1999 4.0L p38. 115K on the clock. Everything seems to function. The truck is an absolute BEAST off road. My problem is when I press the brake pedal I hear an electric motor run for just a second and then stop. Also when I press the brake the BRAKE, TC, and ABS lights all come on for just half a second and then go off. I'm pretty sure it's all working because when I get in some slick stuff I can hear the "thump, thump, thump, thump" sound coming from the dash and truck comes on out of the mud. What do y'all think is the matter?

 

The brake system is electro-hydraulic, what you're hearing is the brake booster pump. It should not be coming on how it is when you hit the brakes, the lights coming on are an indication of the fault. The pump itself si working if the lights go right off, and the truck stops. There is a Nitrogen filled accumulator on the pump that is replaceable, the accumulator essentially pre-charges the system so the pump doesn't run all the time. It sounds like yours is bad, when you start the truck, are the three lights on, and it takes a few seconds before you have brakes? It's pretty simple to replace, but you should bleed the entire system at the same time, which is not the easiest system to bleed properly.

 

How pricey is this accumulator? Got and good cheap sources?

 

The cheapest I can find it is 245 dollars. Is there anything I can do to my existing accumulator to make it function better. Any kind of maintenance?

 

That price is about right. But no, there is nothing you can do to fix it, and i don't suggest trying, it's under high pressure, almost 1200 psi.

 

Thanks for sharing but i had a issue a coupe of years back that time i bring the vehicle to garage they changed accumulator then problem fixed but after some time again it is happening . i do not know why..i did not do anything with that and after few month i replaced my vehicle..

 

The accumulator on a P38 is basically a maintenance item. If you ignore it you will cook the pump that pressurizes the brake system and that is way more expensive than $245. You should replace the ABS relay at the same time. If that sticks (and they do) it will also cause you pump to cook. If you blled the brakes, make sure to follow the procedure in RAVE exactly and also use only Castrol LMA.