Need Help with Rear Brakes.

[smpoulin1]

Need some help folks…Can’t seem to get fluid to my rear brakes and my brake light stays on. New proportioning valve (used centering tool to bleed), new master cylinder, blew lines out to ensure no obstructions and still can’t get fluid to the rear. Any ideas? Thanks in advance.

 

[Snoots]

Collapsed rear flexible feed line?

 

[smpoulin1]

Replaced it also….

 

[fast 99]

If the lines are clear verified with air from the master to rear cylinder bleeders either the master is bad or improper bleed procedure.

Could try using a NEW pump oil can filled with brake fluid with a piece of hose attached to a line at master. See if any fluid can be pumped back there.

 

[Turbo4whl]

If the rear brakes shoes are not adjusted out to the drums, then you will have trouble bleeding the rear cylinders. Remember the (self) automatic adjusters will only maintain the adjustment. When the shoes are way out of adjustment, the adjusters will not take up any slack.

One trick, to bleed out of adjusted rear shoes, apply the emergency brake. This moves the shoes to the drums. Then you can bleed them. If the e-brake pedal goes to the floor and the drums still turn, shoes are way out of adjustment.

 

[Grit dog]

You said new master cylinder. Is it fully bench bled?
Could be the problem.

 

[Ricko1966]

Need some help folks…Can’t seem to get fluid to my rear brakes and my brake light stays on. New proportioning valve (used centering tool to bleed), new master cylinder, blew lines out to ensure no obstructions and still can’t get fluid to the rear. Any ideas? Thanks in advance.

Did you get fluid to the rear while you were bleeding the brakes

 

[Dmack]

You didn't say year/model. Some of the later HD trucks had a load sensing valve on the rear axle that can cause problems.

 

[smpoulin1]

If the rear brakes shoes are not adjusted out to the drums, then you will have trouble bleeding the rear cylinders. Remember the (self) automatic adjusters will only maintain the adjustment. When the shoes are way out of adjustment, the adjusters will not take up any slack.

One trick, to bleed out of adjusted rear shoes, apply the emergency brake. This moves the shoes to the drums. Then you can bleed them. If the e-brake pedal goes to the floor and the drums still turn, shoes are way out of adjustment.

Nice tip, will check the adjustment. Thank you.

 

[smpoulin1]

You didn't say year/model. Some of the later HD trucks had a load sensing valve on the rear axle that can cause problems.

85 C10, no valve but thank you.

 

[smpoulin1]

Did you get fluid to the rear while you were bleeding the brakes

Very little, if it sits for a while.

 

[smpoulin1]

You said new master cylinder. Is it fully bench bled?
Could be the problem.

Yes, was fully bled before install.

 

[Ricko1966]

Very little, if it sits for a while.

This makes no sense.Were you getting fluid while you were bleeding the rears?

 

[jtbartsch]

What you will need to do is crack the bleeder screws to the rear drums and perform a gravity bleed on both at the same time or individually. Let it sit overnight and check your clear tubing to see if there is fluid in the line. If so then you need to bleed brakes like normal. I just went through exactly what you are talking about and it was very frustrating to say the least.

 

[Rustisbest]

Pull out the bleeder screws and pump the pedal. Sometimes trash, rust, etc gets stuck in there and they won't bleed. I'd put new screws in while I was there too.