Rear Brake Bleeding Issue

skrelnik

TJ Addict
Lifetime Supporting Member
Joined
Jan 10, 2018
Messages
2,874
Location
CT, United States
Hi Guys - tackled a brake job today, pads and rotors, as well as the e-brake shoes. I had a major rear brake issue where a caliper was sticking and my existing rear passenger pad was toast, like no more pad remaining - my rear wheels were on fire (figuratively). I attempted to bleed the brakes the old school way, depress the brake pedal and hold. I clearly introduced air into the brake system which, I think, led to my new issue, which is a mushy brake pedal - and I must slam the brake pedal to come to a stop - Only testing in my driveway, not on a public road.

I picked up a pressure bleeder to bleed the brakes, and I ran into an issue with the rear calipers. The fronts flow perfectly but the rear calipers are dripping out like a drip a minute. My forum research tells me that the shutter valve (combination block) may be stuck, but I cannot find how to rectify this situation? Is there a fix to this? Or do I need to remove the Master Cyl and bench bleed that, and also remove the combination block to inspect?

Thanks in advance!
 
Here's some instructions posted by @mrblaine in another thread. If the brake light comes on, that means the shuttle valve is getting stuck.

"Do not do the pump and hold. Simply open bleed screw, push pedal down hard and fast, hold at bottom, close bleed screw, let pedal up. This time do it with the parking brake off and the key on. Watch the brake light on the dash, if it comes on, close bleed screw, pump pedal until it goes off, resume bleeding. What is likely happening is the shuttle valve is being shifted and closing off the circuit with the leak."
 
Did you remove/replace the rear calipers? If you put them on upside down (and thus on the wrong side) they will be mushy no matter how many times you try to bleed them
 
  • Like
Reactions: skrelnik
Here's some instructions posted by @mrblaine in another thread. If the brake light comes on, that means the shuttle valve is getting stuck.

"Do not do the pump and hold. Simply open bleed screw, push pedal down hard and fast, hold at bottom, close bleed screw, let pedal up. This time do it with the parking brake off and the key on. Watch the brake light on the dash, if it comes on, close bleed screw, pump pedal until it goes off, resume bleeding. What is likely happening is the shuttle valve is being shifted and closing off the circuit with the leak."

Thanks for that LJGreg - and I did read that, and yes, the brake light did come on at first, and that's what led me to this post by Blaine. Now the brake light is no longer present.

Also, the pedal is no longer mushy - Jeep is running in the driveway, so I intend to brin it back inside and see if I can bleed the rears...
 
Did you remove/replace the rear calipers? If you put them on upside down (and thus on the wrong side) they will be mushy no matter how many times you try to bleed them

Thanks for the reply, but the calipers are good - and pedal is no longer mushy. Yay! Hopefully the rear calipers will bleed when I get back out there...if not :unsure:
 
Here's some instructions posted by @mrblaine in another thread. If the brake light comes on, that means the shuttle valve is getting stuck.

"Do not do the pump and hold. Simply open bleed screw, push pedal down hard and fast, hold at bottom, close bleed screw, let pedal up. This time do it with the parking brake off and the key on. Watch the brake light on the dash, if it comes on, close bleed screw, pump pedal until it goes off, resume bleeding. What is likely happening is the shuttle valve is being shifted and closing off the circuit with the leak."

Test drove the car, brakes work fine - no mushy pedal, but there is no brake fluid flow from the rear calipers, so there is some issue there. My pressure bleeder is holding 16 PSI without any leaks. Do you see anything wrong here? The brake light is not on, unless I pull the e-brake, so that is working as it should be.

1650134486523.png


1650134478898.png
 
@mrblaine - I do not generally like asking you direct questions, but can you identify anything I should be testing or looking for? Recap:

1) Changed rotors/pads/calipers and ebrake shoes.
2) Bled breaks (old school way) and possibly got air into the brake system as I had (1) a very mushy pedal and (2) droplets of fluid flowing from the rear calipers. Front calipers flow very well.
3) Bled breaks using the pressure bleeder, and now I have a hard pedal, but still only droplets of fluid flowing from the rear calipers, and front calipers flowing very well. Pressure Bleed holds 16psi.

