2000 Ford Mustang Whistling noise

Tiny
LADY G
  • MEMBER
  • 2000 FORD MUSTANG
  • 3.8L
  • V6
  • AUTOMATIC
  • 200,000 MILES
Car makes a whistling noise after vehicle is turned off. This happens about 2 to 3 seconds after turning off the engine. Sometimes it's a very short whistling noise or it could last about 6 to 10 seconds. Is this a major issue? How can it be stopped?
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Wednesday, May 27th, 2015 AT 2:38 PM

4 Replies

Tiny
SUPPUSH
  • MEMBER
If it only happens with the air conditioning running at the time you turn the vehicle off its the pressure balancing between the high and low side through the orifice/expansion valve. I'm a hvac guy not a mechanic though. But if your running 134a there is about a 200 psi difference on the system when it all turns off. It will almost sound like water running through a pipe
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Wednesday, May 27th, 2015 AT 7:08 PM
Tiny
CJ MEDEVAC
  • EXPERT
IF YOU HAVE BEEN RUNNING THE A/C OR ANY HEAT SETTING WHICH USES "DEFROST", THE COMPRESSOR PUMPS THE FREON (LET'S SAY HALF) PART OF THE SYSTEM TO (LETS SAY 100 PSI)

THE OTHER "HALF" IS UNDER SUCTION AS THE COMPRESSOR IS PULLING THE FREON BACK AROUND TO BE PUMPED UP AGAIN

SORRY, SIMPLE TERMS SEEM TO BE UNDERSTOOD BETTER!

THE REASON THE COMPRESSOR CAN BUILD UP THE 100 PSI IS BECAUSE THERE ARE "ON PURPOSE" RESTRICTIONS IN THE SYSTEM (LIKE AN ORIFICE TUBE, OR AN EXPANSION VALVE) WHICH "DAMS UP" THE FREON FLOW

IT'S DESIGNED LIKE THIS SO THAT LIQUID FREON TURNS TO GAS AND AFTER THE GAS GATHERS THE HEAT FROM THE COCKPIT, IT TURNS BACK TO LIQUID

(A YOU TUBE VIDEO ON "AIR CONDITIONING" (AN ANIMATED ONE MIGHT BE BETTER!) MIGHT SHOW YOU THE WAY IT ALL WORKS

BUT BACK TO THE MEAT AND POTATOES

WHEN YOU SHUT THE A/C / CAR OFF

AGAIN, FOR SIMPLICITY'S SAKE, HALF OF THE SYSTEM IS AT 100 PSI AND THE OTHER HALF IS AT -10 PSI, THE SYSTEM EQUALIZES, TO THE SAME PSI THROUGHOUT.

BEINGS THAT THE "RESTRICTIONS" ARE IN THE SYSTEM, THE FREON "WHISTLES" THROUGH THEM SO THAT IT CAN BE EQUAL PRESSURE IN THE "OFF" A/C SYSTEM

POP THE HOOD NEXT TIME, HAVE SOMEONE SHUT OFF THE CAR, LISTEN AND LOOK TO SEE IF THE NOISE IS GENERATING FROM THE A/C COMPONENTS

LEMME KNOW IF THIS IS THE "CAR MONSTER" YOU ARE EXPERIENCING!

MY "A/C" WHISTLING VARIES AT DIFFERENT SPEEDS AND STOPS EVERY TIME MY JEEP STOPS, SEE PICS BELOW

THE MEDIC
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Wednesday, May 27th, 2015 AT 7:28 PM
Tiny
LADY G
  • MEMBER
Hi Suppush,

The whistling noise actually occurs both when the a/c is on or not, when the engine is turned off.
Thanks for your response.
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Wednesday, May 27th, 2015 AT 9:42 PM
Tiny
CJ MEDEVAC
  • EXPERT
WHAT ABOUT THE POSSIBILITY OF THE VACUUM RESERVOIR EQUALIZING OUT?

I COULD NOT FIND A DIAGRAM OF/ IF YOURS HAS ONE

USED TO BE THEY LOOKED LIKE A LABEL-LESS BLUEBIRD ORANGE JUICE CAN (OR A QUART SIZE SOUP CAN) WITH A 1/4" HOSE, OR SO, ATTACHED TO THE CENTER OF ONE END. OTHERS LOOK LIKE A BLACK BASEBALL MOUNTED ON BRACKETS. USUALLY FOUND UNDER THE HOOD ON A FENDER OR THE FIREWALL

FOR LACK OF A BETTER EXPLANATION, IT STORES VACUUM, IF/ WHEN VACUUM LACKS, DUE TO PULLING A HILL OR FLOORING IT, YOUR "VACUUM OPERATED STUFF" WILL NOT SUFFER. MANY TIMES VACUUM WAS USED INSTEAD OF 'LECTRIC MOTORS, SUCH AS ON HVAC DOORS INSIDE THE HEATER BOX. WITHOUT THE RESERVOIR THEY MIGHT OPENING OR CLOSING WHEN THEY SHOULD BE A-STAYIN' IN A CERTAIN POSITION THE WHOLE TIME.

THE MEDIC
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Thursday, May 28th, 2015 AT 4:24 PM

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