Engine 2000 GT 4.6 V8 Noise coming from Pulleys... how to (pic attached)

Discussion in 'SN95 4.6L Mustang Tech' started by Sams2000GT, Apr 5, 2013.

  1. Hi guys,

    My engine (123K miles) has had a small whine over the last few months, nothing too bad but definitely noticeable. It was more prevalent during cold winter days. Last week I was driving it and the noise started to get a lot worse to the point where I heard a metal on metal scraping noise. I immediately pulled over and checked the engine. I narrowed it down to a bad pulley. I drove it back home and it has been in the garage since.

    Once home, I released tension on the belt using a ratchet on the belt tensioner and spun all the pulleys. The two pulleys that make noise are the two circled in red on the attached image.

    The bottom one is really loose and make a lot of noise when spun while the one on the top is noisy but nothing like the lower one.

    Are these both referred to as the idler pulleys? I did some research and came up with Motorcraft Part #'s YS249 (lower ribbed pulley) and YS245 (smooth upper pulley). Should they be replaced with Motorcraft or is there a better brand out there?

    Lastly, is this an easy repair? The smooth upper idler pulley looks very easy to replace. The ribbed lower pulley looks more difficult (it has a AC line dryer in front of it) and I have researched this problem and have seen people mention that this one is reverse threaded. What exactly does that mean?

    I am not super technical but I have done some repairs to the car. Does this require a mechanic or is this something pretty easy to get done?

    Thanks in advance for your help!

    P.S. attached image isn't my car, just found it on the web and put circles on the problem areas.

    Attached Files:

  2. Thanks for the reply trinity_gt. Are either of these reversed threaded? And do I have to worry about the correct torque applied? I don't have a torque wrench. Also before I remove the belt is there a belt diagram better than the one on the underside of the hood?

    Hopefully it isn't too much of an issue to replace these. I am just hoping that the lower idler pulley isn't an issue with that AC filter dryer in the way.
  3. a) No, neither is left-hand thread.
    b) Torque isn't critical. Just do them "goodntight." Go back and check them after a hundred miles if you're worried. It's about 18 ft-lbs so think how you'd tighten a spark plug and just do that.
    c) You can use this for reference:
    d) The nut holding the bracket for the dryer can be remove and the dryer bent slightly out of the way for clearance without issue.

    Attached Files:

    Sams2000GT and Kilgore Trout like this.
  4. Thanks again trinity_gt for all your help! Replaced both pulleys today and the car sounds much better. Everything is working as expected.

    Attached Files:

  5. My car was making a loud screeching noise caused by the belt/belt tensioner.

    The old tensioner for some reason was making the belt move out of place and the belt was hitting the engine and rubbing against it. I put in a new tensioner and changed the smooth idler pulley above it also and it runs fine without the noise anymore.