Compressor knock

[boiler backer]

I have a '92 bonneville with an a/c problem. The a/c clutch went out and I had it replaced. Now there is a nice sounding "knock" in the engine compartment that I am sure is coming from the a/c compressor. This noise was not there before the clutch went out. The clutch engages fine now, and the system cools o.k., but definitely is struggling to keep up with the 95+ degree TN heat. I would like to keep the car for a couple more years.....because it is the best kind of car.....the kind that is already paid for.

Questions:
1) Should I go ahead and have the compressor replaced (quoted at about $1,000)? Am I on the last dying hours of this compressor?
2) What is the noise? Is it the compressor piston? Valves? What?
3) What happens if the compressor locks up? Does it hurt the engine? I saw another post on this site where a guy was selling his car for $400 and said that his comp. locked up and it broke his serpentine belt and started a whole slew of other problems starting with his tranny.

Thx for any help you can offer.

[CDJr]

The knocking started only after this clutch replacement? If its cooling OK, I wouldnt waste a grand replacing it. I would recheck the clutch installation, as it is the obvious problem. Maybe it wasnt installed properly, or the clutch itself is bad. If its from the compressor internally, it should stop when you turn the A/C off. Stand close to it while someone turns the A/C on and off and see if you can pinpoint the source.

[GTP Dad]

It is possible that the clutch clearance is just out of adjustment and causing the knock. However, if the noise starts to get louder get it checked immediately. It would be a lot easier and cheaper to replace the compressor now than to wait for it to go completely out. If you don't want to spend a grand on the replacement go to the local wrecking yard and purchase a used one. Most will give you at least a 30 day warranty. You can probably get one for less than $200. Have it installed and recharged. If the compressor totally fails then it will cost a lot more to replace. Hope this helps!

[boiler backer]

Thanks to both of you for the great advice. The noise definitely goes away when the a/c is turned off, so it must be internal to the compressor. Does this mean that the clutch is not causing the "knock"?

[michael_k0]

Sounds like the compressor and or clutch is bad. Shop around and find a rebuilt one, it's not too hard to install. Be sure to add a couple ounces of refrigerant oil to the new one and take it to a shop and have it evacuated and charged. While its apart put in a new orfice tube and clean the evaporator core if you can. Use new O-rings, they are cheap. If your compressor locks up, you will smoke the belt and lose everything, alternator, power steering, water pump. good luck, mike

[Jim Adams]

shame Boiler Baker,,I have 2 of those compressors on my shelf in the garage ,,if you where qouted that much must be for a new one,,,,is it R134a or R12,,if it is R12 then retrofit it to R134a and giive me a message and I will ship you one out or even if it isnt and you can have it evacuated and keep the R12 I would still get a used one and mine are in A-1 shape,,Im in Delaware,,,I also have a 500 acre junk yard in Jersey for those who need other parts!!! have 5 bonevilles from 92 to 95 all 3.8s