My truck doesn't stop......

[damemorder]

When we first got it two years ago the pedal had about a half inch of travel before braking started. Now its got almost three inches of travel. Just replaced pads, calipers and rotors are in good condition. The brakes are bled, And I can see no leaks at the wheels. Seeing leaks under the hood is almost imposible as the Oil Pressure Sender by the Distributer leaked for about ten years before I replaced it a month or two ago.

Some have suggested Vacuum Booster, But I don't know how to test that, and funds aren't readily available to test by replacing.

Others have suggested the Proportioning Valve, But I've never seen that and wouldn't know where to look for it or how to test it.

So, My question is, What is wrong with the braking system in the truck?

[Free88]

Sounds like you may be getting bypass in the master cylinder. If the brake pedal ever went to the floor all the way before rebuilding the brake system the seals are more than likely shot in the master cylinder. Same problem on the 80 my son is building and when we changed the m/c the problemwas solved. This is only my opinion and not a definite fix, but worth a try,

[corn]

If you havent been adding fluid I doubt you need to be looking for a leak. Id guess its the master cylinder, the booster only assists when the truck is running. Did you bleed the system with the truck running? Im not sure but I would think it would make bleeding easier. Also check to make sure the vacuum hose is connected & in good shape to the booster...corn

[Tom Felso Jr]

Hi,
Make sure the rear brakes are adjusted properly. That will give you a low pedal condition. Also take the 2 bolts loose where the master cylinder bolts to the power brake booster and see if it is wet if it is it means the seal in the rear is bad and will leak the fluid into the booster if it is change the master. If you need a new master make sure and bench bleed it before you install it.The master cyl could also be passing fluid back and forth between the front and rear chambers that is a internal problem If it is replace the cyl. As for the power brake booster when they go bad it usually gives you a high pedal because you have no power assist. The prop valve is bolted on the left frame rail by the front of the cab. that would be a last resort as they do not go bad very often. If you need any other info feel free to contact me.
Tom

[Grim Reaper]

I agree with Tom. Check the rears first. You have to adjust those up till they are dragging especially on new pads. If you don't your going to get a LOT of peddle travel. Make sure the adjusters are clean and move freely. It's best to leave them dry. Heat off the brakes will bake most lubricants and petty well glue the adjuster and make it nonfunctional.

Also people blow it and get the adjusters on the wrong side. There is a left and right.

If the system ran completly dry then you might still have air in the Combination valve (what most people call a proportioning valve). The rear circuit has the proportioning valve and the way the CV is mounted the line out is pointed down. It's in creddibly hard to bleed out the air if run dry.

A trick I have found is with a full reservior crack open the inlet line for the rear (head under oil pan look foward it;s the line into the top on the right) a few turns till it has a pretty good leak. Tap the CV with a wrench to dislodge the air. This will cause the master to gravity bleed so not going ot get air in it.

[damemorder]

I have no idea of the condition of the rear brakes... My uncle bought the truck new and drove it 40mi. a day until the timing chain went, I bought it and replaced the chain, It's been through two set of pads without even breaking loose the bleed screws since then. The truck has been T-Boned twice in the drivers door since I've owned it, and each time it got hit the braking was a little worse. I guess I'll go check the master for leaking.

[gchemist]

Booster testing procedure.

Brake bleeding.

[westcasey]

Also take the 2 bolts loose where the master cylinder bolts to the power brake booster and see if it is wet if it is it means the seal in the rear is bad and will leak the fluid into the booster if it is change the master.



I have this problem. Could a guy just replace the seal. Why replace the whole cylinder?

[damemorder]

Hey guys, I'm going to fix this this weekend, but i'm just wondering, What makes the brake light come on? Cause that thing is on constantly....

[Tom Felso Jr]

When the brake light is on that usually is a indication of fluid loss. In one of my earlier posts I told you how to check your master cyl. Start with that and let me know how you make out. Feel free to contact me with any questions.
Tom:
bowtie:

[TwinTurbo]

The brake light comes on when there's a pressure difference between the front and rear circuit, if your calipers/lines are not leaking it myust be the MC.

If you fix your brakes and the light is still on, stomp the pedal real hard, this will force the plunger back in the position where the light is off

[damemorder]

Ok, I put a jack on it and got the rear drivers' side tire off, I can spin the drum with the brakes on full, so I go get dad and tell him to take that apart and fix it, but he can't find the adjuster hole... he says the pads are gone and stuck inside the drums, so how do we get that off?

[damemorder]

Got the drumm off with a hammer, new shoes installed. Braking is better but light is still on.

[TwinTurbo]

Stomp the pedal hard

[Tom Felso Jr]

Hi,
I forgot to mention there is a pin in the proportioning valve that pops sometimes when you run out of fluid. You can try to depress the pin but usually on a older vehicle it sticks. When it does you need to change the valve. Then give it a good bleeding. Tom