rear brake proportioning valve and return line

[TRT2]

It appears my 85 4Runner has a return brake line from the rear proportioning valve leading to the front brakes.

Whats up with that? what is the purpose? What happens if you abandon it?

my 82 does not have one...

 

[Poser]

It is a load-sensing proportioning valve, meaning that if you are hauling more weight, the back end of the truck will set down lower, and allow more brake fluid to the rear to help stop, conversly, if you are empty, it limits the fluid flow to the rear in an attempt to not have the rear end lock up on you. I thought that the earlier pickups had a 'pre-set' proportioning valve right by the brake booster/master cylinder..

Hope this helps.

-Steve