybe I am being stupid, but if the fronts are getting hot then the brakes must be working... and if the Drivers rear was bad somehow, I would expect good brakes on 3 wheels..
Ideas?
Click to expand...

So you have one side in the back that is not working, which puts more power to the other side so it locks up.
Your issue is most likely in the tube going to that tire.
You could check at the distribution block bolted on the pumpkin in the back.
If you changed the rear cylinders, maybe one was bad or is installed wrong, or the tube going to the cylinder is plugged.
 
Check to be sure the PO didn't halfass the brake job and that he actually put pads in the driver's rear drum.
 
Pull the drums off and check to see if the drivers side was assembled correctly. While you have it in the air. Have someone press on the brakes with the trans in neutral and see if there is any resistance to you turning the wheel. When you rebled the system, was there allot of fluid flowing out of the drivers side wheel cylinder? Or did it just kinda drip out?
 
In fact I already had both side off a few months ago and noticed nothing odd. When I bled them(Twice) I thought everything bled normally, with no disproportionate fluid flow.
I got under it today and looked over the lines, and no sign of damage.
Clearly there is something wrong with the drivers rear, but I would expect to get better braking with some yaw to the right, not crap braking with a slight bias...
 
I thought that too, but if they were I would not be getting even heat from them after a couple of stops... would i?
 
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