Well last weekend I replace the rear brakes calipers, pad and rotors bled it and drove it all week long about 300 miles with no issues. Then last night I jumped in the truck and started it and took off and hit the pedal and nothing pedal went to the floor before I got very little pedal to stop. So I released the pedal and hit it again it was fine then repeated the process nothing hit it again fine, so I parked it. Came home from work today drove it around the block nothing at all this time....... I looked under the truck no leaks of brake fluid, checked the fluid level it was full so what going on? Is it my vacuum pump?
No it's not your vacume pump. The small electric vacume pump is for the HVAC system and autolocking front hubs. It has no function with the braking system.
The power boosting for the brakes comes from the power steering pump.
My guess would be your problem is something related to the master cylinder. Either it's bad, or there is air in it.
How did you bleed your brakes? I used a vacume bleeding system I put together, so there wasn't any pumping the brake or repeated messing with the bleeder screws. The only issue was ensuring the master cylinder fluid level stayed high enough where it didn't suck air.
I suppose there could be something with the ABS system, maybe it has air in it??
