HELP!!!!!!!!!!!!!brake ? for 77 bla

[eugene68]

My friend is working on 77 blazer..4x4
his front brakes were trashed (no grinding though) back brakes look fine after 15 years (yes 15 years)
he has replaced the following on this brake job....

(3) mastercylinders...
front brakes... front calipers, pads, rotors, bearings..
both rear wheel cylinders, shoes...
the problem is this..
He can't get the pedal to pump up.. he got the front brakes working.. but by the looks of it the back brakes haven't worked in 10 years or more..
he replaced the mastercylinder (3rd one on this job) both wheel cylinders, shoes,, made sure they were adjusted.. but cannot get the back brakes to work.. he says it barely dribbles out of the bleeder when he is bleeding them and when he has someone step on it the back will not move at all..

I think it has to be an obstruction in the rear line or the proportioning valve is not working right.. ANYONE out there have any ideas.. something we have missed?????? My friend sounds like he is going to lose his mind and would appreciate any help..

eugene

 

[87 cheverolet]

RE: HELP!!!!!!!!!!!!!brake ? for 77

try changing the proportioning valve and see what happens
after that start replacing lines

87 chevy
305 tbi
2 wd
auto 3 speed

 

[eugene68]

RE: HELP!!!!!!!!!!!!!brake ? for 77

Well I spent the day at my friends house.
I pulled and replaced the proportioning valve with a known working one..
I also sucked out all the back lines with a vacumn pump.. it looked kinda like yellow snot water...

I looked at the proportioning valve the line going to the back brakes was near impossible to get off, and once I got if off, it looked really old rusty clogged....

I had hoped this would fix it it did not.

I then pulled of the vacumn booster, and replaced it with what I think is a good one. but still no back brakes....

anyone have any ideas on what I could be missing?????
( I am so glad this is not my truck!!!!)

eugene

 

[cowboy]

RE: HELP!!!!!!!!!!!!!brake ? for 77

did you replace the brake line going to the rear brakes?
cowboy

 

[MarkyB]

RE: HELP!!!!!!!!!!!!!brake ? for 77

The only solution is to replace the brake lines. Brake fluid will absorb moisture over a period of time. This moisture made its way into the brake lines, hence the rust. This rust has most likely accumulated to a point which is causing the flow restriction. While replacing the line(s), I would pull the wheel cylinders off, pull them apart, and check for any rust which may have migrated inside them during the bleeding process. He may want to check those front lines as well...after 15 years, most likely they are just as bad.

 

[eugene68]

RE: HELP!!!!!!!!!!!!!brake ? for 77

going to help him pull the lines today..
I can't think of anything else it could be.
so far he has put on a new booster, new calipers, new rear wheel cylinders, shoes, pads,proportioning valve, new master cylinder, it's the only thing left it can be...
I will update after the lines are pulled, Think I will pull lines and blow air through, When I bleed the rear brakes with the vacumn pump I heard a pop and the vacumn went down,and all kinds of crap came out,I might have sucked the rust from the prop. valve into rear lines and caused a blockadge. oops..
we shall see...

eugene

 

[eugene68]

RE: HELP!!!!!!!!!!!!!brake ? for 77

Well, I pulled line off the prop. valve going back ..blew air through, then I reassembled all the lines.. Then I hooked a vacumn line to the bleeder with the other end to the vacumn line off my running 68 chevy,,,
primitive but VERY EFFECTIVE!!!!!!!!!! Sucked that crap right out and got to clean my engine at the same time....
we now have brakes!!!!!!!

thanks for the help..
Eugene
( I wouldn't recommend doing it daily though it makes a lot of blue/white smoke)