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AC vacuum issue


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da324
User

Nov 30, 2021, 6:19 PM

Post #1 of 7 (157 views)
AC vacuum issue Sign In

Hi,
I have a 1996 Cadillac Seville. Early this past Summer I replaced everything except the evaporator, one refrigerant sensor, the low side shut off pressure valve, and the high side port After the install it held a vacuum for well over an hr. About 6 weeks later, the low refrigerant light came on and the ac shut down. I put oil with dye in and it appeared to have some in the high side port. So, I replaced that and pulled another vacuum and left it for 2 hrs and the vacuum held. 5 weeks later and I got the same message and it shut off again. I do not see any dye anywhere. Is it possible that the leak is so small that it holds a vacuum, but when refrigerant is reintroduced into the system, that leak may become worse under pressure? Is there anyway to find it? Replacing the evaporator is out of the question, Id rather put two cans in every couple of months in the summer. Thanks!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 30, 2021, 6:27 PM

Post #2 of 7 (150 views)
Re: AC vacuum issue Sign In


Quote
Id rather put two cans in every couple of months in the summer. Thanks!


If you do that you will eventually smoke the compressor.

Yes, it's entirely possible to hold vacuum and still have a leak for a couple of reasons.

First, you still have the gauges attached to the ports so that takes them out of the leak equation.

Second, many leaks are on the exterior of components and can act like a flap that pulls tight when pulled from the inside but leaks with outward pressure. Sometimes a compressor seal will act like that too.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



da324
User

Nov 30, 2021, 7:21 PM

Post #3 of 7 (146 views)
Re: AC vacuum issue Sign In

Well, I'm going to try my best to find the leak, but if it is the evap, I'll take my chances filling it a couple of times a year because the motor has to come out to get to the evap. Any ideas on finding the leak?Thanks!


Hammer Time
Ultimate Carjunky / Moderator
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Nov 30, 2021, 7:34 PM

Post #4 of 7 (139 views)
Re: AC vacuum issue Sign In

You don't really have to remove the engine, just lower the cradle but it is a very big job.

I usually don't recommend these things but Red Devil makes a pretty good sealer that works on evaps without messing the system up too much assuming you actually confirm the evap is the problem.
The dye is the best way for everything but the evap. You need a good sniffer for that and even then it could be hard to determine. Check the drain for dye. Sometimes I drill a hole in a strategic spot in the evap case to insert a sniffer. On that one you should be able to remove the resister to access the evap for testing.

The problem with continuing to run a system with a leak is that the lubrication is mixed with the refrigerant so when you run it low on refrigerant, you starve the system for lubrication and if you don't replenish it often, it makes the problem even worse.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



da324
User

Nov 30, 2021, 7:52 PM

Post #5 of 7 (134 views)
Re: AC vacuum issue Sign In

Okay, thanks. I actually knew about the cradle, but as you said, still a big job. Any idea on how much oil to add back every time I have to add a couple of cans? I have one of those injectors that can introduce the oil into the low side port. Thanks again, much appreciated!


Hammer Time
Ultimate Carjunky / Moderator
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Nov 30, 2021, 7:58 PM

Post #6 of 7 (130 views)
Re: AC vacuum issue Sign In

It's a 2 pound system so if you're adding a pound, I would add about an ounce of oil. It all depends how much refrigerant was lost.

If you are doing a complete evacuate and recharge which you should be doing, add maybe 2 ounces



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



da324
User

Nov 30, 2021, 8:25 PM

Post #7 of 7 (126 views)
Re: AC vacuum issue Sign In

Okay, thanks for the help.






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