04 Lesabre - Strange Grinding Noise On Acceleration

My 2004 LeSabre has developed a problem that also occured on my previous 2000 LeSabre in its old age. Unfortunately after numerous trips to the dealer, the problem was never solved on either car. With the A/C turned on under hot driving conditions after the engine has come up to temperature the problem will occur frequently. Essentially when I accelerate I can hear a loud grinding sound under the hood on the passenger side. The noise will abruptly cut in and out as the engine revs up. You hear it in pulses as the engine revs up to redline. It is especially loud under very heavy acceration from a dead stop. When the A/C is switched off all of the noise goes away and I hear nothing unusual. The dealer installed a brand new compressor and it didn't solve the problem. It almost sounds as though two pieces of metal are vibrating together. Although the dealer insists the problem would have to be the compressor, I tried to argue that the normal vibration caused by the compressor working could be triggering some other component in the loop to vibrate. Unfortunately I can't replicate the problem with the car standing still. It simply doesn't make the noise unless the engine is under heavy load at high rpm's. I would describe the noise as something that sounds like a coffee grinder.

I finally got my car to make the noise with the dealer tech in the vehicle. He noted that he would have never heard it since he "doesn't ever drive that hard." Lol... I had to explain that I don't always go around pounding the pedal to the floor off every light unless I'm trying to duplicate a problem. I'm scheduled in for friday again where he claims he will apply some different techniques to try and pin down the source of the noise. I really don't have the time anymore to work on the 04, between work and school I'm constantly crunched for time. I'm going to try to remember to post the solution if we get it figured out. Sometimes I end up solving issues long after I've posted something in the forum.

The car is also going to have its windshield replaced for the second time in two weeks because the PPG window they installed seems to have distorted my head up disply. Hopefully the next attempt will work out better with a different brand of windshield. It seems you can't ever get anything done right the first time now days.

The A/C compressor clutch should totally disengage at WOT (to protect the compressor) & re-engage at part throttle. This is controlled by the PCM. I am wondering if the clutch plate has enough clearance to totally disengage; if not, it may be dragging and high rpm centrifugal force keeps it partially engaged, hence the clanging sound. BION, I have seen this happen!

I know you said you replaced the compressor, but I had the same problem as you, and it was the compressor. After the replacement the noise went away.

I do have a scan tool set up on my laptop that allows me to watch the A/C clutch commanded state. The noise occurs between 70 and 85% throttle. I configured the scan tool to read out throttle angle, engine torque, A/C clutch state, and engine speed. The suggestion about the A/C clutch partially disengaging was excellent and that's exactly why I hooked up my scan software last week. I figured the noise was occuring at high rpms at WOT when the computer commanded A/C off. Unfortunately its not, the A/C should be fully engaged when I'm hearing the noise. Unless the clutch mechanism is fail safe so that it must be "held on" which could mean it is partially slipping under those conditions. Once you hear the loud noise condition you can actually hear some grinding noise all the time under all driving conditions with the A/C on. More than the usual compressor noise, in my opinion. I really think the compressor is junk, even though I know it is a brand new delco part installed by the dealer. Perhaps their quality is headed down hill, in my experience AC Delco OEM parts are usually quite good.

ACDelco, (like everyone else), is outsourcing to low wage/no benefit countries, such as Mexico, India & China. Do you know for sure that the compressor was a new one, or was it rebuilt? Did they change the orifice screen (expansion valve) & accumulator when the compressor was installed? Check line pressures @ idle & higher rpm!

Yeah I believe the days of trusting AC Delco parts at face value are over.

However, good suggestion Bo! As we all know the Harrison V5 compressor is a variable displacement compressor meaning its operation will vary with engine load and other conditions. It is always engaged unless you go to WOT, etc.

Is this sound an actual grinding noise or a moaning sound that varies? V5 compressors will motorboat when the charge is below what it should be and depending on temperature and humidity conditions even though cooling may feel satisfactory. Anyways the compressor appears to be the most likely suspect since the noise is gone with A/C off and it doesn't sound like the clutch bearings.

Yes a/c compressor shuts off at WOT.. and this could be the resulting scrapping noise- easiest way to test is to listen with a/c off at idle as well.

You all want some detail on V-5 compressor clutch dragging noise?

With all due respect to you did we ask for any? Most us that give automotive HVAC advice are aware of the operation so we do not need any lectures in that regard. Plus most of us go by what the OP has posted and any replies that seem reasonable whether you agree with them or not. He never mentioned anything about any clutch noise at idle and this problem shows during some form of acceleration. Also, he emphasized the noise was a grinding sound not rattling which is the noise you get when the clutch air gap is off, i.e. between the clutch plate and pulley. Also, if the air gap is off the noise will be there with the A/C off and compressor disengaged at least in my experiences.