Post 6 shows the caliper's open valve and nothing coming out, and the pressure bleeder holding that 16psi.
 
@mrblaine - I do not generally like asking you direct questions, but can you identify anything I should be testing or looking for? Recap:

1) Changed rotors/pads/calipers and ebrake shoes.
2) Bled breaks (old school way) and possibly got air into the brake system as I had (1) a very mushy pedal and (2) droplets of fluid flowing from the rear calipers. Front calipers flow very well.
3) Bled breaks using the pressure bleeder, and now I have a hard pedal, but still only droplets of fluid flowing from the rear calipers, and front calipers flowing very well. Pressure Bleed holds 16psi.

Post 6 shows the caliper's open valve and nothing coming out, and the pressure bleeder holding that 16psi.
I would start with the stock rubber flex hose if it still exists and still has the clamp on it that holds it to the upper control arm. If you live where it rusts, that clamp will rust around the hose and squeeze it shut. That will explain both your old problem of the parts on fire because they couldn't release and the new problem where no fluid comes out. Start there.

I don't know what old school is. Explain that.

FYI- you don't have to ask directly, you can however, tag me and if I have something of value to add, I will. If not, then I'll just fuck with you.
 
I would start with the stock rubber flex hose if it still exists and still has the clamp on it that holds it to the upper control arm. If you live where it rusts, that clamp will rust around the hose and squeeze it shut. That will explain both your old problem of the parts on fire because they couldn't release and the new problem where no fluid comes out. Start there.

I don't know what old school is. Explain that.

FYI- you don't have to ask directly, you can however, tag me and if I have something of value to add, I will. If not, then I'll just fuck with you.

Thank you for this, and I do live in rust country so yeah, that could be the issue.

Old school, to me, is just depressing and holding the brake pedal to get the fluid out...since we now have these pressure bleeders that the average Joe can afford.
 
Thank you for this, and I do live in rust country so yeah, that could be the issue.

Old school, to me, is just depressing and holding the brake pedal to get the fluid out...since we now have these pressure bleeders that the average Joe can afford.
Open bleeder, push pedal fast to floor and hold. Close bleeder, let pedal up. Repeat 3-7 times per corner. If that doesn't get the system bled, you have a problem, find it.

All modern masters aerate the fluid with 100's of tiny bubbles after a few pumps. It is always a good idea to do a 1-2 pedal bleed at each corner the next day.
 
  • Like
Reactions: skrelnik
Open bleeder, push pedal fast to floor and hold. Close bleeder, let pedal up. Repeat 3-7 times per corner. If that doesn't get the system bled, you have a problem, find it.

All modern masters aerate the fluid with 100's of tiny bubbles after a few pumps. It is always a good idea to do a 1-2 pedal bleed at each corner the next day.

I think it was that rubber flex hose....I just grabbed it and pretended I was a 13-year old boy who just discovered masterbation. I got some flow from the rear passenger caliper!!! I actually have a replacement part for that hose, so I guess I should change that part and see how it goes. Thank you!!!
 
Open bleeder, push pedal fast to floor and hold. Close bleeder, let pedal up. Repeat 3-7 times per corner. If that doesn't get the system bled, you have a problem, find it.

All modern masters aerate the fluid with 100's of tiny bubbles after a few pumps. It is always a good idea to do a 1-2 pedal bleed at each corner the next day.

Both rear calipers are flowing like a champ!!! Many thanks to the brake master!
 
All modern masters aerate the fluid with 100's of tiny bubbles after a few pumps. It is always a good idea to do a 1-2 pedal bleed at each corner the next day.
@mrblaine what is different on modern MC vs. Vintage MC. I believe you Blaine, just curious what's different ?
 
@mrblaine what is different on modern MC vs. Vintage MC. I believe you Blaine, just curious what's different ?
No idea. I just know they do it. Not hard to see. Just do a good bleed and watch the fluid in a clear hose. 5-7 pumps in, you'll see 100's of tiny little bubbles distributed throughout the fluid.
 
No idea. I just know they do it. Not hard to see. Just do a good bleed and watch the fluid in a clear hose. 5-7 pumps in, you'll see 100's of tiny little bubbles distributed throughout the fluid.
Weird , Good to know though Thanks Blaine.