Unkown fitting on rear brake line

[tvjthomas]

I was investigating a loss of brakes and found this unkown fitting attached to the brake line feeding the rear brakes. No diagram I could find it showed it and no one I knew with one of these trucks have seen it either. The lower line is being fed from the proportioning valve and the top line feeds the rear brakes, the fitting in question is located before the rear diff and is attached to the frame and rear diff where the brake lines split. Any help would be much appreciated before I just keep throughing money at the problem.

 

[bucket]

It's a load compensating valve. When the truck is loaded down, it applies more pressure to the rear brakes.

 

[tvjthomas]

Interesting, would that also be able to cut brakes to the rear? Also thank you very much, it's always a good day when you learn something new.

 

[xm20k]

A lot of people take it out, it's mechanical can be worn and not work by just bypassing fluid, it has seals that can go bad and can leak, or trap junk and plug up. I don't think it's designed to restrict flow enough to make the rears not work, but if it's full of junk it could.

 

[tvjthomas]

A lot of people take it out, it's mechanical can be worn and not work by just bypassing fluid, it has seals that can go bad and can leak, or trap junk and plug up. I don't think it's designed to restrict flow enough to make the rears not work, but if it's full of junk it could.

Would you have any advice on removing it? My first though would just be to gently bed the line and connect them with a union.

 

[xm20k]

Would you have any advice on removing it? My first though would just be to gently bed the line and connect them with a union.

You could try that as long as the lines aren't brittle.

 

[Chevy 88]

Coupler.

 

[tvjthomas]

You could try that as long as the lines aren't brittle.

I haven't seen any signs or deterioration on them and I sounds like it would be a little cheaper and easier than running a new line, then hopefully I would finally have reliable brakes again.

 

[tvjthomas]

Coupler.

Thank you, do you know what size that would be?

 

[bucket]

What are the brake issues? Personally, I'd much rather diagnose the problem instead of messing with things that may not be the issue.

 

[xm20k]

Thank you, do you know what size that would be?

3/8 inverted flair if I remember correctly.

If the rears are just not working, and no leaks anywhere it could be plugged It's worth a try before you get into replacing stuff as it's really not a needed item.

 

[bucket]

Coupler.

Yep. That sure is a coupler.

 

[tvjthomas]

What are the brake issues? Personally, I'd much rather diagnose the problem instead of messing with things that may not be the issue.

It's only an issue when driving and pumping the brakes a couple times in park causes them to work again. Sometimes they don't work at all and sometime it's while you are breaking, also the front will still stop me but only with the petal all the way down. There is also no leaks, I just replace the rear wheel cyclinders as one of them was leaking. I have also bled them and re check for any air and replaced the brake booster. I might get a new proportioning valve to see if that fixes it too. I have only had this truck since December so I'm still figuring all this out and deeply appreciate all your help, truly thank you.

 

[Chevy 88]

You could try soaking all that stuff in water or WD40 to see if the moving parts free up and start working properly. Something might be binding.

 

[legopnuematic]

Are the shoes in the rear adjusted properly?