Hissing sound
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From: Sioux City
Hissing sound
*I'm new to these forums.*
2000 XLT 4.0 4x4
My 2000 4.0 4x4 makes a hissing sound in the engine bay back towards the cab. The question I have is: What could have caused the truck to hiss like that? I'm thinking it is a vacuum leak.
If it is a vacuum leak, is my gas mileage going to fluctuate, or is it a simple repair?
It runs fine, no issues in steering or powertrain.
I await some feedback. Thanks in advance!
2000 XLT 4.0 4x4
My 2000 4.0 4x4 makes a hissing sound in the engine bay back towards the cab. The question I have is: What could have caused the truck to hiss like that? I'm thinking it is a vacuum leak.
If it is a vacuum leak, is my gas mileage going to fluctuate, or is it a simple repair?
It runs fine, no issues in steering or powertrain.
I await some feedback. Thanks in advance!
Welcome to the forum
Check the vent cap on the IAC Valve, pictures here: How to: - IAC valve cleaning thread (w/pics) | Ford Explorer and Ford Ranger Forums - Serious Explorations
It's the black cap, it can make a whistling noise
Vacuum leak test
After engine is fully warmed up and idling
Open the hood and unplug the 2 wires on the IAC Valve
Idle should drop as IAC Valve closes
Should drop to 500rpm or engine may even die, either is GOOD, it means no vacuum leaks
If idle stays at 700 or higher then there is a leak
There is a Cam Position sensor and Synchro tower at the back top of the engine, the bushings in the synchro tower can wear out, but that noise is usually described as "squealing"
If you get yourself a 4ft length of rubber vacuum hose it works great as a stethoscope to isolate where a noise is coming from
Check the vent cap on the IAC Valve, pictures here: How to: - IAC valve cleaning thread (w/pics) | Ford Explorer and Ford Ranger Forums - Serious Explorations
It's the black cap, it can make a whistling noise
Vacuum leak test
After engine is fully warmed up and idling
Open the hood and unplug the 2 wires on the IAC Valve
Idle should drop as IAC Valve closes
Should drop to 500rpm or engine may even die, either is GOOD, it means no vacuum leaks
If idle stays at 700 or higher then there is a leak
There is a Cam Position sensor and Synchro tower at the back top of the engine, the bushings in the synchro tower can wear out, but that noise is usually described as "squealing"
If you get yourself a 4ft length of rubber vacuum hose it works great as a stethoscope to isolate where a noise is coming from
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bradshaw75
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Feb 23, 2010 04:12 PM
