braking system split

[Frankenchevy]

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newb alert!

I'm almost positive they do but wanted to confirm, do our trucks have a truly split system for the hydraulics from front to back? I realize they have separate reservoirs, but I wasn't sure if the circuits crossed from the front to the back somehow through the front proportioning valve.

reason I'm asking is I want to remove the rear brake lines to finish up some work, but I need to know if my fronts will still be fully operational to move it in and out of the carport.

thanks!

 

[bucket]

Nope, your brake pedal will go to the floor and fluid will spray from your unhooked line.

This is a common experience for folks in the rust belt, except the line breaks rather than being disconnected.

 

[Frankenchevy]

Nope, your brake pedal will go to the floor and fluid will spray from your unhooked line.

This is a common experience for folks in the rust belt, except the line breaks rather than being disconnected.

crap, I guess I'll have to ease it on out of the carport with a tractor then. you know the thread pitch by any chance? if I could find a cap nut or a nut and bolt to keep it pressurized maybe...

 

[bucket]

It would be best to just not use the brakes.

 

[roundhouse]

Parking brake not work?

Theoretically the dual circuits are for exactly that

If one circuit fails the other would still work

 

[bucket]

Theoretically maybe. But actually, no. You do get a small amount of stopping power, enough to just move the truck around, but it makes a mess and can introduce a bunch of air into the system.

 

[jtridgley79]

crap, I guess I'll have to ease it on out of the carport with a tractor then. you know the thread pitch by any chance? if I could find a cap nut or a nut and bolt to keep it pressurized maybe...

I have plugged mine before. Had a piece of short piece of line left over from another repair and welded the end and stuck it in there. Drove to work for a couple days no problem pedal felt normal.

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[chengny]

crap, I guess I'll have to ease it on out of the carport with a tractor then. you know the thread pitch by any chance? if I could find a cap nut or a nut and bolt to keep it pressurized maybe...

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Too bad you don't want to remove the front lines - that would probably be doable. Read on:

The primary functions of a BPC valve are metering (i.e. by initially limiting the flow of hydraulic fluid to the front circuit until the rear brakes can make frictional contact with the rotating assemblies and rear circuit hydraulic pressure begins to rise).

Once that design pressure in the rear circuit is met, the spool in the BPC valve overcomes spring pressure and shifts -allowing flow to the front brakes. Also at that point, the BPC valve becomes a proportioning valve and it's primary function is to limit flow pressure to the rear circuit. During periods of heavy deceleration, a certain percentage of the vehicle's weight that is normally carried by the rear wheels shifts to the front wheels. The resultant loss of downward force at the rear tires makes them more apt to lose traction with the road surface and skid/fishtail. But, because the proportioning valve is limiting the degree of hydraulic pressure in the rear circuit, the tires can continue to roll on the road.

 

[Frankenchevy]

I have plugged mine before. Had a piece of short piece of line left over from another repair and welded the end and stuck it in there. Drove to work for a couple days no problem pedal felt normal.

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I'm just driving forward 20 feet to get out of the carport to pressure wash and do some sand blasting, then I'm backing it right back into the carport to spray the frame. sounds achievable if you made it all the way to work and back a couple of times.

 

[Frankenchevy]

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Too bad you don't want to remove the front lines - that would probably be doable. Read on:

The primary functions of a BPC valve are metering (i.e. by initially limiting the flow of hydraulic fluid to the front circuit until the rear brakes can make frictional contact with the rotating assemblies and rear circuit hydraulic pressure begins to rise).

Once that design pressure in the rear circuit is met, the spool in the BPC valve overcomes spring pressure and shifts -allowing flow to the front brakes. Also at that point, the BPC valve becomes a proportioning valve and it's primary function is to limit flow pressure to the rear circuit. During periods of heavy deceleration, a certain percentage of the vehicle's weight that is normally carried by the rear wheels shifts to the front wheels. The resultant loss of downward force at the rear tires makes them more apt to lose traction with the road surface and skid/fishtail. But, because the proportioning valve is limiting the degree of hydraulic pressure in the rear circuit, the tires can continue to roll on the road.

this is pretty cool. sounds important enough to replace when I redo all the brake stuff.

 

[Frankenchevy]

Parking brake not work?

Theoretically the dual circuits are for exactly that

If one circuit fails the other would still work

parking brake cables are disconnected too. I removed everything to sand, media blast and paint the back half of the frame.

 

[Frankenchevy]

Theoretically maybe. But actually, no. You do get a small amount of stopping power, enough to just move the truck around, but it makes a mess and can introduce a bunch of air into the system.

I'm replacing and re bleeding the every piece of the braking system before the truck goes back together anyway. I just wanted to move it under its own power as long as possible. I can push and pull it around with a tractor if need be, I was just trying to keep it simple.

 

[bucket]

I'm replacing and re bleeding the every piece of the braking system before the truck goes back together anyway. I just wanted to move it under its own power as long as possible. I can push and pull it around with a tractor if need be, I was just trying to keep it simple.

If you are replacing everything, you just need to attack the line going to the rear that is disconnected. Just fold the line over onto itself and smash it flat with a hammer. You will be fine to move it around then.

 

[Frankenchevy]

If you are replacing everything, you just need to attack the line going to the rear that is disconnected. Just fold the line over onto itself and smash it flat with a hammer. You will be fine to move it around then.

sounds like a plan

 

[bucket]

And since you have the line disconnected already and it's been sitting, don't be alarmed by a squishy pedal feel.