Advice Needed on Troubleshooting Brakes, Please!

[Zeus51]

Hey guys, about two months ago I noticed my proportioning valve leaking as well a few other brake line leaks which lead me to figure out that someone had mixed two different brake fluids in the master cylinder. So I started on an adventure to install a new brake system from master cylinder all the way to new bleeder valves. But I'm having an issue that I am sure you guys can help me with.

I purchased all products from Summit Racing that were suppose to be compatible with a 1984 Chevy K30. The master cylinder and proportioning valve are "Right Stuff Detailing G0571" which includes both in one kit. The brake lines are 'Classic Tube Stainless Steel' prebent lines with stainless steel braided hoses and Russell Solo Bleeders.

I have installed everything but I still have maybe 10% brakes. I can't seem to establish pressure to bleed the rear brakes. All four brakes will gravity bleed without issue and the front brakes WILL pressure bleed. I am using the proportioning valve tool to prevent the valve from sensing a depressurization and therefore tripping the inner mechanism inside the proportioning valve. I am also doing all of the bleeding attempts with the vehicle running as per the manual. It is worth mentioning that I am on my second proportioning valve bc I would've sworn that the valve was bad. Also, I have checked for leaks at least 10 times with the brake pedal depressed and have not found any as of yet.

Could it be that this master cylinder is incompatible? Has anyone used this particular master cylinder and had successes or failures? I will attach a link for the cylinder for readers reference. Please help! I am running out of ideas.


https://www.summitracing.com/parts/RSD-G0571

 

[porkysplace]

Hey guys, about two months ago I noticed my proportioning valve leaking as well a few other brake line leaks which lead me to figure out that someone had mixed two different brake fluids in the master cylinder. So I started on an adventure to install a new brake system from master cylinder all the way to new bleeder valves. But I'm having an issue that I am sure you guys can help me with.

I purchased all products from Summit Racing that were suppose to be compatible with a 1984 Chevy K30. The master cylinder and proportioning valve are "Right Stuff Detailing G0571" which includes both in one kit. The brake lines are 'Classic Tube Stainless Steel' prebent lines with stainless steel braided hoses and Russell Solo Bleeders.

I have installed everything but I still have maybe 10% brakes. I can't seem to establish pressure to bleed the rear brakes. All four brakes will gravity bleed without issue and the front brakes WILL pressure bleed. I am using the proportioning valve tool to prevent the valve from sensing a depressurization and therefore tripping the inner mechanism inside the proportioning valve. I am also doing all of the bleeding attempts with the vehicle running as per the manual. It is worth mentioning that I am on my second proportioning valve bc I would've sworn that the valve was bad. Also, I have checked for leaks at least 10 times with the brake pedal depressed and have not found any as of yet.

Could it be that this master cylinder is incompatible? Has anyone used this particular master cylinder and had successes or failures? I will attach a link for the cylinder for readers reference. Please help! I am running out of ideas.


https://www.summitracing.com/parts/RSD-G0571

Did you bench bleed the master cylinder ?

 

[sandcobra164]

How is your power steering pump? Turn the steering wheel and see. Unlike a gasser powered truck, these have a hydraulic powered brake booster which gets it's assist from the power steering system instead of vacuum. I know when I was going through fueling issues which would cause mine to stall when slowing to make a turn, it would go to a stiff pedal without much braking action in a flash. There is supposed to be an accumulator to prevent that but maybe mine is stuck? Brakes work fine when the engine is running.

 

[FrankenCub]

I've also had an instance where a proportioning valve on my last truck was air locked resulting in the same problem. Once I bled it out I had no problems doing the rest of the system.

 

[Drock]

Not sure what the bore is on the stock master?, but 1" sounds awful big! Also some master cylinders have a different stroke. I would suggest replacing the master with a stock replacement.

 

[Zeus51]

Yes. I bench bleed the master. Everything appeared to be normal at that time. My power steering pump is good. Turning the wheels feels normal. I guess I will look at autozone for a different master cylinder. Does that seem to be the consensus?

Frankencub, how'd you de-air the prop Valve? Just crack open one of the front brake lines?

 

[Zeus51]

Gentlemen, thank you for your help. I picked up a new master cylinder at O'Reilly's today. I bought the Model #: NMC1982 for $44. It fixed the issue. It was a win win since the new MC was cheaper than the one I bought from summit. Mailing the other back tomorrow. It feels good to be able to drive the truck again.

 

[Recovry4x4]

Good news.

 

[FrankenCub]

Yes. I bench bleed the master. Everything appeared to be normal at that time. My power steering pump is good. Turning the wheels feels normal. I guess I will look at autozone for a different master cylinder. Does that seem to be the consensus?

Frankencub, how'd you de-air the prop Valve? Just crack open one of the front brake lines?

I see you have your problem solved, good deal
If you ever do run into the air in proportioning valve issue, I cracked the lines one at a time and bled them the same as a bleeder valve on a wheel cylinder with a helper at the peddle.