ethandsmith66
TYF Newbie
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- Jun 9, 2026
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I recently replaced my Evaporator Core (Four Seasons) and Accumulator (GM Genuine OEM 15-10422) on my 03 Yukon XL with 138k. I pulled a solid vacuum on the system before recharging the freon, and it is currently blowing ice cold.
Since the repair, there is a super loud, fluctuating hissing/whistling noise coming from the passenger side firewall/engine bay. It sounds exactly like the pressure equalization hiss you normally hear after you shut the vehicle off, but it is constant the entire time the A/C is running. It fades out slowly after shutdown or when I shut the A/C off.
I did not replace the orifice tube; the original one is still in the line. I unfortunately did not add fresh PAG 46 oil to the new accumulator or evaporator to compensate for what was lost when I threw the old parts away. I sealed the A/C line firewall pass-through with standard foam and tape to build up the barrier between.
I am a bit at a loss on how to proceed. Any ideas or suggestions are greatly appreciated
Since the repair, there is a super loud, fluctuating hissing/whistling noise coming from the passenger side firewall/engine bay. It sounds exactly like the pressure equalization hiss you normally hear after you shut the vehicle off, but it is constant the entire time the A/C is running. It fades out slowly after shutdown or when I shut the A/C off.
I did not replace the orifice tube; the original one is still in the line. I unfortunately did not add fresh PAG 46 oil to the new accumulator or evaporator to compensate for what was lost when I threw the old parts away. I sealed the A/C line firewall pass-through with standard foam and tape to build up the barrier between.
I am a bit at a loss on how to proceed. Any ideas or suggestions are greatly appreciated
