Vacuum pump question

[mexicanjoe]

i used a vacuum gauge to measure my 89 7.3 n/a pump. Turns out it topped (bottomed) out at 22" of vacuum. Is this sufficient for this unit? The reason I ask is because I can get 2 good stops on my brakes before it starts to get difficult to depress the brake pedal again. New master cylinder/brake booster , or is this normal? I have everything to do a rear brake job in the future including springs..... let me know your thoughts....... su amigo:
mexicanjoe!

 

[riphip]

Joe, do you have someone that can press the brake pedal 3-4 times and hold while you check the vacuum?

 

[austin92]

Did you check right off the pump or at the brake booster? Was the needle jumping on your gauge or steady?


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[mexicanjoe]

I checked it with engine running at the firewall. And if held the vacuum for several minutes afterward...

 

[austin92]

I checked it with engine running at the firewall. And if held the vacuum for several minutes afterward...

You could check it at the booster and see if there’s a leak between it and the firewall. Does all your vents change ok and cruise work?


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[Macrobb]

I checked it with engine running at the firewall. And if held the vacuum for several minutes afterward...

Probably the pump can make vacuum, just not move a high volume of air(needed to "recover" the vacuum quickly) anymore.

I'll bet it's the vacuum pump being fairly worn and the reed valves inside it not sealing correctly.

 

[mexicanjoe]

All the vents work, the cruise does not. I have to find an adapter to check the booster though

 

[Oledirtypearl86]

I'm with @Macrobb I. Think the vac pump is in failur mode if you are unable to maintain enough vacuum during high demand kind of like a small air compressor you can run that 3/4 inpact gun just fine but you. Loose all your power fairly quickly but give it a few and it's right back to full power

 

[IDIBRONCO]

I'm with @Macrobb I. Think the vac pump is in failur mode if you are unable to maintain enough vacuum during high demand kind of like a small air compressor you can run that 3/4 inpact gun just fine but you. Loose all your power fairly quickly but give it a few and it's right back to full power

Good description.