Vacuum

[metrobillyg]

1988 Ford Ranger 4X4 STX extended cab. I had little brake pedal, newer pads, and calipers in front newer shoes in rear, no leaks. Replaced booster and master cylinder still not much better after bleeding entire system. Did some reading and it was suggested that the vacuum pump could be the culprit but don't know what it looks like or where it is located, can't find it listed in the chilton manual as vacuum pump? According to a video I found it seems simple to test but
where is it?

 

[Spott]

Vacuum pump? The engine itself is the "vacuum pump" which supplies vacuum to the hoses. The only way you're not getting vacuum is if you have a vacuum leak somewhere in the system, which would make your engine run poorly.

To test if it's a vacuum leak, unplug your IAC (small silver cylinder just to the side of the top center air manifold, kinda opposite the throttle linkage, has a 2-wire connector) while the engine is idling. The engine should lug way down to 500rpm or even stall, if you don't have a vacuum leak. If you do have a leak then the engine will continue idling smoothly when you unplug the IAC. To get more measurable results, you can get a vacuum gauge and connect it to the vacuum system, with the engine idling. You should see a fairly smooth, steady reading of 18-20 "inches", IIRC.

 

[RonD]

+1 ^^

Diesel engines often use vacuum pumps to operate power booster or other vacuum accessories.
Gasoline engines have vacuum in the intake manifold so no pump is needed.

Unclear about "little brake pedal" meaning, though?

Pedal goes way down before stopping vehicle.
Pedal is touchy, a little pressure locks up brakes.