Grinding Noise From Under the Hood How to Check the AC Compressor

All right. Let's see if this thing starts. Oh, great.

Hey, friends, it's Len here from 1A Auto. So, we just went to start up our truck and what happened here as soon as the truck started was a loud grinding noise coming from underneath the hood. Obviously, that's something that I'm going to want to diagnose because I want to make sure I'm as safe as possible while I'm driving down the road. So, to get started, let's go ahead and pop the hood, take a look, and then we'll start it up and give it a listen.

So, now one of the first things I want to do under the hood without the engine running is just quickly inspect around all my pulleys and, of course, my belt routing system just to make sure that there isn't any debris or anything caught inside or around the pulley/belt. This looks great all the way around. I don't see any sticks or rocks or anything else that might've made their way up on there. So, now, let's continue.

Okay. So, now that we gave everything a quick visual inspection, we need to continue on by starting up the truck and then we're going to move along to listening to things. I'm going to do that with either a stethoscope that looks like this, but not everybody has one laying around their house. So I'll set it aside. Or you can use a long screwdriver or even a pry bar. Whatever you've got, just make sure it's long enough so you're free and clear from anything that might be moving such as your belt routing system in general.

So, now, let's start the vehicle and then we're going to try it with the AC on and with the AC off. Now, with the truck running, we want to go over there with the bar and we want to try to put the pry bar directly up against whichever unit is we're going to be testing, but far enough away from the pulley that it's not going to hit up against the pulley or the belt. Once it's up against there, go ahead and put your ear against the bar and just listen for any types of noise that sound irregular. So, now once you've listened to as many pulleys as you can safely, we're going to continue on by turning off the truck. Now, once the truck's turned off, we're going to come back underneath the hood and we want to pay quick attention to the belt routing. If you need to go ahead and draw a picture or take a quick note, whatever you need to do, but after that, we're going to remove that belt. Now, with the belt off of here, let's continue on by grabbing onto all of our pulleys, give them a nice wiggle up and down, left and right, and, of course, give them a spin. We want to listen for any type of noise that sound like they're irregular, such as the grinding noise that we heard with the truck running. Well, we definitely confirm that this is definitely an issue.

Okay. So, at this point, we've definitely confirmed that the AC compressor is the issue. There's going to be clutches that are supposed to be involved with this, and they typically go bad. That's what's generally going to cause this grinding noise, especially when the truck is running, obviously. Since we have the belt off there, we want to take a quick inspection of this as well because we checked all the pulleys, we wanted to make sure that none of those are bad. That's going to be very important because who wants to replace the AC compressor and not know that they have something else wrong with one of their other pulleys or even their belt? To inspect the belt, generally, you can look at the back of it. And if you see any discoloration or shininess, usually, it's a pretty bad sign. But generally, if you were to turn the belt around so you can see the ribbed area, usually you're either going to see some cracks inside there if the belt is bad or you might even see that these grooves right here are worn very deep. If they're worn deep, that's telling you that the belt is actually worn and it needs to be replaced. This one should be replaced.

Replacing the AC compressor, overall, isn't necessarily the hardest job, but there is a couple things that you need to think about along the way that's going to kind of make it one of those things that makes you maybe not want to do it in the driveway. Essentially, what the problem is is it comes down to your refrigerant that's going to be located inside of your AC compressor/inside the AC system. The refrigerant that's located inside the system is, of course, going to be under pressure. So, essentially, if you were to just go ahead and disconnect any of the lines from the AC system, you're going to have it under pressure and it's going to want to go someplace, potentially in your eyes, your mouth, or even in your lungs. Aside from that, not just on you, it's going to eventually make its way up and into the atmosphere, which, of course, could cause an issue with the ozone layer and, of course, contribute to global warming. And not to mention that it's actually illegal to evacuate your AC system into the atmosphere. Now, with that said, obviously, to be able to service your AC system, you're going to need to have some sort of machine that's gonna be able to evacuate the refrigerant that's inside the system and then, of course, replace it once the service is done. The machine is not necessarily going to be something that everybody just keeps in their shed or their garage just in case they ever need to do an AC service once in a while on their automobile.

So, now you need to think about, you're going to have to bring your automobile to a service station so you can get the service done. Now, essentially, if you were to ask around a couple different places, you're probably going to get a couple different quotes on that. And some are going to range from low to maybe even some high. Now, common reasons why you might find that you have a higher quote at some service stations as opposed to some others might generally come down to there's a lot of other things inside your AC system that maybe those stations want to replace and it's probably a good idea. Now, the reasons why you'd probably want to replace a couple other things and not just the AC compressor on this particular issue is because of that grinding noise. If, of course, there's grinding noises that are coming from the AC compressor, there could also be contaminants that are floating around inside the AC system. Now, as part of the AC system, there's going to be a couple different areas that act almost as though there are a filter of some sort. You're going to have an orifice tube on most systems. And that basically is like this little itty-bitty tube that has a whole bunch of little screens on it that's supposed to filter out any type of debris that might be inside the system. If, of course, there's too much debris because something happened inside of your compressor and it's causing this issue, if it floats around, makes its way to that orifice tube and clogs it up, you're going to be building up too much pressure inside of your system and, of course, you're going to overheat the system, and probably overheat your brand new AC compressor as well. And there's going to be some other parts of your AC system that are going to have small passages through them, such as your condenser or even your AC evaporator. If any of those passages get clogged up with debris, obviously, you're going to have another restriction and once again, an overheating condition for your air conditioning system. Something else we want to think about is your AC receiver dryer. This is typically something that you should generally replace every three to five years. It really depends on your automobile. Typically, what happens with this is, of course, if any contaminants get inside there or if the drying agent that's inside here isn't actually accumulate the condensation the way that it's supposed to, it's going to cause a major issue with your AC system. So, if you know that you're having an issue and you know that you have contaminants inside your AC system, it really makes sense to your AC receiver dryer as well. And, of course, you have a whole bunch of AC lines that are going to be running to and from other parts. So, of course, if anything like that has contaminants in it, that's going to be an issue as well. Typically, you can go ahead and try to flush out your AC lines if you have a special flushing system for that. But overall, if you have something that looks like this, it's more than likely just going to have to be replaced.

Okay. So, that's a short list of a lot of things that you're going to have to replace with your AC system, assuming that you have some kind of contaminant in there. Overall, if you have an older vehicle and you're not necessarily worried about having air conditioning, you can just go ahead and get rid of all this, put in a bypass pulley, and essentially, that's going to make it so now you don't have any air conditioning, but you also won't have any grind noise coming from your AC compressor. And if you're the type of person that really cares about your air conditioning, obviously, you're going to want to try to do this right. Just replacing the compressor without replacing anything else, it might work for a little while, and good for you if it does, but it might not last for very long. Once again, if those contaminants are floating around through the system and getting caught inside some of the filters or restricting flow in any way, you're going to overheat your system, you're not going to have very good air conditioning, and more than likely you're going to end up replacing everything again anyways.

Okay, friends, so we found where the noise was coming from on our particular vehicle. It came from the AC compressor. I also went over a couple other things that I would think about if I found that I had an issue with the AC compressor. Of course, you can go ahead and replace only the AC compressor, like I said, and nothing else and keep your fingers crossed. Or for me personally, I would look into a little bit further and, of course, make sure that there's no debris in the system. Well, if you like the video or you got something to say, make sure you leave it in the comments section below. Click on the like button if you like it and, of course, subscribe and ring the bell, that way there you can be kept up with all of our latest content. Thanks.