proportioning valve button

[escobar]

I've read on this forum about keeping the prop. valve button depressed while bleeding. What's the purpose of this? Does it deactivate the pressure regulation to bleed more thoroughly?

Thanks

 

[jeffgtoman]

In the early days before ABS, the proportion valve was needed when you have disc front and drum rear brakes because you needed 50 psi to overcome the spring pressure on the rear shoes. So if you are trying to bleed brake lines that are full of air, the proportion valve could stay shut, causing problems getting all of the air out. Now it is used even more. It never went away and I'm not sure of all of it's current duties. The older ones had to be pulled out. I have a tool that holds it out. There is also a tool to hold them in. Maybe someone else knows exactly which one applies to your Jeep.

 

[escobar]

Well its also to ensure a greater front end application for steering and stopping.

That little button though. Never heard of such a thing.

 

[dalefan88]

In the early days before ABS, the proportion valve was needed when you have disc front and drum rear brakes because you needed 50 psi to overcome the spring pressure on the rear shoes. So if you are trying to bleed brake lines that are full of air, the proportion valve could stay shut, causing problems getting all of the air out. Now it is used even more. It never went away and I'm not sure of all of it's current duties. The older ones had to be pulled out. I have a tool that holds it out. There is also a tool to hold them in. Maybe someone else knows exactly which one applies to your Jeep.

View attachment 4571

View attachment 4572

i had to use the one on the bottom. had to take a dremal and widein it out to make it fit.