I measured my vacuum today and the book says it should measure 10 in-HG... Mine measured 30 in-HG. I didn't figure this to be a big deal but I thought I'd ask if it was anyway.

Mike

 

I think that higher's good, right?

That seems like quite a discrepency to me. No clue what it could mean, though.

 

''No clue what it could mean, though.''

It means his vacuum pump really sucks!

...just couldn't resist

 

That's painful.


Just....

Painful...

 

Higher's better. That low figure is the minimum needed to run everything. If you were hunting a brake problem, you can now rule out the vacuum pump.

 

Just for everybodies edification, 30 inches is about how high the atmospheric pressure will force mercury into a vacuum tube at sea level. In other words if you had a 1^2 inch column of mercury it would weigh 14.7#. 30 inches is about as good as you'll ever get.

Edwin

 

Yeah, you could use that to evac the A/C system...

I think it's actually 30 inches of water, that's how most automotive vacuum gauges read.

 

A-Poc said he was getting 30" HG which is the standard abbreviation for inches of Mercury. Actually the standard atmosphere at sea level is 29.92 inches of Mercury which is why we set our altimeters to that when we're flying above 30,000 feet.

30 inches of water wouldn't be much vacuum at all since normal atmospheric pressure can force water up 34 feet! This is why the first barometers used Mercury instead of water and why vacuum is stated in inches of Mercury.

It's also why well water cant be lifted more than 34 feet with a vacuum pump.

Edwin