First off, let me say this -- it sucks bigtime.

Earlier this summer, my refrigerant ran out due to a slow leak. I let it be over the last few months and just recently decided to fix it. I took it to the local Cadillac dealer to refill and fix the leak, but unfortunately, the compressor was now making lots of noise (oddly, it was still working fine, but just making a lot of noise when engaged). The dealer quoted me a price of $1200 to replace the AC compressor. Of course, their prices tend to run about 4x what you can do things yourself for, so here are my experiences, for what it's worth:

At O'Reilly, a new compressor was about $310, with remanufactured being $210. Core was $10. Other things you will need or expenses you may incur if undertaking this project:

AC pressure guage set: ~$80
AC oil and R134a: ~$50
Extra refrigerant can valve: ~$8
8 quarts of oil and a new oil filter: ~$?
Air compressor capable of maintaining roughly 90PSI with constant drain: ~$?
Air compressor powered vacuum (i.e. Air-Vac): ~$?
R134a recycling / system depressurization at repair shop, if system is pressurized when you start: ~$?
Ratchets, wrenches, some of those ratcheting wrenches, and a rediculous combination of extensions and universal joints: ~$?
Small hands: Priceless

Some specifics:

Best as I can tell, the high viscosity PAG 150 oil should be used with GM A/C systems, including the Cadillac. The guy at O'Reilly had a big chart that said a 97 Seville holds 8 ounces of oil and about 32 ounces of R134a. Of course, some of that oil comes out with the compressor when you replace it, and some of it stays in the system, so figuring out how much to put back in, as well as where to put it, is a difficult task. Getting the compressor out will most likely require removing the oil filter, so might as well do an oil change at the same time, thus the oil and filter requirements shown above.

The Steps:

1) If system is still pressurized, get system R134a recycled and system depressurized at a repair shop. For free, you could just vent it into the atmosphere, but doing so is bad for the environment and can result in a hefty fine if the EPA happens to drive by while you are doing it.
2) Drain oil and remove oil filter.
3) Jack up car and put right front side on jack stands.
4) Remove right front wheel.
5) Remove wheel well covers on the front side (2 pieces). This will provide access to the front of the compressor.
6) It may be helpful to also remove one or more of the covers on the bottom of the car for better compressor access.
7) Release the serpentine belt. There is a spring loaded idler pulley that is best turned using a half inch breaker bar. There is a square hole in the side of the pulley that I think is designed for this purpose.
8) You could do this sooner, but unhook the battery ground terminal.
9) Take all the mounting bolts out -- there are 2 main bolts and 1 main nut on the front side that are easy to get to. Then there are 2 smaller bolts on the back (there is also 1 large bolt on the back, but it's not a mounting bold -- it's used to hold the AC lines onto the compressor). One of the smaller bolts is easy to get to, the other is quite difficult to get to (one of those ratcheting wrench combos will work well for this one). You should now be able to move the compressor forward a bit, which will help give you extra room as needed to accomplish the remaining tasks.
10) Un-plug the electrical connection to the compressor. It's towards the front of the compressor, and facing the front of the car. It couldn't be placed in a much worse position. You can't see it and manipulate it at the same time, so good luck with it. Easiest way to get to it is through the wheel well.
11) Unbolt the AC line mounting bolt from the back of the compressor. This bolt sucks. Here is where some creativity and a lot of extensions and universal joints will come in handy. You might be able to just barely grip and turn it with a regular wrench, but it won't be fun.
12) You can now pull the compressor out through the wheel well. This is also a good time to curse about how you will never buy another Cadillac.
13) Take a break and let the anger fade.
14) Good luck figuring out how much oil to put in the new compressor. Follow the directions your replacement compressor came with as needed. Mine told me to put half the oil in the "suction" side of the compressor, and the other half in the low pressure line. Why? I dont' know. That's just what it said. How much oil? Another good question. I don't know. Something I've seen repeatedly is to replace as much as came out with the old compressor. How do you tell how much is in the old compressor? Another good question I can't answer. I played the guessing game and decided to put roughly 3 ounces into the suction side of the compressor before installing it, and another 2 ounces in the low pressure line using one of those 2-ounce pressurized oil cans when charging the system later. I don't recommend playing guessing games, but information is very sketchy. Could use some real mechanics with experience to help out on this one.
15) Replacing the compressor is basically the reverse of removing the old one. Make sure you start by putting the new seals in. There is a seal between the compressor and each of the two AC lines going into the compressor (2 seals total). The seals slide nicely onto the AC lines, so at least you won't have to juggle holding them in place when installing the new compressor. Books may tell you to use certain torque specifications. Normally this is good advice, but there is no way you will be able to use a torque wrench on all the bolts, so on some you will just be guessing.
16) Hook up your guages and use your vaccuum to vacuum out the system. This gets all the air out and helps remove moisture (both bad things to have in your AC system). After running the vaccuum for awhile, shut off the valves, turn off the vaccuum, and let it sit for awhile to see if it loses it's vaccuum. This is a nice way to check for leaks before pressurizing the system.
17) Unhook the connector from the AC pressure sensor and jump the two wires together. It's not easy to explain in words where the sensor is, so I'm not going to try. I'll add a picture later if someone needs it and I still own the car. Jumping the wires will keep the system from shutting off the compressor due to low pressure when you first start filling the system. Make sure you are using the right wires...jumping the wrong wires on the wrong connector could cause bad things to happen.
18) Hook the battery back up.
19) Oops...don't forget, put the new oil filter on and top off the oil if you haven't already.
20) Make sure all tools and hoses are clear of the engine. Start car, turn on AC at max, and charge the system. Follow the instructions your guage set came with. You should be filling only through the low pressure side, though you can watch the pressure on both sides if you have a full guage set. It should take roughly 32 ounces or maybe a little less...that's about 2.5 normal sized R134a 12oz cans. Do your best to keep regular air out of the system when switching cans. When full, the temperature of the air coming out of the vents should be about 30 to 35 degrees less than the ambient air temperature. You can buy air temperature gauges for this purpose. If I remember correctly, the low pressure side will be holding at around 35 to 40 pounds.
21) Be very mindful of your valves when charging. One mindless mistake could result in a rapid and potentially dangerous decompression. Plus you may have to buy more refrigerant and start the charging process over from scratch.

