Greeting to Everyone:

 

During a rebuild of the J25 engine in my outback, I had to disconnect the A/C. Now no cold nothing... I have the gauges to charge it,, but the question is... Do I really need to "pull vaccum" on the system before re-charging??

 

Thanks for any comments

Dan

Chicago

ABSOLUTELY...If you do not Evacutate or 'Pump Down' the system, you may leave some moisture/humidity in it. And that's not good. Can lead to expansion valve freeze up, poor performance, Receiver/dryer failure.....

Also if it was opened quickly, you probably also lost some lubricant (compressor oil).

I've done this on the side for about 30 yrs....I always pump a system down and leave it set. This is also a way to check for leaks.

I replaced the compressor on our outback and never pulled a vacuum. I just added oil and R134 and it works better than ever. If your system was open to the air for very long you will most likely need to replace the receiver/dryer and pull a vacuum before refilling.

 

FWIW opening the A/C system isn't necessary for engine removal. Just unbolt the compressor and bungee it to the left strut tower. Same goes for the power steering, unbolt it and bungee it to the right strut tower.

i always pull a vacuum as well, but my buddy in his impatient mode as normal didn't want to last year in his honda. we removed and replaced the compressor immediately, charged it and it blows antarctic air. his had retained it's previous charge though, the compressor was just inop. i agree with mentioned earlier, if it sat open for awhile you definitely want to pull a vacuum or your a/c could easily start failing soon after.

Thank you .. looks like I'll need to get it vaccumed.... not cheap... dealer wants about $200 for the vaccum and recharge... guess better get it done right the first time.. Thanks alot..... On a side note after about 3000 miles on my rebuild all going good.... except the oil thing... No leaks, no buring oil, nothing in coolant... all good,, but after a 1500 miles or so It seem like I need to add oil.. Oh well. Life goes on

 

 

Dan

A qt. in 1500 miles? Nothing wrong with that. Normal oil consumption is generally considered to be around a qt. or less per 1000 miles.

Why is it that these J25 engines "eat" oil...???? sure seems odd to me and never figured it out... What about putting in a heaver oil?

 

 

dan

new rebuild and oil consumption of 1 quart per 1000 seems like alot to me.

 

on the A/C - for 200 bucks you can go buy a compressor, buy a vaccum pump and recharge it yourself. vaccum pumps are 10 bucks at harbor freight. buy one, borrow someones compressor and buy some R134a. while everything is dry and open (your a/c system) replace BOTH schrader valves. they cost about 50 cents and require venting the system to replace, so replace them now before you charge it up. replacing o-rings would be nice too, but there are a bunch of them. definitely unscrew the two schrader valves on your compressor and get new ones. (valve removal tool is like 2 dollars, same thing for tire stem valves like in a bicycle or car tire). call around you can probably find somewhere a little cheaper than 200 if it's R134a.

Thanks for the info about buying a vaccuum pump.. Have a compressor already.. Saving a lot then... Oil comsumpution is about .5 qt every 1500 miles... but as I said, no buring, no leaks, nothing in coolant... A Mystery. :-\ !!

 

 

D-

Re consumption, be sure to check PCV valve. Had a neighbor with a 97 Legacy. Dealer just did 90K service and told them same about oil consumption. When I checked PCV valve, it was clogged and cruddy. Cleaned it up with kerosene and they are down to 1/2 qt by next oil change.

 

Dealer Service Depts are like everything else, some are incredibly good, others make me wonder how they stay in business ( I know, I know...They sell new cars instead of doing a decent repair).

A tip I learned from an AC tech that came to my house one time is to pump nitrogen into the system to dry everything out, THEN pull the vacuum. That way, everything is dry.

1/2 qt is nothing. Gotta remember that as your oil gets hot some of it is vaporized and vented and/or burned through the PCV system, as well as normal combustion in the cylinders. The oil ring leaves a very small amount on the cylinder walls for lubrication, not all of that is removed by the compression rings, so some of it is burned during normal combustion cycles. Not to mention that every engine has at least a small leak or drip somewhere.

All of that adds up to normal oil consumption/loss. I've been a mechanic for most of my life and my Dad was one of those legendary guys who could troubleshoot and fix anything that burned gas. He always told me, as have many other very reputable mechanics, 1 qt or less in a 1000 miles is just normal oil consumption. Remember too, that if you just did a rebuild that included rings it will take some time for them to seat and you will have a bit higher oil consumption until they seat. There's no such thing as an engine that doesn't use some oil.