Hello everyone..

I am planning to purchase a vacuum pump from HarborFreight.com. The difference is about $50 between a 2.5 and 3 CFM units. The 3 CFM is a two stage unit - which I dont quite understand. Why should I purchase the 3 CFM and not the 2.5? Will the 2.5 do the job.

My autozone does not rent out vacuum pumps. Besides..I have money . I hope to loan this out to forum members in the Los Angeles / San Fernando Valley area.

Thanks for your advise.

 

Neither one is adequate to properly boil off all of the moisture in the system. You want a minimum of 5-6 CFM and 7cfm is absolutely ideal. (though probably overkill for a DIY'er) The point of the vaccum is to pull air out of the system and more importantly boil off any moisture(very damaging to the AC system) An AC system has many crevices for air and moisture to hide.

 

I use the 2.5 and have no issues whatsoever.
Just make sure you are pulling a vacuum with either one you choose and make sure
It holds a vacuum once finished. Also make sure you are using gauges.

 

I guarantee you are not completely removing all the moisture. But what ever gets you by is good enough for most people....

 

I don't understand. It's not the flow of the pump that boils off moisture, it's the vacuum... Right? Why would it matter how many CFM it flows if it is capable of pulling a vacuum through the whole system that is adequate to boil off moisture? Wouldn't a smaller pump just take longer to pull an adequate vacuum? Both of the pumps claim they can get to under 100 microns which is more than enough to boil water even at freezing ambient temperature.

 

A low CFM pump will take much longer to rid the system of moisture and air. At least 3 to 4 hours or longer with a 2 or 3 CFM pump on a mid-sized vehicles AC system. So while technically a lower CFM pump will work, it will only do so if given enough time.

 

100% false, cfm has nothing to do with how deep a deep you can pull. Cfm has to do with how fast you get there.

 

Yes that was clarified in post #6.......genius.

 

actually it wasn’t. It takes no where near 3 hours to pull an automotive system below 500 microns with a 3cfm vacuum pump. My 3cfm pump pulls 118’ of 5/8” lineset to 500 microns in about 3 hours.

 

Any information I posted is easily verified in this day and age,for anyone willing to do the leg work.

Arguing with a "genius" who brought up a 9 year old thread is beneath me.....

 

there was no argument, you were 100% wrong and I pointed it out.