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Hessing sound when pressing on accelerator

rusty813

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When driving my car yesterday, I notice then when pressing on the accelerator, there was a hessing sound coming from the passenger side. What could this be related to? I have a 4wd 4.0l v6 eddie bauer w/40,060 miles.
 


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waskly

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check valve for the ac. should go away when you turn the ac off.
 




rusty813

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the a/c was off when this issue occurred?
 








The Scott

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I have the same issue. Where is this part located?
 








rusty813

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thanks everyone for the help, i will check it out. I was driving long distance today didnt hear anything
 




The Scott

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If this part is bad are any of the systems being degraded? When the part is replaced will the ac work better? thanks for the location info, sounds easy.
 




waskly

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If this part is bad are any of the systems being degraded? When the part is replaced will the ac work better? thanks for the location info, sounds easy.

if its bad, it hisses every time you accelerate. also on small inclines ac cuts out from the vents.
 




Town

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If this part is bad are any of the systems being degraded? When the part is replaced will the ac work better? thanks for the location info, sounds easy.

That check valve maintains the vacuum in the vacuum bottle used to control the vacuum motors in the HVAC. Failure of the check valve will mean the vacuum reservoir will operate at intake manifold vacuum. At idle and other high vacuum conditions the HVAC doors will operate normally. At low vacuum conditions such as acceleration the vacuum will be low and all the doors will revert to their default (no vauum) condition. That will be the defrost position. The A/C will be affected as any other HVAC feature with air going to the windshield.

Replacing the check valve will not change the A/C operation, only the vents from which the cold air will be directed.

Do you have a problem with the A/C not blowing cold air through the dash vents?
 




rusty813

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That check valve maintains the vacuum in the vacuum bottle used to control the vacuum motors in the HVAC. Failure of the check valve will mean the vacuum reservoir will operate at intake manifold vacuum. At idle and other high vacuum conditions the HVAC doors will operate normally. At low vacuum conditions such as acceleration the vacuum will be low and all the doors will revert to their default (no vauum) condition. That will be the defrost position. The A/C will be affected as any other HVAC feature with air going to the windshield.

Replacing the check valve will not change the A/C operation, only the vents from which the cold air will be directed.

Do you have a problem with the A/C not blowing cold air through the dash vents?

mines doesnt do this, just heard a hessing sound when the a/c was off coming from the passenger some place near fuel reset
 




The Scott

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That check valve maintains the vacuum in the vacuum bottle used to control the vacuum motors in the HVAC. Failure of the check valve will mean the vacuum reservoir will operate at intake manifold vacuum. At idle and other high vacuum conditions the HVAC doors will operate normally. At low vacuum conditions such as acceleration the vacuum will be low and all the doors will revert to their default (no vauum) condition. That will be the defrost position. The A/C will be affected as any other HVAC feature with air going to the windshield.

Replacing the check valve will not change the A/C operation, only the vents from which the cold air will be directed.

Do you have a problem with the A/C not blowing cold air through the dash vents?

This is exactly my problem, in addition to the hissing sound. This discussion is much appreciated!
 




dfkimbro

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Thanks for posting this. I think that’s probably the same issue I’m having with my 2010 Sport Trac. Sound like pressure relieving (like opening a beer bottle) when I tap the accelerator.
 




dfkimbro

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Swapped the check valve over the weekend. Issue resolved.
 




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