Vacume or Booster???

[RGMS4X4]

Hey Yall,
It's been awhile. Not much time to play on here lately.
When my truck is run at mid to high range RPMs the breaks work fine
The first time I apply them. If I let off and get back on them The pedal
is real hard to push. If I am running high RPMs and have to get on the brakes
hard then the same thing happens, The pedal is hard to push.
I need some ideas where to start.
Vacume Pump?
Booster?
Mastercylinder?

Thanks

Randy

 

[Agnem]

Randy, if you don't have a vacuum gauge as part of your instrumentation, consider getting one. It's like a big rig - you wouldn't go out on the road without knowing how much air presure is in your tank. Being able to watch the behavior of the vacuum gauge would be a big help. Based on what you've said so far though, my money is on the vacuum pump.

 

[JPR]

Would put my money on the vacuum pump. However, with the cost of the components, I would buy a vacuum gage as Mel said and run the test in the shop manual.

Test part A
Test part B

 

[RGMS4X4]

Thanks Guys
I will do the test ASAP. I hate to just start changing parts. $$$$

Randy

 

[Full Monte]

Before you go spending bucks on a vacuum pump, remove the end of the pump hose at the firewall and turn on the engine. It should give your hand a better hicky than you ever got as a teenager. It should be tough to remove your hand from the hose. Then check the grommet that goes into the vac assist unit. They leak there sometimes. Also look for any disconnected vacuum hose (like to those 3 inch round accumulators).