Hello, I have a 2015 Honda Civic EX (automatic CVT) with 137,000kms. An issue started a month ago with a metallic rattle and I'm stumped. It seems very loud when driving by buildings with the passenger window open
The Noise Only Occurs:
- While cold/warming up, until it reaches operating temperature. The car sounds fine once fully hot. Also seems to be less severe if the outdoor air is warmer.
- In drive only, though if I spike the RPMs moderately in park/neutral I can catch it for a split second. Otherwise no rattle when revving in park/neutral.
- Only in the rpm range between 1200-1700rpm, under acceleration in drive and when crossing back down through the range.
- Taking the belt off and running it on a hoist under the conditions above (left overnight, in drive, accelerating to 1500rpms). The noise went away when the belt was removed, came back with the belt on.
- They replaced the serpentine belt tensioner twice (first with a Dayco then switching to OEM), replaced the belt, and idler pulley. The noise didn't change.
- Apparently ruled out AC Compressor and Alternator, though I'm still suspicious about that. They think it is the water pump but they aren't sure.
Accompanying the noise is a high pitch whine sound coming from the front of the engine, please see this persons reddit post below for a perfect example. This noise, unlike the rattle, occurs in idle, can often be "aggravated" but revving into the 1-2k rpm range, appears quite quickly after starting, and goes away entirely when warm. Possibly related??
https://www.reddit.com/r/MechanicAdvice/comments/1f6kmet/high_pitch_whine/
Thanks so much, I truly appreciate your help and expertise
I can go back to the shop and ask why exactly they didn't use a more advanced tool.
Some mechanics are just better than others, but they won't tell you that.
They think it is the water pump but they aren't sure.
A good mechanic would make sure, because there are ways to check. Sounds like they just slapped a new part on, took your money, and sent you on your way.
@imperator It really does feel like that. Though, they did spend several extra hours of shop time trying to further trace the noise (at no cost to myself), agreed to refund the labour for the correct part, and threw in a free pulley for the trouble. I do agree I likely need to seek out another opinion from a professional who deals exclusively with Japanese vehicles, but at least they aren't taking me to the cleaners intentionally. From the small bit of information I can find on this particular issue, it seems others affected are also having similar diagnosis issues after multiple opinions, but you're right, I can't imagine it's that tricky.
Thank you for responding, any and all feedback means a lot to me. I'll likely seek out a second (third?) opinion as both the dealer and this independent can't seem to pinpoint it, and then use the labour credit towards the correct repair.
so there's no noise when you rev it in park?
@imperator Strangely enough the loud metallic rattle demonstrated in the YouTube clips doesn't occur while revving in park. Though I was able to spike the rpm moderately to catch it for a split second in park/neutral a few times. There is a secondary noise, high pitch "wine" sound in idle. (see this clip: https://www.reddit.com/r/MechanicAdvice/comments/1f6kmet/high_pitch_whine/). Once the car has been driving for a good 30 minutes to an hour it stops making any noise, besides a "winding down" high pitch sound when coming to a stop and decelerating at slow speeds.
I imagine all these sounds are related to each other as they all began at the same time, though this car is new to me only bought a few months back. The metallic rattle, while only really occurring steadily in drive, does go away upon removal of the belt. The shop I went to said the AC compressor and Alternator are not the cause, though I do get slight dimming in the lights as the AC compressor cycles on/off while in idle/park, as well as when the RPM's settle after revving in idle/park. The tensioner, belt, and idler pulley are brand new, leaving the water pump and harmonic balancer as the only possibilities left.
@imperator I'll also add that for the people who recorded those YouTube clips I shared of the rattle, the solution was a new serpentine belt tensioner. They also had the exact same symptoms. Oddly enough, I have the exact same noise but a new tensioner didn't fix it? The nearest part is the water pump, as the shop used a stethoscope to pinpoint it to that area. Unless it's a motor mount or maybe even a worn thread in the timing cover itself, I really don't know. I had the tensioner bolts changed as well so that eliminates a mounting bolt issue.
Sorry for so much extensive detail, it's been quite the journey solving this so far.
Here's the thing noises can be pinpointed. See my video finding the source of car noises. Then either buy one of those machines or find a mechanic who is a real mechanic and has such a machine. That will definitely pinpoint the noise and since it goes away when you take the belt off it has to be something. The belt thrives. And it would certainly be bizarre if it was the tensioner cuz if they use say a cheap aftermarket tensioner they often make noise but you really have to pinpoint it
@scottykilmer Hey Scotty, thank you for the reply! I took a look at the video you suggested, so hopefully I can go back to the shop and ask why exactly they didn't use a more advanced tool. The tensioner they installed is OEM Honda, the belt is Dayco, though there was zero change from the original OEM parts. Would you have a gut feeling as to which component may be causing this noise?
The shop did use a traditional mechanics stethoscope and pinpointed the area of concern to be around the tensioner, though they claim it's difficult to confirm that the water pump is the culprit (given close proximity perhaps?), and wish to wait for more symptoms. After wrongfully assuming it's the tensioner, I don't think they want to chase it with parts. Thankfully, they credited all the labour towards the correct part once more signs appear. Regardless, I'll be sure to update this form when I finally have an answer.
All the best to you Scotty, thank you for your advice and for all the helpful content you posted through the years!
I imagine all these sounds are related to each other as they all began at the same time.
This is really confusing me. I though you just finished saying that the rattle starts when you put it in drive, and the whine starts at idle (presumably from when you first start it up). To me that sounds to me like you have two different unrelated sounds.
I do get slight dimming in the lights as the AC compressor cycles on/off while in idle/park
Well that's very telling. You should have mentioned that first.
I would have the electrical system (battery + alternator) tested.
Also: disconnect the AC clutch, and try rotating both AC compressor and alternator pulleys by hand.
The nearest part is the water pump, as the shop used a stethoscope to pinpoint it to that area.
those certainly can rattle. Is there any play in the shaft?
@imperator I apologize for that. Basically, say it's a cooler day. I'll start the car and it sounds fine. Then usually I'll put it in drive and head off. While the rpm's cross in and out of the 1500rpm range the metallic rattle will begin. As the car heats up, a high pitch buzzing begins (noticable in idle/when stopped) as the metallic rattle slowly starts to quiet down. Eventually, as the car heats up all the way the only sound left is a high pitch winding down noise as I decelerate towards stops, and that's the only symptom left at operating temperature. It's progressive as the noise changes likely under thermal expansion. The only reason I didn't lead with the alternator/charging system is the shop tested it and it was fine. I'll try to look into it further, but thank you again for your time and expertise.
I see. Noises that only occur while driving are difficult to diagnose. At least you know it's one of the belt driven accessories, so it shouldn't take long to narrow down.
The load on the water pump increases as the thermostat opens. You could try removing the tstat as a temporary diagnostic measure.
The dimming is a big clue. I would pursue that as well.