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Expansion Valve Leaking?

GovtMule66
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GovtMule66 Enthusiast

GovtMule66

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My Dad owns a 2015 GMC Sierra 1500 Denali with the 5.3 engine package. A few back he noticed the truck wasn't cooling like it should and after checking the low & high side pressures decided to add a small amount of freon. When I say small I mean small because all it took to get the truck acting right again was about 5-6 oz of freon. Fast forward 2 weeks and now he is back in the same boat again and has began the process of tracking down the leak. The first place I looked was the AC Condenser but luckily his hasn't broke at the top corner like many others have experienced. Today I had my HVAC freon checker/sniffer out going over the truck and every time I passed over the left side of expansion valve it went off. Does anyone know if these Expansion Valves are known to leak here? The freon checker didn't go off when I passed over the o-rings where the cooling lines connect, it would only go off when I passed over the left side.

Thanks in advance for any help you can give.

 

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Snowcamo Senior Enthusiast

Snowcamo

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Posted

When the system does not have pressure, unfortunately the expansion valve. It has two o rings.  Replace them.  You can use a heavy mix of soap and water to verify the leak. If bubbles are present with the system pressurized, then well.....

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GovtMule66 Enthusiast

GovtMule66

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6 hours ago, Snowcamo said:

When the system does not have pressure, unfortunately the expansion valve. It has two o rings.  Replace them.  You can use a heavy mix of soap and water to verify the leak. If bubbles are present with the system pressurized, then well.....

I followed your advice which I appreciate but now I have another question.  As you can see in the photo below when we sprayed the soapy water on the expansion valve bubbles appear.  If I turn off the AC off but leave the fan running bubbles appear.  If I turn my fan & AC completely off the bubbles stop which I don't understand.  The AC system in our truck is currently charged and working properly.  Why would the bubbles stop the minute I cut the fan off if the expansion valve is leaking especially in a pressurized system? Is there any chance the air coming off the evaporator blower is passing by the expansion valve causing these bubbles?  I guess if I put UV Dye in it would answer my question but I thought I would throw this out there.  With the amount of bubbles I was seeing I wouldn't think a system would hold freon more then a day where this one is lasting about 2 weeks. 

 

Once again thanks for the help

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txab Senior Enthusiast

txab

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If it only leaks while fan is running but not when compressor is running sounds like  a simple plenum leak, not refrigerant

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GovtMule66 Enthusiast

GovtMule66

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13 hours ago, txab said:

If it only leaks while fan is running but not when compressor is running sounds like  a simple plenum leak, not refrigerant

The bubbles are present if I spray soapy water around the expansion valve then turn on the AC on.  The bubbles are also present if I spray soapy water around the expansion valve and just turn the fan on by itself.  The minute I turn the AC & Fan both off the bubbles stop.  Maybe I'm wrong but I would think there should be bubbles all the time if the expansion valve is actually leaking.

 

Thank you for offering to help us.

Edited by GovtMule66
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txab Senior Enthusiast

txab

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I would think so too. It would appear to be an air leak. There has to be some kind of seal or sealant where the X-valve penetrates the firewall

  • 1 year later...
GovtMule66 Enthusiast

GovtMule66

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On 9/22/2025 at 9:25 AM, phatrabbitzz said:

@GovtMule66did you ever figure this out? 

My Dad ended up having to replace the A/C Compressor along with the A/C Condenser which cracked in the same spot as other GM owners.  Since we had the entire A/C unit basically torn apart we went ahead and replaced the expansion valve as well.  I'm sorry I don't have a better answer for you. 

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