Intermittent noise in 2003 Honda Civic that no mechanic can diagnose

Hi all, I am new here and have a question. About 3 weeks ago, I purchased a 2003 Honda Civic EX Coupe, automatic transmission with 131,000 on it. I took it to my mechanic before purchasing it and he said it looked good. The test drive didn’t reveal any problems. A few days into owning it, however, I noticed this screeching noise but it didn’t happen all the time. When it happened, I was always taking off from an intersection or pulling out of a parking lot - never when I was just driving down the road or on startup. The mechanic couldn’t get the noise to happen but inspected the belts and said they looked new and were tight enough. This continued happening intermittently and sometimes I would even notice a slight hesitation in the car on takeoff. I went back to my regular mechanic with no success and also took it to another mechanic who tightened up the power steering belt a bit - still does it. None of the mechanics hear the noise when they drive it because it is so intermittent. I will add that the noise only happens with the AC on - a further inspection revealed the pulleys to be ok. What in the world is this noise and is it something that could leave me stranded? Everything I read about screeching is belt and pulley related but that doesn’t seem to be my problem.

Try changing the belt. You can’t always tell if a belt is good by looking at it.

Which belt? There is more than one on the car. I am no mechanic so I don’t know the first thing about changing a belt and would certainly need to know which one to tell someone else to change.

The belt that drives the air condtioning compressor.

Ok thanks - I’ll see if they will be willing to change that one.

Good idea to change the AC belt, inexpensive & worth a try. There’s other things that can cause this type of under-hood noise too, like faulty idler pulleys, or faulty bearings in the belt driven accessories, like the alternator, water pump, power steering pump, etc. My first guess would be the power steering pump, as when you are pulling away from an intersection you are more likely to be turning at slow speed, which puts a load on the power steering pump. Next would be the water pump, as increasing the rpm increases the load on the water pump. There isn’t any load increase on the alternator or AC I can think of when pulling away from an intersection, but the rpms increase in both accessories, so it could be one of those too. If you can get it to happen when the car is idling in the driveway, a mechanic can use a device to isolate where the noise is coming from. If replacing the belt(s) doesn’t help, you may have to wait until it becomes worse. There’s a slight chance of a problem in the timing belt. Might be worth it to have that inspected too, esp if you don’t know when it was last replaced. Best to monitor the coolant temp and coolant level in the meantime.

Thanks George. I may start with seeing if they can replace the belt and go from there. I think the mechanics in my area (Western North Carolina) are generally honest and don’t want to charge people unnecessarily. They have checked the pulleys and bearings but it’s always possible they overlooked something. Power steering pump is a thought - I also own a 2000 Honda CR-V that had the power steering pump go bad a few years ago and the noise was different in it, but maybe every vehicle is different. As for the timing belt, I asked the individual I bought the car from and they said they had changed it around 110,000 miles - maybe should have asked for a receipt. Coolant levels and temp seem fine, at least for now.