I finally had some short amount of free time to work on it last night. So when I pulled the check valve and plugged it then started the truck the pedal firmed right up. When I put the check valve back in same symptoms come back. I didn't drive it like this though just driveway tested it in park... I will try and pull vacuum line tomorrow to test if its the line or check valve. Also does anyone know what the tiny little hose connected to the check valve is for, or what it even runs to? Could that be the culprit? Also a buddy of mine stated that I should test the booster by pulling the vacuum line or check valve and driving around the block like this... Thoughts?

 

When you disconnected the check valve the pedal firmed up because you no longer have power brakes.

The smaller line is for your HVAC controls - since you haven't posted the year of your truck I can only assume it is a '97-00.

 

Oh ok, Thank you. Yes sorry I forgot to mention the year. It's a 2000 with the 4.7 ext cab sport. How will I know if it's the check valve that's going bad or has gone bad... Also the HVAC wouldn't be the culprit, would it be?

 

No, it's not the HVAC causing the problem.

The check valve allows you to have some power braking if the engine is off/stalls.

Having to "pump up" the brakes indicates air in the system.

 

More than just 1997-2000 have the HVAC off the check valve - my 1988 has both HVAC !AND! the cruise control servo off the check valve (wonky, I know ... )

As to driving around - that's your choice. Do remember, no power assist for brakes. So you MAY have problems stopping in time in case of a panic situation (like Johnny Droptables runs out from around his parent's Prius chasing a ball ... )

RwP

 

Yes, it runs the cruise control servo too, if you have it.

 

Thank you guys for all your help so far... and replies for that matter. So I did drive it around out in the middle of a dirt road going very slow with the check valve off first, then the brake booster off. The problem is still there with both of them out. So I was wrong.. The pedal does not stay firm at all and falls to floor quite easily still with the check valve pulled and plugged. I'm thinking the MC has to be bad. I agree with the air in the lines, but it's no pumping the brakes per se... in order to brake properly. It's hard to explain. A few pushes of the pedal the pedal firms hard and dies off again, but in between the pushes of the brake pedal the pedal doesn't slowly firm up in between the pedal falling and the hard grip of it, if that makes any sense. I have bled the system a number of times properly to ensure that there is no air what so ever in the system. Last resort I suppose is to take to a shop here in town...

 

Before you take it to the shop, replace the master cylinder and pressure bleed it (or vacuum bleed it).

Also, be aware if there's any brake fluid between the MC and the booster, the booster is done for. I'm of the "It's old enough, replace it ANYWAY" mind set, but it's your money, not mine, being spent *grins*

RwP

 

If you didn't bleed the system with a DRB (scan tool) you did not bleed the system properly - sorry to say.

You can't cycle the valves.

 

Just an update... I replaced the MC and the booster along with new bleeder screws cause the old ones were shot. Bench bled the MC and got everything installed. My son helped me bleed the system properly and voila' I have brakes! now the last step is to get it to the local dodge dealership in town and have them run it on the DRB to cycle the valves so the brake and ABS light can be reset. Thanks guys for all your help and patience! this my first Mopar and I cant wait to get it on the road!!