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What part is this?


New Member
March 1, 2017
Reaction score
City, State
Deeping St James, Lincolnshire
Year, Model & Trim Level
1999 Explorer North face
Belt runs loads of pullys, I have a clattering alternator and at the opposite side under lower down there is a pully with a bit that pops out . . Spins for a bit then pops back and stops but outer pully still moves

Does the same with air con on or off

So what is it and should it do that?

Clattering alternator clatters loads at tick over disappears at higher revs . Think easier just to change it


Grimm G

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Believe you're describing the A/C compressor cycling on and off. It's normal

Are you sure it's the alternator making the noise...and, not the belt tensioner pulley below it? Maybe even the idler pulley.

Thanks for really prompt reply you have put my mind at ease re aircon compressor.

I'm as sure as I can be used the screwdriver to ear trick and sounds as though it's the alternator it is not a constant clatter but only pauses for maybe two to three seconds at low revs then clatters for a second or two

Update... (cant access on phone due to security certificate)

Removed belt, ran car.... no other noises.

Replaced belt and noise back, a full time clatter at below 1200rpm.

Again used screwdriver to ear and on alternator and sure its that, however the pully below which is the tensioner pully does have back to front slight movement. So could be this, is there any quick fixes or temp fixes to eliminate the pully or alternator?

I judge the condition of my pulley bearings by spinning and wiggling them by hand. If they feel dry, make any noise, wiggle and don't spin as smooth as silk they should to be replaced.

I just replaced both the idler pulleys, the tensioner pulley and A/C clutch on our 2000 Mountaineer 5.0L AWD. They all needed to be replaced (espically the A/C clutch), but I still have a rumbling noise, especially when the engine is cold, along with a sometimes squeak (which is not the cam synchronizer) so next will be the damn water pump. I can feel a little play in the w/p bearing and I can see a slight wobble in the w/p pulley when the engine is running, plus it's the only thing left. I'm trying to get my mechanic buddy to replace the w/p, as I've done this job on my other 2000 Mountaineer and don't want to do it again. Unfortunately he's really busy right now, so I may get stuck tackling this job again (I really hope not). He's quoted me $125 labor to replace the w/p. That's worth every penny and more. I'd have no problem paying him $200 to do this miserable job.