What is this brake line?

[Ricky8227]

I’m previous owner swapped a 8.8 in. And I notice this brake line is cut and slowly dripping.. brakes work but where was this line suppose to go? And how should I fix it? 

[Pete M]

did they swap in a regular prop valve up front?

[Eagle_SX4]

One of those lines is the emergency bypass line for the rear brakes. Originally there was a weight biased proportioning valve bolted under the bed. With a rod down to the axle to adjust the rear brakes based on weight in the bed.

 

There are several ways to remove and bypass the valve. Some put a plug in the distribution block for the emergency bypass line. (easiest option). Others like me have replaced the distribution block with an adjustable proportioning block. (requires new hard brake lines front to back)

[Ricky8227]

1 hour ago, Eagle_SX4 said:

One of those lines is the emergency bypass line for the rear brakes. Originally there was a weight biased proportioning valve bolted under the bed. With a rod down to the axle to adjust the rear brakes based on weight in the bed.

 

There are several ways to remove and bypass the valve. Some put a plug in the distribution block for the emergency bypass line. (easiest option). Others like me have replaced the distribution block with an adjustable proportioning block. (requires new hard brake lines front to back)

Where exactly do I put the plug? Are you talking about the block on the rear axle? Or is there somewhere else you’re talking about? The block on my axle has 3 lines going to it. Left and right brakes and the main brake line in the center. How do I block off the line that is cut? 

[Ricky8227]

1 hour ago, Pete M said:

did they swap in a regular prop valve up front?

I am not sure I will have to look. Not very familiar with there that even is. I Just want to be able to plug that line that is cut and dripping 

[Eagle_SX4]

14 minutes ago, Ricky8227 said:

Where exactly do I put the plug? Are you talking about the block on the rear axle? Or is there somewhere else you’re talking about? The block on my axle has 3 lines going to it. Left and right brakes and the main brake line in the center. How do I block off the line that is cut? 

This explains it better than I could.

 

 

[Pete M]

snap us a couple pics of the part under the hood that looks like a proportioning valve.   if you still have the original combo valve, then you'll need to plug the bypass line output.  if you have an XJ prop valve swapped in, then there's nothing to plug and that line that's dripping likely leads no where and it's just dripping the fluid that's trapped inside. 

 

how well does the truck stop if you step hard on the brakes?

[Ricky8227]

14 hours ago, Pete M said:

snap us a couple pics of the part under the hood that looks like a proportioning valve.   if you still have the original combo valve, then you'll need to plug the bypass line output.  if you have an XJ prop valve swapped in, then there's nothing to plug and that line that's dripping likely leads no where and it's just dripping the fluid that's trapped inside. 

 

how well does the truck stop if you step hard on the brakes?

 

[Ricky8227]

Just now, Ricky8227 said:

 

Sorry don’t why it posted the second pic upside down 

[Eagle_SX4]

It looks like both rear brake lines are still hooked up to the distribution block so you will need to delete the emergency bypass line. It is most likely the one that was cut and is leaking. However with that being said whoever swapped the axle in didn't do a great job by only cutting the line. I would trace your brake line all the way to the back and make sure the proper one is hooked up to the forward most port on the distribution block.

 

Also it looks like your leaf spring is bent in this photo. Near the front eyelet.

On 2/25/2026 at 7:08 PM, Ricky8227 said:

 

 

[AZJeff]

As someone who has deleted the load valve assembly, I will make an important comment about the current state of the brake tubing in the OP’s first photo:

 

There is a LONG section of tubing that hangs out, unsupported, from where it is clipped to the “frame” rail until it joins the flexible hose the goes down to the axle housing.   
 

Leaving this tubing to flop around unsupported is inviting a fatigue failure cracking off the tube at some point.  Ideally, some sort of bracket should be employed to attach the tube to the chassis right at the junction Of the flex hose and the tube.  This is way the factory did it.

[Ricky8227]

10 hours ago, Eagle_SX4 said:

It looks like both rear brake lines are still hooked up to the distribution block so you will need to delete the emergency bypass line. It is most likely the one that was cut and is leaking. However with that being said whoever swapped the axle in didn't do a great job by only cutting the line. I would trace your brake line all the way to the back and make sure the proper one is hooked up to the forward most port on the distribution block.

 

Also it looks like your leaf spring is bent in this photo. Near the front eyelet.

 

So the main brake line in the back should be hooked up to this part that circled? 

[Eagle_SX4]

Yes, and the port on the front port on the bottom needs to get plugged.

[Ricky8227]

2 minutes ago, Eagle_SX4 said:

Yes, and the port on the front port on the bottom needs to get plugged.

Thanks for your help man. What’s the best way of plugging it? 

[Pete M]

should be a writeup on that in the link in my signature. 

 

if your rear tires are locking up first, you may need to add an inline prop valve to the rear line.

[Eagle_SX4]

7 hours ago, Ricky8227 said:

Thanks for your help man. What’s the best way of plugging it? 

The thread I linked earlier has the info for blocking off the port.