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  #1  
Old 10-31-2015, 04:35 PM
jrobinson004 jrobinson004 is offline
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Posts: 8
Default Possible Vacuum Leak

I have a 1998 Ranger 4.0 (OHV)

I hear a hissing sound when I accelerate ...
-Similar sound to air coming out of a tire
-Seems to be coming from somewhere near the gas pedal (not sure which side of the firewall
-It definitely gets louder as I accelerate more and makes no sound when idling
-I am not sure if the issues are related, but the truck also seems to be running a little on the hot side

Other than the noise, the truck seems to be running fine (no hesitation or rough idling).

Any thoughts?

Thank you,

-Justin
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  #2  
Old 11-01-2015, 06:52 AM
musclecarman2 musclecarman2 is offline
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Default Re: Possible Vacuum Leak

Have you checked your antifreeze level?. If it's running hotter you may have a leak in the system. (heater core, hoses etc.) look for fluid on your carpet or under the truck. Just a thought.
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  #3  
Old 11-02-2015, 02:29 PM
modelageek modelageek is offline
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Join Date: Jan 2009
Posts: 6,268
Default Re: Possible Vacuum Leak

Quote:
Originally Posted by jrobinson004 View Post
I have a 1998 Ranger 4.0 (OHV)

I hear a hissing sound when I accelerate ...
-Similar sound to air coming out of a tire
-Seems to be coming from somewhere near the gas pedal (not sure which side of the firewall
-It definitely gets louder as I accelerate more and makes no sound when idling
-I am not sure if the issues are related, but the truck also seems to be running a little on the hot side

Other than the noise, the truck seems to be running fine (no hesitation or rough idling).

Any thoughts?

Thank you,

-Justin
Check for codes! If it's a vacuum leak you'll have a code.

Also the IAC valve has been know to whistle when it is failing.
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2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).
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  #4  
Old 11-02-2015, 04:57 PM
barneycat11 barneycat11 is offline
2006 FX4
 
Join Date: Nov 2014
Posts: 390
Default Re: Possible Vacuum Leak

Check the vacuum line to the brake booster.
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  #5  
Old 11-05-2015, 11:49 PM
jrobinson004 jrobinson004 is offline
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Default Re: Possible Vacuum Leak

Anti-freeze was low, maybe 1/3 of a gallon. I refilled the coolant system (checked the oil, which was good) and went back out. The hissing sound continued even when the truck was cool (immediately after pulling out of the driveway).

If it is the brake booster line - would driving the truck cause any further damage?
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  #6  
Old 11-06-2015, 10:58 AM
barneycat11 barneycat11 is offline
2006 FX4
 
Join Date: Nov 2014
Posts: 390
Default Re: Possible Vacuum Leak

Check the hose plastic fitting at the booster and the connection on the motor for a leak.The leak won't hurt anything but might make the motor run rough and affect performance and fuel mpg.
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  #7  
Old 11-08-2015, 05:02 PM
jrobinson004 jrobinson004 is offline
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Default Re: Possible Vacuum Leak

I think I found the culprit ... I assume the EGR pressure sensor is supposed to have vacuum hoses connected to it? Both of the fittings are missing hoses.

Am I also correct to assume that each connects to a fitting in the exhaust manifold (as that seems to have two similar fittings, also without hoses connected)?

Sounds like a cheap fix ... hopefully.
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  #8  
Old 01-02-2016, 01:54 PM
jrobinson004 jrobinson004 is offline
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Default Re: Possible Vacuum Leak

An update ...

I replace the hoses connecting the EGR pressure sensor to the exhaust and no more hissing sound. However, now my truck has no power (especially in the low end and mid range). It feels as though I am towing something.

The transmission is fine, but power has decreased - gas mileage has also gone down about 20%.

Could the EGR sensor be bad?

Thank you,

Justin
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4.0 ohv, hissing, leak, vacuum

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