What does the Vacuum pump do?

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May 14, 2015 | 10:11 PM

#16

wtroger

Cargo Master

Joined: May 2001

Posts: 3,208

Likes: 13

Actuall the pumps do have oil in them. The driven shaft has two sets of caged needle bearings that it runs on and the cavity is filled with oil. The older ones actually had a plug on the back you could take out and add oil. I doubt if anybody ever did. I Have put new bearing in them.

May 14, 2015 | 10:30 PM

#17

madpogue

Lead Driver

Joined: Oct 2003

Posts: 8,476

Likes: 37

From: Madison, WI

Quote:

Originally Posted by genscripter

How much vac do you need to pull? This one on ebay claims 18-22inHG:

It's not just the level of vacuum, it's the volume rate. Analagous to a compressor. Air tools require not just a certain pressure (psi), but a certain volume rate (cfm). The power brakes require something like 20 inHg, but they have a pretty high volume requirement (don't know it off-hand). Running the brakes off an electric vacuum pump would require some research into that; certainly the pumps used in the later trucks (SuperDuty PSDs) wouldn't be up to the task, as they've gone to hydroboost for those trucks.

Hydroboost would be a way to eliminate the vacuum pump for the OP, but it wouldn't help the above-mentioned hypermiler, since it's still dependent on a belt-driven pump. Any hypermiler should think long and hard about the risk vs the benefit of any efficiency mod that involves a critical safety system.

May 14, 2015 | 11:22 PM

#18

genscripter

Cargo Master

Joined: Oct 2012

Posts: 3,072

Likes: 48

From: California

Quote:

Originally Posted by madpogue

Any hypermiler should think long and hard about the risk vs the benefit of any efficiency mod that involves a critical safety system.

I agree. Most of these hypermilers do crazy stuff like kill their engines to save fuel, even while driving high speeds. Also they take corners at 30mph and refuse to accelerate. They are ridiculous.

May 15, 2015 | 03:31 AM

#19

IDIoit

Fleet Mechanic

Joined: Apr 2015

Posts: 1,264

Likes: 7

IMO i would never trust an electronic vacuum pump for my brakes.
as stated... hydroboost time, then run the electric vacuum pump for the little stuff.

Jan 31, 2025 | 08:30 PM

#20

Og74

1st Gear

Joined: Jan 2025

Posts: 1

Likes: 0

Quote:

Originally Posted by dtgl90vt

Well I wanted to delete it but I guess that's not an option cause I like having brakes. Anyway I got a bunch of parts from the engine bay ready for paint so that's exciting cause its pretty ugly in there now. Does anyone know what kind of oil was in the vacuum pump that I spilled?

Thanks again,
Devin

gear oil, I use the same stuff I put in my diff

Feb 3, 2025 | 01:09 PM

#21

knottyrope

Lead Driver

Joined: Apr 2016

Posts: 7,182

Likes: 1,337

From: Bahstun

I hope he figured it out ten years ago .............

Feb 3, 2025 | 01:44 PM

#22

dtgl90vt

Thread Starter

Laughing Gas

Joined: Oct 2012

Posts: 755

Likes: 3

From: Rockport MA

Hehe, yeah i figured it out, don't quite remember the details, but found a picture of it back in with fresh blue paint later that year (bottom right, behind horn).