Problems brake bleeding

[afcamaro]

I have a '70 with disc brakes up front and I am having trouble with bleeding the brakes. The rear drums will bleed fine, but it will hardly even trickle out of the front bleeders.
Do I have to push that button in on the proportioning valve? And what do I use to do that, c-clamp?

Any other suggestions?

[Longhorn 70]

I had a similar problem when I still had drums. After changing the master I had to really push down on the pedal hard and hold it down. Then push harder until a pop was heard. Then I was able to bleed well....

Another thing I tried was to use a bottle with a tight fitting hose in the top that ran to the bottom of the bottle and attach that to the bleeder screw. I then took a vacuum pump and hooked it up to another hose in the top of the bottle. I ran the pump at about 2" of vacuum until the reservoir was ALMOST empty. Fill and repeat. I went through a quart of fluid for both sides but it cleaned the air and junk out.

[cdowns]

yes the proper way to bleed brakes according to the GM service manual is to clamp the pin on the valve/// there is a specialty tool to do it but i have used a c clamp to do the job

[slow-1]

Near the end of this thread there are pics and descriptions of how I did it...I never could get it to "pop" on its own.

http://67-72chevytrucks.com/vboard/s....php?p=6174272

[68gmsee]

Don't forget that the front rubber lines will swell almost shut from the inside making it hard to bleed. It also will cause the brakes to lock by preventing fluid to return to the m.c.

If you have trouble locating where the restriction is loosen the connection to the front brakes at the m.c. and have someone depress the pedal (make sure fluid doesn't drip on painted surfaces). Continue by loosening other connections and doing the same test.

[Stocker]

Originally Posted by slow-1

Near the end of this thread there are pics and descriptions of how I did it...I never could get it to "pop" on its own.

http://67-72chevytrucks.com/vboard/s....php?p=6174272

Those pictures are truly worth a thousands words!!

[RichardJ]

That other thread is interesting and very similar to this one in that there are a bunch of very confused people.

1st, drum/drum brakes DO NOT have proportioning valves, combination valves or shudder, port valves. They simply don't.

Drum/drum brakes have a F/R pressure differential warning switch mounted inside a distribution block. It has one job and one job only. It turns a dash brake light ON if there is a brake failure. A difference in front to rear pressure will move the piston.



This is a stand alone, non-adustable, proportioning valve used on some GM and Mopar vehicles in the late 60's. I have seen them on 1st Gen Camaro's and my '69 RoadRunner has the same one.


They both mounted them in the rear brake line, back near the axle. Car manufacturers, and the aftermarket have a tendancy to not be consistant with terminology. As you can see here, they called the proportion valve a "regulator valve". It is in a sense, but the regulation is variable.


This is an aftermarket, stand alone, adjustable proportioning valve.


This is a Camaro, stand alone, metering valve. The pin used for bleeding the front brakes is on the rear of it. This valve is sometimes called a hold-off valve. It prevents fluid from flowing and pressure building on the front brakes until pressure reaches about 40 psi. This keeps the front brakes from working until the rear brakes are ready. It may even start dragging the rear brakes ahead of the front brakes. Its primary function is to prevent the car from nose-diving on light brake application.


This is an aftermarket, stand alone, metering valve. The pin is under that rubber cover.



Some metering valves require that the pin be pulled out when bleeding. This one happens to be from a fnord.



This is a Combination valve. It contains three separate valves and they function independently of each other. The pin on the metering valve is not connected to, nor does it play any part in the function of the pressure differential switch.


This is a variation of the combination valve pictured above. It functions the same. The vertical lines show the three distinct areas in the unit.

[slow-1]

Originally Posted by Stocker

Those pictures are truly worth a thousands words!!

Thanks...hope they help someone work through their brake situation.

[slow-1]

Originally Posted by RichardJ

That other thread is interesting and very similar to this one in that there are a bunch of very confused people.

1st, drum/drum brakes DO NOT have proportioning valves, combination valves or shudder, port valves. They simply don't.

Drum/drum brakes have a F/R pressure differential warning switch mounted inside a distribution block. It has one job and one job only. It turns a dash brake light ON if there is a brake failure. A difference in front to rear pressure will move the piston.



This is a stand alone, non-adustable, proportioning valve used on some GM and Mopar vehicles in the late 60's. I have seen them on 1st Gen Camaro's and my '69 RoadRunner has the same one.


They both mounted them in the rear brake line, back near the axle. Car manufacturers, and the aftermarket have a tendancy to not be consistant with terminology. As you can see here, they called the proportion valve a "regulator valve". It is in a sense, but the regulation is variable.


This is an aftermarket, stand alone, adjustable proportioning valve.


This is a Camaro, stand alone, metering valve. The pin used for bleeding the front brakes is on the rear of it. This valve is sometimes called a hold-off valve. It prevents fluid from flowing and pressure building on the front brakes until pressure reaches about 40 psi. This keeps the front brakes from working until the rear brakes are ready. It may even start dragging the rear brakes ahead of the front brakes. Its primary function is to prevent the car from nose-diving on light brake application.


This is an aftermarket, stand alone, metering valve. The pin is under that rubber cover.



Some metering valves require that the pin be pulled out when bleeding. This one happens to be from a fnord.



This is a Combination valve. It contains three separate valves and they function independently of each other. The pin on the metering valve is not connected to, nor does it play any part in the function of the pressure differential switch.


This is a variation of the combination valve pictured above. It functions the same. The vertical lines show the three distinct areas in the unit.

That's some good info...thanks for sharing.