Vacuum pump, assist for brakes, diesel engine

[rbh]

So the old 91 f-250 pick me up truck with the 7.3 non turbo has been loosing braking ability for the last week or so
Lets call it brake fade.
It brakes well when the engine is revved up, but idle is not good or I do multiple brake applications and can feel the brakes loosing that assist feeling,

whats the odds the vacuum pump is going/shot.

(I have looked for leaks/lines off and can't find any,"I will do a vacuum test as soon as I can find a gauge"

 

[rbh]

Re: Vacuum pump, assist for brakes, diesel engine

I can hear you typing PJ.

 

[puddle jumper]

Re: Vacuum pump, assist for brakes, diesel engine

You got good ears.

Look for a loose belt on the air pump.

Check the pump with a vacuum gauge to make sure you are getting good vacuum I would think about 17 to 20 inches of vacuum would be right

with a vacuum pump check to see if the brake booster holds vacuum.

Are you sure your truck does not have a Hydropower assists system that uses the power steering pump?

 

[Mntom]

Re: Vacuum pump, assist for brakes, diesel engine

If you have that big of a leak then you should have defrost only for the heater control. With a loss of vacuum the hvac 'defaults' to defrost. If you have all functions chances are you are getting good vacuum. Next check the big hose that goes to the booster. I have seen more than one fail on the inside and look fine on the outside.

 

[TilliamWe]

Re: Vacuum pump, assist for brakes, diesel engine

What vacuum pump? They use vacuum pumps for their brakes, and not the power steering pump like a Chevy? Seems silly, when there is nothing else vacuum on a diesel, cause they don't make vacuum like a gas engine.
rbh, Harbor Freight has a inexpensive vacuum tester for about $15. 20% off coupons in the paper today too.

 

[rbh]

Re: Vacuum pump, assist for brakes, diesel engine

What vacuum pump? They use vacuum pumps for their brakes, and not the power steering pump like a Chevy? Seems silly, when there is nothing else vacuum on a diesel, cause they don't make vacuum like a gas engine.
rbh, Harbor Freight has a inexpensive vacuum tester for about $15. 20% off coupons in the paper today too.

YUP, ford has a small vacuum pump, belt drivin, it runs the heater vents and the brakes (booster).

Found my vacuum tester today just have to adapt the plumbing fixtures to fit.

One brake application at high idle, great braking feeling in the pedal, next one pedal is hard to push???

 

[TilliamWe]

Re: Vacuum pump, assist for brakes, diesel engine

Thanks for the education.

 

[dolluper]

Re: Vacuum pump, assist for brakes, diesel engine

The check valve leaking at the brake booster....or filter if you have one on the line ....line itself