Okay let me jump in here and provide some updates. First of all I picked up the vehicle Friday from the dealer. They decided to go ahead and replace the compressor again. It changed nothing, the sound is identical, no change, same conditions etc. Now I'm starting to think this may not be the compressor. The noise still immediately disappears when the compressor gets shut off though. Tomorrow afternoon I plan to touch up a couple of things. First of all the heater outlet tubes near the bottom of the alternator appear to have some play in them, I'm going to get some lock washers and tighten them up. Also, there is a simple metal clip that clips the windshield washer line against the firewall. The heater hoses rub against the washer line, and the clip is loose. I'm going to make sure that gets tightened down with a nut as well. Just to be sure this isn't something really silly, I want to trace through all the A/C plumbing and make sure there is nothing making contact against a metal part, particularly when the engine flexes in its mounts on hard acceleration. I also want to make sure all of the brackets and hardware on the belt loop are tight.

I spoke with the technician at the dealer because my primary concern is that the compressor is not properly oiled internally. He assured me that he measures the amount of oil lost from the old compressor and replaces an equal amount. The problem I have with that is that if at some point a net loss occured which wasn't accounted for, he may be replacing what he thinks it needs, but that may not be enough. He also mentioned some metal chips in the orifice tube, so he went ahead and replaced the orifice. I thought I read in my literature, there was a tech bulletin suggesting the installation of a screen at the compressor inlet to collect any shavings and prevent damage to the new compressor. The technician had never heard of such a thing or so he said, he may not have understood what I was asking.

If I run through all the hardware and I'm confident nothing is rubbing, loose, etc. and it still makes the noise, my plan is to seek out a professional A/C shop. I wish I could work on the A/C system myself, but its virtually impossible without proper evac / recharge equipment.

I may also throw a new water pump on, simply because I happen to have an extra one.

BTW as a last comment, I do understand that the compressor is a variable displacement compressor. I'm not a mechanic so I really have no idea how it works internally, I would love to get my hands on one to take apart for kicks. Unfortunately they always have to send the old part back so delco can sell it to someone else, lol.

BNaylor - let me respond to you're question also. I know the typical moaning sort of sound that varies with the weather conditions and loading, etc. If you can imagine revving up to redline and then hearing a few pulses like someone pressing the button on a coffee grinder, that's what I'm hearing, and its that loud too. Passengers in the car ask me if the engine is going to blow up. Unfortunately I have to say "we'll see", lol. Frankly if this weren't associated with the A/C on/off I would immediately suspect something in the exhaust system, like a heat shield or even a worn out cat, perhaps even idler pulley bearings. I've hit the catalytic converter with a rubber mallet to see if it's rattling and it seems nice and tight. Of course I would expect to hear that more at idle, but you never know.

Is there anything I should check on the accessory loop, some test I can do besides just feeling each of the pulleys? I'm not sure if there is something I should be checking on the harmonic balancer? I would say the pulley's feel smooth with the belt off, the water pump has a bit of play in it, but it doesn't feel drastic enough to cause what I'm hearing.

I don't know enough about that clutch mechanism to say whether it is loose or not for sure. When I tap on it with the engine off I don't detect any rattle. With the A/C off it certainly doesn't rattle, and at idle with the A/C on it doesn't seem to rattle much either. We're now on compressor #3 too if you count the original, so I would be surprised if all three just happened to be equally loose in the same way.

Perhaps the belt tensioner is somewhat dried out. Have someone rev the car hard while you watch it and see if it vibrates/shakes and also see if you can hear where the sound is coming from while you are near the engine. If it is as loud as you say it should be obvious as to the general area it is coming from.

Interesting, I have the same problem except it doesn't depend on the a/c being on or off, just does it randomly and always when starting off from a dead stop. The whole front end shakes and shudders for about 5 seconds, then returns to normal. It's worse if you accelerate hard, but it's always random, most of the time it runs perfectly. Also sometimes does it when doing a hard pass as well. Maybe a trans. issue? Fluid is perfect.

Interesting, I have the same problem except it doesn't depend on the a/c being on or off, just does it randomly and always when starting off from a dead stop. The whole front end shakes and shudders for about 5 seconds, then returns to normal. It's worse if you accelerate hard, but it's always random, most of the time it runs perfectly. Also sometimes does it when doing a hard pass as well. Maybe a trans. issue? Fluid is perfect.

It could be engine mounts or something else mechanical but it could be a tranny issue if you are getting it from a dead start. The front end will shake and bounce badly. It is called launch shudder which is normally an issue with transmission line pressure. Normally the pressure control solenoid - PCS not working properly.

What does it do in 1st gear (D1) in manual?

I am having a similar problem with my 2000 LeSabre. When I accelerate the engine sounds like a jet engine taking off and the noise will die down as I apply pressure to the brakes. It does not make any noise if I am at a complete stop. Just while in motion. Did you ever find out what the problem was? If so maybe that could be a good place for me to start looking.

I tried shifting into 1 when it happens, and it instantly goes back to normal when the lever gets to 1. Again, this launch shudder seems to be completely random, probably 95% of the time it is normal, but every once in a while it shudders when starting from a stop. Is this an easy fix, or does it involve taking the trans apart?