IngSoc

So got my truck running and the breaks are giving me issues. Ok so here it goes. I bled the breaks very well for any air. The master is new and out of my old cab ( less than 5k miles on it) I swaped the cab for a nicer newr looking cab and left the booster on it. MY friend is convinced its the boooster. Here is the symptoms. When the truck is off I get pressure on the breaks, when I turn it on I loose all pressure. Idle changes a little bit when the vacume line is in the booser and I pump what little movement I get. I plug the vacume line off the EFI and I get verry little breaks (last 1/4 inch of the pedal) Im not sure whats going on. I put in a Manuel LPV and tinkering with that... I had to remove the return line off the rear breaks to the master and got that pluged off well. IDK any suggestions would help me justify a $250 booster. Thank guys.

IngSoc

Another thing to add is that the new cab is from a 3.0 and mines a 2.4. Not sure if there compatable.

abecedarian

Return line from the rear what? There is no return line from the rear LSPV.

IngSoc

Off the master there are 2 lines. The one goes to a bracket mounted on the lower 2 bolts on the master. That T`s off into 2 lines. 1 line heads twords the driver front calliper. The other side of the T goes off to the passenger side frame rail. That 2 spl;its the line into 2, one line going into the front passenger side calliper. The other line off the T goes to the LPV in the rear. Top line goes into the LPV, 1 line to the rear breaks and another line to the front "L?" fitting. That line goes up and back around to the master. I completely bypassed the 2end line that does NOT go to the t fitting with the front break... Not sure if that made it any more clear or foggy but thanks for the late night responce.

abecedarian

I get what you're saying. But there is no "return" line from the rear proportioning valve- technically known as a "Load Sensing Proportioning, Bypass Valve", or LSP-BV.

It gets pressure directly from one side of the master cylinder, the "rear circuit" and gets pressure from a tee by the right-front wheel, which is given pressure from the other side of the master cylinder, the "front circuit".

The purpose of the rear proportioning valve is to sense the rear height... the load in the rear- which is the arm that reaches across and connects to the rear axle and it varies the rear brake pressure accordingly. It has a connection to the front brakes, which many people errantly call a return line, that senses the front brake pressure. If the front brake pressure is too weak, i.e. because of a major malfunction in the front brakes, the valve in the rear will then allow full brake pressure to be applied to the rear brakes regardless of the load in the back.

Maybe this will help you make sense of your brake problem.

ahickman

Did you adjust the push rod to the correct depth before putting the master cylinder on the booster? I struggled with a very similar issue on an 86 I got for my brother-in-law and after many hours of troubleshooting, found that a few turns off the rod to increase the length took care of the issue.

IngSoc

Thanks abe. Knew that the "return line" did something of the sorts of helping witht he fronts, just never knew exactly how. Im personaly thinking its any thing exept the $250 part tahts bad.... Thus leading me to belive its the push rod =) I guess I will try some reserch to figure out how to adjust this. Thanks for the information so far guys. Be great if I could take her out for the first time in 8 months! ... Test out these 35`s

IngSoc

So the breaks and the idle are doing diffrent and its about to make me go throw my self off the top of my truck. Unpluged the vacume line stuck a bolt in it to take it out of the garage so I could work on it out side... as I was driving around my parking lot I could hear a major vacume leak... Where IDK not sure if it was while I was turning, breaking .... turning and breaking, IDK. What happend after that made me want to cry. So im turing it around to put it in the work zone and all of a suddin my idle drops a fat one and truck starts paceing and misfireing and has black smoke coming out the tailpipe. The mix smells extreemly rich and I figured that was part of the booster problim but now im thinking something elce. pulled and cleaned all the spark plugs, they were fauled with carbon really badly. wire brushed them down and re installed and same issue. The plastic screw to my power stearing pump off the EFI broke and I extracted it out with a hot screwdriver. The problims stll persist with vacumes pluged and all. Not sure whats going on here and would love any insight. Thanks