car question -- pulley?

[a mere housewife]

Our car (I lovingly refer to it as our demon donkey) has needed the same major repair every year since we bought it, and this year, three times. It is currently in need of this major repair. What happens is that the air conditioning goes out and then at some later date, after we've patiently sweltered long enough for something else to happen, the belt breaks. The air has gone out again, and presumably it is a matter of time until the belt breaks? I spoke with a mechanic at the dealership today: a surley and overworked but seemingly well informed man who immediately, after I walked outside and found out what make our car is, and relayed this information along with the vague description above, said that it was probably a pulley problem which has gone undiagnosed. This sounds promising, but I would be really grateful if someone like Vic or LawrenceU who not only carry those little 'housewives' and can build planes from scraps of sheet metal but can also fix cars would comment on what exactly a pulley is, how it would be involved, and if it is in fact, a likely culprit. The last repair of the belt was done at a dealership so is under a parts and warranty labor. I'm guessing a pulley problem would not be.

Also the car shakes terribly, especially at low speeds, or when it's not warmed up. Is this related to the above, or just nerves?

---------- Post added at 01:06 PM ---------- Previous post was at 12:41 PM ----------

I should probably mention that our car is a 2004 Mercury Sable. (LS/PE, says our insurance document.)

 

[LawrenceU]

It sounds like you may have a bad A/C clutch.

Sent from my SGH-T959V using Tapatalk

 

[VictorBravo]

Heidi, pulley is a general term.

For background, a pulley is simply a wheel that some thing rolls against, like a belt or even a rope.

In a car, belts ride on pulleys. There are all sorts of pulleys on a belt—they could be “idlers” which don’t drive anything, but instead maintain belt tension. There are power steering pulleys, alternator pulleys, air conditioner pulleys, etc. In most cars they all are spun around by the same belt, but sometimes there is more than one belt.

And the belt is driven by the main pulley, which is hooked to the crankshaft of the engine and spins around and around when the engine is running.

Any pulley on the belt could cause belt wear if it is misaligned (crooked in relation to line of the belt’s travel). Another cause of belt wear is if the thing the belt is driving is seizing up or becoming stiff. Often the problem is a worn alternator or air conditioning compressor.

Also, if the idler pulley I mentioned above is not maintaining the proper tension of the belt, the belt will slip and wear prematurely.

Any of those problems could cause the sound of “belt squeal,” which is an agonizing cry for help that is hard to miss.
And if any of the devices driven by the belt are creating too much drag, that can cause the car’s engine to work harder than it likes. This can show up as excessive shaking at idle speed, or even a car refusing to idle. (There are other causes of this problem too—I should add).

So, that is all background. As you can see, a “pulley problem” can be any number of things. My first guess from the symptoms you are describing is that the pulleys, probably the air conditioner pulley, is out of alignment. That would certainly cause belts to wear out and also cause the air conditioner compressor to prematurely fail.

I wish I could see the beast for myself. It sounds like the mechanic is on the right track, though.

Edit to add: Lawrence's idea is also a likely cause, but, if I recall from your previous issues, you've had this looked at.

Also, if the earlier repair was done without correcting a pulley misalignment, I'd push for it to be under warranty anyway.

 

[a mere housewife]

Thanks very much to both of you. Vic, we wish you could see the beast for yourself also. Lawrence, I'm sure Ruben will read this (I was delegated to ask, but it's okay if I don't understand the answers) and will know if that has been done. I will push for the pulley to be under warranty then. I will try to be very firm about it.

 

[LawrenceU]

Vic is spot on. I posted from my phone in a hurry and was going to come back with the option of mal-alignment. It is more common than people know. One could sort of get away with it with V-drive belts for a while. With serpentine/flat belts it is a definite no go.

 

[PuritanCovenanter]

I agree with all of the above. I find it quite odd that the belt is going bad so fast. That isn't a good thing and is not normal at all. Call my brother in law. I will give you his phone number. Cars is all he does.

 

[a mere housewife]

Thanks very much for the help. I feel much more confident about taking the car to the mechanic who mentioned the pulley -- I am sincerely impressed when any mechanic says something that Vic and LawrenceU also say, and which Randy also endorses.

 

[Edward]

Could also possibly be a bad bearing in the AC compressor. Make sure that the AC is switched off when it quits working. That at least might save the belt if it helps with the vibration at idle.