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View Full Version : A/C - Pulling a vaccum without an external pump



matchframe
05-31-2012, 08:22 AM
I replaced the drier and vacuumed/charged the system yesterday. I don't have a vacuum pump so I did that the old military way.... I used the engine vacuum to pull the system down. Only problem with doing it this way is the deepest pull you can do is about 25-27 pounds. Ideally you need to pull the system down to 30 plus pounds.

I found my old A/C manifold which is old school R-12. I cleaned it up and converted it to R-134 with new hoses and adapters.

http://i10.photobucket.com/albums/a122/matchframe/BDG/Jeep85.jpg

Here is a vacuum port I connected the A/C manifold to:

http://i10.photobucket.com/albums/a122/matchframe/BDG/Untitled-3.jpg

I changed the manifold connectors to accommodate the vacuum hose which connects to the engine intake manifold:

http://i10.photobucket.com/albums/a122/matchframe/BDG/Jeep84-1.jpg

Here is the complete set up:

http://i10.photobucket.com/albums/a122/matchframe/BDG/Untitled-4.jpg

I ran the engine for about 30 minute at about 2,800 RPM

http://i10.photobucket.com/albums/a122/matchframe/BDG/Untitled-6.jpg

Showing the vacuum:

http://i10.photobucket.com/albums/a122/matchframe/BDG/Untitled-5.jpg

I closed off the manifold and the vacuum held for about 30 minutes. I then charged the system and it blows cold air. I still sort of feel like I may be chasing a small leak later, but I guess time will tell.

may pop
06-01-2012, 04:04 PM
Great idea! Some other sites give the method of wasting a can by shooting it into the system while holding the high side port open. A moment after the refridgerant comes out close the port and you have pugred out most of the air. Probably leaves some air or moisture in the system. Myself Im to cheap to do it that way. I dont like wasting a can of 134.
Ron

frontsideblunt
06-01-2012, 04:58 PM
I have put a lot into my AC. It's still not 100% but it's getting there.

armmata
06-01-2012, 08:06 PM
that a hell of idea going to have to try it got to put a new condenser on mine before is gets to hot

XJexpedition
07-11-2012, 10:32 PM
If you have an air compressor you can get a venturi style vacuum puller at harbor freight for cheap. Also places like Autozone and Discount have them in their "loan-a-tool" program which is better. The harbor freight needs a decent sized air compressor that can do 4.5cfm+@90psi for about 5minutes to get the recommended vacuum. My 20gallon 5.5hp does an alright job with the harbor freight venturi pump.

Harbor Freight Venturi Vacuum Pump $15.99 (http://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connectors-96677.html)

Harbor freight also sells electric ones which are the ones you get from the loan a tool program for just over $100, and can actually get it under $100 if you get a 20% off coupon which you can get pretty much anytime.

BlueXJ
09-25-2012, 12:19 PM
I have been working on vehicles for 50+ years and have never heard of this method for a vacuum before. Thanks so much for the idea. I wonder if I can use the intake on my OBA to do the same thing????

matchframe
09-26-2012, 07:14 AM
I have been working on vehicles for 50+ years and have never heard of this method for a vacuum before. Thanks so much for the idea. I wonder if I can use the intake on my OBA to do the same thing????

You should be able to. The engine vacuum will not pull as deep a vacuum as a pump, but it does work well. One thing to be careful of is if the temps are hot outside when you use the engine vacuum, be sure to have a shop fan blowing on the radiator to help keep the engine from getting too hot. Since the rpms are at around 2,800, (what I found to be the optimal rpm for the deepest pull from a 4.0) the vehicle think it is cruising down the road expecting air to be forced through the radiator. I have done this without a fan and the engine would get pretty hot. Be sure to keep an eye on the temp gauge.

GergaffXJ
05-03-2013, 09:47 PM
What a BRIGHT idea!! The harbor freight venturi method worked for me as well.

ranchand58
05-17-2013, 06:42 AM
After replacing a leaking shrader valve, I plumbed the air intake side of an old air compressor to the low side ac in my 2000, and it worked! Re-charged the system afterwards and it continues to cool after 5 weeks...:beer: