Rear brake bleeding struggles

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Chris64

Full Access Member
Joined
Sep 16, 2024
Posts
80
Reaction score
110
Location
San Diego
First Name
Chris
Truck Year
1974
Truck Model
K20
Engine Size
350
Yours shouldn't have a button. I'd buy a centering tool, unplug the harness from the brake warning light,unscrew the brake warning light. Look at the end of the warning light switch that little Plunger drops into a groove in the shuttle to turn the light off. You should be able to get the shuttle to center by pumping the brake pedal,then opening a front bleeder while holding pressure on the pedal,I've heard of people using a small screwdriver to move the shuttle to center. I've never tried. I believe the threads on the switch are 1/2 x 20 to improvise a centering tool I'd drill the end of a 1/2 x 20 bolt a stick a piece of a nail in the drilled hole. Look on line for a centering tool,a pic and it will make sense.
I think that's a button on the left (it pushes like a button). The plug is in there very tight. At this point I still haven't been able to remove it. This pic makes it look easy to access. The pic lies.

So Am I correct: I need to figure out how to unplug wire, unscrew it and then use a pick or something to recenter it and then use the holder tool to bleed everything?

I'll acquire a holder tool as that sounds like it's required.
You must be registered for see images attach
 
Last edited:

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,610
Reaction score
9,152
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
I think that's a button on the left (it pushes like a button). The plug is in there very tight. At this point I still haven't been able to remove it. This pic makes it look easy to access.

So Am I correct: I need to figure out how to unplug wire, unscrew it and then use a pick or something to recenter it and then use the holder tool to bleed everything?

I'll acquire a holder tool as that sounds like it's required.
You must be registered for see images attach
That's not a button it's a rubber dust cap that seals the valve, don't eff with it,you can't get a new one.And I'd try centering the valve with the pedal first, pump it 3 or 4 times then push and hold while somebody opens right front bleeder. If that doesn't do it,then try centering the shuttle with a small screw driver. Yes you unplug the wire from the switch,unscrew the switch,screw in the centering tool and bleed the brakes.
 
Last edited:

Chris64

Full Access Member
Joined
Sep 16, 2024
Posts
80
Reaction score
110
Location
San Diego
First Name
Chris
Truck Year
1974
Truck Model
K20
Engine Size
350
That's not a button it's a rubber dust cap that seals the valve, don't eff with it,you can't get a new one.And I'd try centering the valve with the pedal first, pump it 3 or 4 times then push and hold while somebody opens right front bleeder. If that doesn't do it,then try centering the shuttle with a small screw driver. Yes you unplug the wire from the switch,unscrew the switch,screw in the centering tool and bleed the brakes.
Here's where I'm lost - If I can get it centered now, can I bleed the rear without the tool?
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,610
Reaction score
9,152
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Here's where I'm lost - If I can get it centered now, can I bleed the rear without the tool?
If you get it centered if no one touches the pedal again, you can vacuum bleed them. If you try to two man bleed them without the centering tool, I don't see you successfully doing it. As for gravity bleeding them IDK,that's a flip of the coin depending on whether you have residual pressure valves either in the master cylinder or combination valve,the standoff valve may prevent it also.
 

Chris64

Full Access Member
Joined
Sep 16, 2024
Posts
80
Reaction score
110
Location
San Diego
First Name
Chris
Truck Year
1974
Truck Model
K20
Engine Size
350
OK, nothing is easy.

I got my holder tool tonight so naturally I had to go out in the dark and give it a whirl.

The switch came out fine but the tool wouldn't fit. A line ran behind it that kept it from lining up with the threads so I had to whittle it down a little.

Before
You must be registered for see images attach

After
You must be registered for see images attach


and now it fit

You must be registered for see images attach


You can see that tube that was blocking it above. I had to take pictures to see any of this.

So while it was off I stuck a test light tip and did some feeling around. It felt centered. I could feel a flat space in the middle and a 45~ degree ramp up to each side. I tried moving it and it didn't want to budge either way.

I was thinking, maybe it only moves under pressure and then moves back (who knows?)

Anyway, so back to vacuuming a rear line. No luck after about 5 minutes.

I guess my next step will be either the line out of this proportional valve or the junction about half way back.

Just thought I would post my latest and document my suffering ;). I'm kidding. This stuff can be fun and I've always dreaded bleeding brakes. When I get this fixed I will be very happy.
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,610
Reaction score
9,152
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
OK, nothing is easy.

I got my holder tool tonight so naturally I had to go out in the dark and give it a whirl.

The switch came out fine but the tool wouldn't fit. A line ran behind it that kept it from lining up with the threads so I had to whittle it down a little.

Before
You must be registered for see images attach

After
You must be registered for see images attach


and now it fit

You must be registered for see images attach


You can see that tube that was blocking it above. I had to take pictures to see any of this.

So while it was off I stuck a test light tip and did some feeling around. It felt centered. I could feel a flat space in the middle and a 45~ degree ramp up to each side. I tried moving it and it didn't want to budge either way.

I was thinking, maybe it only moves under pressure and then moves back (who knows?)

Anyway, so back to vacuuming a rear line. No luck after about 5 minutes.

I guess my next step will be either the line out of this proportional valve or the junction about half way back.

Just thought I would post my latest and document my suffering ;). I'm kidding. This stuff can be fun and I've always dreaded bleeding brakes. When I get this fixed I will be very happy.
Remove the bleeders make sure thay are clear and you can blow through them.Then try 2 man bleeding it now that you have the centering tool in place.
 

Chris64

Full Access Member
Joined
Sep 16, 2024
Posts
80
Reaction score
110
Location
San Diego
First Name
Chris
Truck Year
1974
Truck Model
K20
Engine Size
350
Just to put closure on this, I finally got the new rear hose and surprise - everything is clear and works properly! I may dissect the old hose just to see what the problem was. I'll probably replace the front lines as well.

One of the fittings stripped so that meant I needed to buy a flaring tool. So many new things. but now I have 4 braking wheels.

So based on this, should I be looking at replacing the proportional valve or the master cylinder (etc) or just the two front soft lines? The hard lines all seem fine.
 
Last edited:

Latest posts

Forum statistics

Threads
44,425
Posts
957,600
Members
36,779
Latest member
The Dirty Burb
Top