I have a couple questions about the ac compressor on my pathfinder. Current mileage is about 135,000.

Several weeks ago we started hearing a knocking noise from the engine compartment. It was mainly audible when coming to a stop, stopped in gear, or idling in park. It was random. First thought is that it was the engine knocking. I checked the oil and it looked fine...no particles or anything out of the norm.

Meanwhile, trying to find time to get it to the dealer so they can narrow down the culprit of the noise, another noise arose. It is almost like a grinding sound, like worn out break shoes rubbing on the rotor, but not a squeal. This sound is DEFINETLY coming from the ac compressor. While looking at it this past weekend, I noticed the grinding sound, and knocking sound coincide with each other. When the ac is turned on, the grinding sound and knocking sound both subside, to an extent. Both sounds are still present, just not as loud/bad.....turn the ac off and they pick back up, and it sounds awful.

I decided to crank the truck without the belt to make sure its not the engine. I took off the belt, and started the truck.....ZERO noises. I turn it off, put the belt back on and the noise is immediately present after I start it back up.

OK....I have several questions.

1) Is it possible that the noise is caused by the clutch/pulley bearing? Or is it the compressor itself making the noise? If so, can I replace the pulley/clutch and it fix the problem?

2) If you think that is needs a new compressor, should I go with new or a remanufactured unit? The reman unit I'm looking at has good reviews and is $100 cheaper than the new unit. If it was a $50 difference, I'd go new, but 100 bucks is a good bit of $$$.

a mechanics stethoscope can be very useful for tracking down noises

I know, but I am almost positive the noise is the ac compressor.

You can replace just the clutch, but for what it would cost to purchase a new clutch, you can go to Rockauto.com and, for a few dollars more, get a brand new compressor assembly w/ the clutch and not have to worry about removing and installing the clutch nor shimming the clutch to get the clutch air gap correct.

smj999smj wrote:You can replace just the clutch, but for what it would cost to purchase a new clutch, you can go to Rockauto.com and, for a few dollars more, get a brand new compressor assembly w/ the clutch and not have to worry about removing and installing the clutch nor shimming the clutch to get the clutch air gap correct.

What do you think about getting a remanufactured unit, instead of new? It will save me about 100 bucks, comparing apples to apples as far as the brand of the unit.

I am also curious to know if I should replace the expansion valve(s) in the process.

Also, how many expansion valves are there? 1 or 2?

If you have rear A/C, there are two expansion valves in the system; if you don't, there is only one. Personally, I wouldn't replace the expansion valve(s) unless pressure testing has confirmed it is not working or if there is metal debris in the system, in which case the system should be flushed. If it is just a noise issue, I would leave them be. I would, however, replace the receiver/drier as it is the filter of the system and may be needed for warranty compliance of the compressor. Some warranties may also require replacement of the expansion valve(s), receiver/drier and proof that the system was flushed, so read the fine print if warranty is something that is important to you.

As far as remanufactured compressors, it would all depend on who remanufactured it. If it was a reputable brand, like Denso or Four Seasons, I would consider it an option. The OE compressor is made by Valeo, which also happens to be the least expensive, new compressor at Rockauto.com @ $180. I know on Ebay you can get a reman unit for $107.99 from "The A/C Compressor World," but who are they? They do say they are remanufactured in the US, which is good, but I'm never heard of them until today. Even cheaper, you can go with a used unit, but we all know the risks involved with that. On the plus side, you can get an OE part and if it gets past the first 30 days, you'll probably be good.

Thanks for the input. I think I am going to pass on the expansion valves, but I will definitely be replacing the drier. After some searching, I found a new unit for $150 on ebay. It is made by Universal Air Conditioner. From the reviews I read, it seems like an ok manufacturer, although they are manufactured in China.

I would pay the extra $30 and get the Valeo. At least with that you'll get a part from the company that supplies the original part to Nissan. Plus, Rockauto is real easy to deal with when it comes to returning parts if there's a problem under warranty.

Well, the compressor clutch was on its last leg. I had a friend that is supposed to help with the ac work come over and do the evacuation. We were going to do everything this weekend, but the clutch was not having it. I had him evac the system, I disconnected the lines, and put the new compressor on, just to use as an idler pulley until we can wrap of the repair this weekend...He didn't have enough time to do everything else the other day. I left everything unhooked from the compressor (lines and connector for the clutch) and just taped up the ends of the line really good.

The noise is completely gone and it is a lot less embarrassing to drive now. The clutch on the old unit seams to have overheated and cause the plastic around the coil to melt, causing the wires to come somewhat unraveled. The bearing seems to be shot, which I suspect is the cause of the heat, which led to the melted plastic.

Now, to my question. How in the heck do I remove the drier? This will be done this weekend, when we begin to wrap up the repair. I found where it is, I just don't see an easy way to get it out....or the proper way to remove it. Its located behind the driver side headlight, basically.