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5 cfm Max Vacuum?

CF6Mech on Tue April 08, 2008 1:18 PM User is offline

Year: 1994
Make: Chevy
Model: Pick-up
Engine Size: 4.3
Refrigerant Type: 134a

Ok guys, I need some help. I purchased the 5 cfm dual stage pump so I would be sure I could pull a GOOD vacuum on my cars before adding the freon. Well, after letting the pump run for almost a hour and a half it only pulled 28 in of vacuum and after 20-30 min. the pump starts sort of rattling every so often. Any suggestions. I've got another car lined up for this Saturday and I would hate to have to redo it.

Chick on Tue April 08, 2008 1:35 PM User is offlineView users profile

what is your elevation, and are you using just the guage set to measure HG's? Make sure the guage is 'zeroed" before you start...
You lose on HG for every 1000 ft above sea level

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

CF6Mech on Tue April 08, 2008 3:49 PM User is offline

I didn't think to check the gage for zero. I will do that. I am only at about 350 ' above sea level (Memphis Tn). I have seen the term "microns" used for measurements approaching absolute vacuum at 30 in. How is that measured?

Chick on Tue April 08, 2008 3:59 PM User is offlineView users profile

You need a micron gauge.. Absolute vacuum is 29.9 at sea level..there is a chart, maybe posted on the board somewhere, you can do a search, but remember, the gauge reading is not that accurate, a micron gauge is...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

brickmason on Tue April 08, 2008 8:42 PM User is offline

CF6Mech,

I have the same pump bought from ackits and it has the same sort of rattle you mentioned after it has almost reached full vacuum. Have used mine for 3 years with no problems and it pulls down to the 15 microns the manufacturer states as I have checked mine with a micron gauge.

Remember to open the little brass knob on top about a quarter round untill it reaches 26 or 28 lbs. depending on elevation as Chick stated because you lose an inch lb. for every 1000 feet above sea level.
Opening this valve keeps mass amounts of moisture from entering your vacuum pump oil during the first part of the vacuum because thats where most of the air and moisture is, then close it to finish pulling a deep vacuum.

Just change the pump oil as the manufacturer suggests and you should have a pump that will last a long time.

As far as working outside,I also like to keep mine out of direct sunlight, especially in 100 degree weather and even place a fan in front of it to help keep it cool to prolong the life of it.



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Just another brick in the wall

Had a little mule I fed him castor oil and every time he jumped the fence he fertilized the soil

CF6Mech on Mon April 14, 2008 12:17 PM User is offline

Well, I got the parts replaced and hooked up the pump. It went to 28 in....and stopped. The BRAND NEW micron gauge never moved below 100,000 microns. Unhooked the car and gauges and hooked the micron gauge directly to the vacuum pump. It still never moved. Of course before all this I had loaned out the pump a couple of times. I went to drain the old oil and add some fresh oil to the pump. I only got maybe a quarter to a half of a cup of oil out of the pump. I have a sneeking suspicion that the pump may be scored. Anybody know where I can get a Mastercool vacuum pump rebuild kit?

mk378 on Mon April 14, 2008 1:22 PM User is offline

On many pumps, the oil seals the exhaust valves. It won't pump properly unless full of oil. First refill with clean oil and test it.

CF6Mech on Mon April 14, 2008 1:35 PM User is offline

I did, but I'll try again tonight.

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