2003 Ford F150 Engine noise / squeek

Hi mattaylor81,

I guess it is just a squeaky belt. Check the compressor belt tension, shoud need some adjustment or replacement of the belt.

[quote:3900600628="mattaylor81"]Noises problem
2003 Ford F150 V8 Four Wheel Drive Automatic 66000 miles
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Recently had my knock sensor replaced a week and a half ago and everything had been working fine. Was driving around yesterday and turned on my A/C for the first time this year. After about 1 minute of my A/C working I started to hear a slight, rapid, ticking coming from my engine compartment. Then I also realized that when I would accelerate to pass on the interstate it would downshift to accelerate but whenever it would shift back into overdrive it would make a squealing noise identical to what a bad belt sounds like. At first I thought it may have been related to all of the maintenance involved in changing the knock sensor until I realized it coincided with me using the A/C and the squeaky belt sound. I don't know if possibly my A/C compressor is bad or not. Thanks in advance for the help.[/quote:3900600628]

The first thing I would check is the Tensioner pulley and the Idler Pulley. Turning on the A/C will put a little extra pressure on the belt.

To check the pullies 1st with engine off spray the center bolt on ONE of the pullies with WD40 or similar, then start vehicle. If squeal goes away replace pulley, if squeal still there repeat proceedure with other pulley.