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SilverStreak02

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The AC on my 2002 Lightning hasn’t blown cold for a LONG time. It had a leak somewhere that I never really worried about fixing. Well I decided to fill it up today.

I got it all filled up nicely and got the air blowing ice cold. When I turned off the engine: After several seconds I hear a loud hissing sound coming from under the truck. This sound only last about 5-6 seconds and then suddenly stops. I hooked the gauge back up and noticed the pressure dropped a few pounds.

I crawled under the truck and tried to find the source of the sound. The only thing I can figure is that it is coming from a crimp on the low side hose. The pipe where it turns to go to the compressor was wet, It was the ONLY place on the entire truck that was wet.

The fact that the hissing is delayed and also temporary has me puzzled.

What are your thoughts on this? Bad hose crimp? Should I replace it?
 

L-Bronco

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I realize hat this thread is 5 months old, but, better late than never!
The temporary hissing sound from your A/C is most likely the pressures equalizing between the low and high sides after you shut it off. (That's why it stops after a few seconds) Its hard to be certain without seeing it.
As far as the hose goes, (Not sure if you replaced it or not), if not, just spay a dish soap and water solution on the suspect area on a hot day before you start the truck and look for bubbles. (The pressure the system follows the temp, so hot day = higher pressure and better test results)
On that note, the pressure being lower after it stopped hissing is quite normal as well because the low side of the system (In the dash) is cold and the average pressure on the gauges will drop a bit.
Hope that helps.
 

SilverStreak02

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I realize hat this thread is 5 months old, but, better late than never!
The temporary hissing sound from your A/C is most likely the pressures equalizing between the low and high sides after you shut it off. (That's why it stops after a few seconds) Its hard to be certain without seeing it.
As far as the hose goes, (Not sure if you replaced it or not), if not, just spay a dish soap and water solution on the suspect area on a hot day before you start the truck and look for bubbles. (The pressure the system follows the temp, so hot day = higher pressure and better test results)
On that note, the pressure being lower after it stopped hissing is quite normal as well because the low side of the system (In the dash) is cold and the average pressure on the gauges will drop a bit.
Hope that helps.
Thanks for the reply. I have not replaced the hose yet. Nor have I really worked on it since this post. I’ll take your advise and see if I can find the leak.
 

L-Bronco

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No worries, one last thing, if you cant find a leak, there's a good chance it could be the compressor seal. They have 2 ceramic discs together that create the seal, (that's a bit simplified, but accurate enough), they rely on oil between them to form the seal. If it doesn't run for extended periods, it will dry out and leak. It has been a problem since the switch to R-134A. Make sure the compressor runs every couple months and it should be better. Replacing the seal/ compressor wont change things if sitting is the issue.
Cheers
 

L-Bronco

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Sorry Guys, just to be clear, if the seal failed, running it wont fix it.
Running them periodically will keep oil in the seal, this will help to keep it from leaking.
It will often stop leaking if lack of oil was the only cause of the leak.
Up here our "nice stuff often sits in storage for 6 to 8 months waiting for the roads to be clean. It's common to lose part of the charge over the winter if you don't cycle it a couple times with no leaks after its serviced.
They aren't all like that either, it really depends on seal design.
Sorry for the confusion.
 

SilverStreak02

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Sorry Guys, just to be clear, if the seal failed, running it wont fix it.
Running them periodically will keep oil in the seal, this will help to keep it from leaking.
It will often stop leaking if lack of oil was the only cause of the leak.
Up here our "nice stuff often sits in storage for 6 to 8 months waiting for the roads to be clean. It's common to lose part of the charge over the winter if you don't cycle it a couple times with no leaks after its serviced.
They aren't all like that either, it really depends on seal design.
Sorry for the confusion.
I truly appreciate the feedback.
 

MG0h3

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Oreilleys has a cheap UV light kit that used on my beater Focus.

Ironically, front seal on compressor was toast.

Couple orings has some color too.

I left the auto repair industry right when we were getting AC equipment, so I tapped a friend for knowledge.

He said always do the dryer and expansion valve when the system is open.

Rented gauges from Oreilleys.

Too easy.

And the expansion valve was 40% plugged.


Sent from my iPhone using svtperformance.com
 

SSSSSSSSSSSSVT

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Run the UV light leak refrigerant stuff. Its easy to spot if its coming from a hose or the fill valve. If you cant find the leak using that its 100% evaporator core. If its that plan a weekend and brush up on your curse words.
 

GerryMX

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No worries, one last thing, if you cant find a leak, there's a good chance it could be the compressor seal. They have 2 ceramic discs together that create the seal, (that's a bit simplified, but accurate enough), they rely on oil between them to form the seal. If it doesn't run for extended periods, it will dry out and leak. It has been a problem since the switch to R-134A. Make sure the compressor runs every couple months and it should be better. Replacing the seal/ compressor wont change things if sitting is the issue.
Cheers
My friend is looking to get this Lightning and the owner mentioned he's been hearing a hissing sound intermittently. We'll take a closer look at it this coming weekend after we finish installing the exhaust and cold air intakes on the Silverado.
 

SilverStreak02

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No worries, one last thing, if you cant find a leak, there's a good chance it could be the compressor seal. They have 2 ceramic discs together that create the seal, (that's a bit simplified, but accurate enough), they rely on oil between them to form the seal. If it doesn't run for extended periods, it will dry out and leak. It has been a problem since the switch to R-134A. Make sure the compressor runs every couple months and it should be better. Replacing the seal/ compressor wont change things if sitting is the issue.
Cheers
After your help on this I started running my truck with the defroster on. I try to start my truck every week or two to keep things from drying out, but I never thought about the AC compressor. A couple of weeks ago I recharged the Freon and so far I’ve run it with ambient temps between 85-98 degrees and it still blows ice cold. It isn’t loosing pressure at this point. I’ll keep monitoring it, but I think you saved me TONS of money. Thank you VERY much for your feedback. It truly is appreciated. You have no idea how much it means to have the AC working in my L again.
 

L-Bronco

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My pleasure!
I am happy to help, congrats on the win!
I fully understand, it took a couple of weeks to get my A/C recharged after overhauling the engine in my Harley Davidson, (F-150) Amazing how much you miss it!
Cheers
 

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