i don't drive my truck very much any more so i really don't put too much importance to my problem yet.... when i shut the engine off , i have no brakes to speak of. i used to have at least three applications before the pedal would get really hard, now it's hard the first push and hardly any stopping force... i can push with both feet and maybe can stop if i'm barely moving........i have an idea what the problem is but i need a second opinion------------

 

Vacuum leak would be my guess, I know the system is hydroboost but after I fixed my vac leak at the firewall mine quit doing that.

I also replaced the PS fluid at that time IIRC....

 

can you tell me where vacuum is tied to the hydroboost, it must be be, because i don't think hydraulic pressure can be stored ....vacuum must be involved, hmmmm, there must be a vacuum storage canister somewhere in the system i guess i'll get my glasses on and go look at all the vacuum hoses and connections. maybe i'll spot something
if i find anything i'll be sure and post it!

 

Hydro boost is powered by power steering pump...
Vacuum pump supports speed control, 4WD engagement, and heater controls.
A accumulator (the blue cylinder) on hydroboost stores hyd pressure after shutdown or engine stall...It can give you up to three assisted stops when good. Can you now read between the lines?? The accumulator is serviced with hydroboost assy.

 

I was wondering about that too...Sometimes after a day or two sitting, my truck has a hard brake pedal and no ssist right before start up.

I notice it more on my sloped driveway when I pop the ebrake as I wait for the light to go out....other days it squishes down like a vacuum system and gives me a good hold.

 

according to my research there is a VERY stiff spring in the accumulator that pushes a piston against the hydraulic brake system when there is no normal brake operation (engine stopped) any time the the engine is stopped the spring will cause the brakes to be "normal" up to 3 brake applications..... so i'm thinking the check valve is bad or possibly the spring is weak or broken, altho i think the spring is not an issue, so that leaves the chk valve which is in the accumulator/hydroboost assy

 

BOOSTER FUNCTION TEST
With the engine off depress the brake pedal several times to discharge the accumulator. Then depress the brake pedal using 40 lbs. of force and start the engine. The brake pedal should fall and then push back against your foot. This indicates the booster is operating properly.

ACCUMULATOR LEAKDOWN
Start the engine, apply the brakes and turn the steering wheel from lock to lock. This will ensure the accumulator is charged. Turn off the engine and let the vehicle sit for one hour. After one hour there should be at least two power assisted brake application with the engine off. If the system does not retain a charge the booster must be replaced.
With the engine off depress the brake pedal several times to discharge the accumulator. Grasp the accumulator and see if it wobbles or turns. If it does the accumulator has lost a gas charge and the booster must be replaced.

 

i'll go out and try the tests right away

 

it passed the booster test but failed the second test! i think the pressurised gas has lost it's ability to keep the pressure. it's not loose, so it must have bled off

so what's next? how long can i expect to drive before the brakes fail completely? like i said before, i don't drive the dodge very much any more ...maybe 1000 miles a year if that. i live out away from civilization. 200 miles from SLC UT...the nearest town is 50 miles and they have 3 stop lights ,so as you can tell i don't drive in traffic with the dodge..............the mileage i have on the truck now ,271000 is a lot of go but not too many stops i'l probably use it for going for firewood in the mtns