Hopefully at this point, everything works, and you can rejoice.

 

Another quick note. AC oil is VERY VERY SLIPPERY!! Be careful if you spill any. Even after you think you have wiped it up good, the concrete will still be somewhat slippery. So be careful.

 

nice write up.

let me add that the OIL also leaks our when the refrigerant leaks out
and often the compressors fail due to running w/o oil unless the car has a
auto-shutt off for low refrigerant.

i hope #12 & #13 fade away.
remember, these cars were not designed for the do-it-yourself.
there are much worse things to maintain out there than Cadillacs .

thanks for the write up.

 

Very good Skotty, just did the same job on my wife's Suburban. You will be somewhat displeasured to hear that the compressor changes in 4 minutes, no...probably 3 minutes. It sits right on top of the motor, 5 bolts, loosen belt as you describe and its in your hand.

 

I was only joking about #12 and #13. Might I also reiterate that I am not an expert. I do have a lot of experience working on cars in general, but I don't work on AC systems too often, and this is the first time I have worked on the AC system of a Cadillac. Thus, use this write-up as a companion rather than a how-to guide. Just sharing my experience to contribute to the collective knowledge base.

I'm happy to hear the Suburban only took a few minutes. I would never wish a hard repair on anyone. Oh how aggravating it can be to spend 30 minutes on one difficult to reach bolt or nut!

 

I'm doing this same thing on my mother's 1998 Cadillac Deville since she couldn't afford paying $1,200.00 for a shop to do the job.I myself am not a mechanic however I do know my way around under the hood, now with this said I'm having a hell of a time with the oil cooler line's above the oil filter adapter and bolt on bracket! Is there a secret trick or something to remove these last few things? Please anyone that has helpful info don't be shy by no means...