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Real squeaky a/c pully

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  • Real squeaky a/c pully

    '11 Crown Vic 4.6 here and it seems I've got a real squeaky a/c compressor pulley. I don't have a lot of experience with this car but the noise changes noticeably when the comp clutch kicks in and out, and a close listen seems to locate the sound right at that pulley. The sound is always there whether the a/c def is on or not.

    What needs to be replaced? The entire clutch assembly, or possibly just the pulley?

  • #2
    Are you sure it's not the idler or tensioner pulley? They are easier and cheaper to replace and they do wear out often. You can spray each at the bearing with penetrating oil one at a time then start the engine to see if the noise changes then.

    1994 Deep Jewel Green 183,142 miles
    1997 White LSC 135k miles
    1998 White Collectors Edition 175k
    1994 Black (#2) 100k miles
    1993 Deep Jewel Green Convertible


    • #3
      I took your advice and got some PB Blaster in each of the other two pulley bearings and the sound didn't change a wink. When I was diagnosing it earlier I used a thick piece of cardboard to block the sound coming from each of the pullies one at a time and that pretty much isolated the sound as coming from the compressor. Now after this last test I'm sure that's where the problem is.

      Any advice on how to approach this further?

      From the videos I've seen it looks like I'm gonna have to take the vehicle to a shop to get the R 12/13 ? evacuated and refilled after everything is back together as this apparently requires taking the compressor completely off.
      Last edited by bradhays; 02-07-2019, 05:02 AM.


      • #4
        If it's just the clutch bearing, I know that can usually be replaced separately from the compressor, so you don't have to open the system. It's usually not much more money to get a whole new compressor (with clutch) however. For what it is worth, yours will take the R134a refrigerant which is readily available. (although still illegal to discharge to atmosphere, if I recall) Even if a Shop does this whole job for you, I don't think it should be all too expensive.

        Although it's possible that both the compressor /and/ the clutch are noisy, it will usually be one or the other. (is it quiet when the AC is running? then it's just the clutch bearing!)

        If you don't already own one, a cheap automotive stethoscope is great for tracking stuff like this down. ( You can put the "stick" on the component in question, and you'll know for sure.

        Bill is right in that the idler/tensioner pullies are a common failure point, but they're also dirt cheap, and easy to replace. So it's really the failure you'd prefer to have..

        Alternatively, if A/C is not a priority for you, there's a few ways you can simply bypass it by getting a shorter belt, and routing things a bit differently.
        Mike Martin

        1997 Mark VIII LSC 5.0
        2001 Dodge Dakota


        • #5
          Thanks for the help guys but contrary to what I was thinking this one actually turned out to be the serpentine belt...and it sounded so much like rotating metal on metal. I was really sure the sound was coming directly from the compressor pulley area, but I guess even when it's the belt it's gonna be squeaking at a certain stress point, which would be a pulley.

          So glad I changed out the belt before I got into anything else. At least I learned a lot about working on compressor components.

          Now on to the spark plug that blew out this weekend. In the number 4 position too so its not easy to get back to. I'll start another thread for that one though.


          • #6
            What makes a belt squeak like that anyway? I guess something that gets on it? Is there any way to clean it so the squeaking stops? Belt looks fine and not a single crack in it. Or can the squeak be caused by an internal breakdown in the belt somewhere?


            • #7
              Belts have been squeaking ever since... there were belts!

              Back in the old days it was common to spray belt dressing on v-belts as they had a tendency to glaze over and start slipping with the tell-tale squeak under load.

              Modern serpentine belts do not require such dressings and as a general rule they are required to be clean and free from any foreign material. Often in the service manuals, there will be warnings of the need to fully rinse with clean water and clean the belt and pulleys should any antifreeze contamination occur. Of course, common sense says not to get any oil or grease on belts and pulleys as well.

              Besides contamination, mechanical wear or misalignment will cause belt issues, including squeaky belts. Often the pivot of the tensioner will wear causing the tensioner arm and pulley to be out of alignment with the fixed pulleys. This will put a tangential load on the rotating belt which will build until it 'slips' resulting in a squeaky belt.

              Most quality belts have design features to minimize common issues associated with slipping under load but often there can be oscillating loads that will stress the belt over time causing structural damage to the belt that may or may not be visible. But as a general rule, serpentine belts will last a long time with proper observation of wear and condition. Like many other maintenance issues, short belt life is a simply a symptom of a larger concern.