Hope someone can help.
I have a 87 Dakota v6 2wd. I have replaced shoes, wheel cylinders, master cylinder, booster and three lines that were rusted, bled brakes multiple times no air just straight fluid. Firm pressure until I start it and the pedal goes to the floor. The new booster came with the check valve. I was watching a you-tube video on vacuum lines and noticed something different with mine. The booster check valve has three nipples for vacuum lines, two are vertical and one is horizontal sticking straight out (that is where my line from the intake/carb was connected) The two vertical connections were capped off on the old booster. Does it matter on the check valve where the vacuum line is attached (horizontal nipple or one of the vertical nipples. (the You Tuber had his from the manifold/intake/carb connected to the vertical nipple towards the passenger side of the valve) I am also thinking that with the new booster and master cylinder that the booster push rod is too short.
Any help or assistance is appreciated
Desmond

 

I am not a brake guy so can't answer your question. I do suggest you try the vac hose on all of those nipples while blocking off the others to see if it changes anything. I would put it back together as it was when I took it apart. then there is always the possibility of the new one being bad out of box.

 

Thanks ill try that

 

No clue why they put more vacuum ports on that check valve, I don't recall seeing ANY vehicle that had more than one vacuum line going to the booster...... Still and all, hook the line to the fitting it fits, and call it a day. If you are getting vacuum assist, then it works as intended, if you aren't, then you need to worry about it.

Does the truck have any flavor of ABS? Did the fluid reservoir ever get run empty? The one time I had a similar issue, (good brakes with engine off, no brakes with engine running) I still had a leak..... (in my case, it was because I didn't tighten down one of the lines enough......)

 

Yeah I agree, but i think the other two fittings are for optional crap. The owner before me messed with the truck, the original problem with the truck was the master cylinder was leaking on the back of it, so he cut off the rear brake line (The front side of the MC feeds the back) so it ran out of fluid, so i figured that the fluid damaged the booster. The master cylinder is new and bench bled, new wheel cyl and shoes, three new lines. No signs of leakage anywhere plus the MC is staying full, checked and double checked for leaks and no sign. Not sure about ABS if the truck does or doesn't have it, would ABS malfunction cause that problem with the pedal, if so whats the fix for it.
One of my issues and the reason Im replacing parts is I have no idea what the previous owner did with the brakes.
The vacuum line will fit on either of the fittings so im gonna switch it and plug the other two just to eliminate that possibility When i pull it off the booster there is lots of suction on the hose, the truck rev's when i put my finger over the hose off the booster. Ive seen posts about this problem with the first gen Dakotas. Hoping someone has solved it or knows something ive missed.
Appreciate the help and suggestions.

 

Just as a note -

The three ports on my 1988 check valve go to:

1) Biggest - to intake manifold.

2) Middle sized - to cruise control servo.

3) Smallest - to feed the HVAC system.

I've seen several with more than one port on them, to avoid adding a vacuum distribution manifold.

Does the brake go to the floor immediately when you start the truck, or does it just not feel any resistance?

In my 1988 FSM, it doesn't state how long that push rod should be.

I will say that if it drops immediately, or it stays down, your booster is bad (even if new!)

RwP

 

It goes right to the floor as soon as it is started. There is a little bit of brake but almost all the way to the floor

 

Goes to the floor even if you haven't pushed on it any? If so, it's 100% a bad booster.

RwP

 

If you pump the pedal, does it stiffen up any??

 

WIth the truck off the pedal is firm when I pump it. it pretty much goes to the floor when its started when I push it. I can build a little bit of pressure but not alot, we drove the truck from where we bought it, it feels like it has about 10% brake and 90% travel