ndamenti

Hello-

I have an 2008 Acura TL (standard model, not Type-S). Recently I noticed an intermittent loud buzzing noise coming from inside the engine compartment. Upon further investigation, I determined that the noise is directly related in some way to the engine cooling fans.

Here's what I've observed. With the engine running, I'd see the engine cooling fans not running. Then as soon as the engine cooling fans would turn on, a loud buzzing type noise would begin, originating somewhere near the passenger-side engine cooling fan (right side of car). This loud buzzing noise would persist for a couple of seconds, then the fans would stop. There would be several seconds of silence while the cooling fans are stopped, then the engine cooling fans would cycle back on again and the loud buzzing sound would again commence. Then the cooling fans and the buzzing would stop again in a couple of seconds.

With the engine off, I tried rotating each cooling fan and each seems to rotate just fine, without any resistance. Also, it didn't appear that the buzzing sound was coming directly from either of the cooling fan motors.

I'm guessing there's some sort of fan control component that's gone bad here, but I'm certainly no expert as to what it could be. Any ideas? Thanks for your help.

VisualEchos

iTrader: (1)

I have this exact issue now. Did you find a solution?

ndamenti

No, I haven't found a solution yet. Still looking. Thanks.

ZOMGVTEK

If the fan is making noise but not visibly hitting anything, it's probably the fan motor.

VisualEchos

iTrader: (1)

It's not the fan motors, or the fans at all. The next time this happens, turn the car off, then put it in the ACC position and you will see the fans come on, but no noise...

So, it's not the fans, it's just RELATED to the fans.

I'm still diagnosing, I'll get to the bottom of it soon, just been a bit busy.

ZOMGVTEK

It's not coming from the fan itself?

Can you get a video of this?

VisualEchos

iTrader: (1)

Yup, already have video, but it's on my phone. I'll see if I can upload it to my thread soon.

Don (Turbonut) has been helping me pinpoint the noise in PM. I'm also going to Honda on Saturday, so I'll ask their opinion too.

The 3 important bits are:

1. Related to the HVAC fan, but not the HVAC.
2. Related to the cooling fans, but not the fans.
3. Noise increases with vehicle speed.

The noise is directly related to whatever clutch attached to the motor kicks in to run the cooling fans.

ZOMGVTEK

Does it have anything to do with the A/C?

The fans are purely electric and mechanically isolated from the engine. They can still make noise that would vary with the engine speed thats not caused by the fan itself, but it would most likely be due to poor regulation on the electrical systems part most likely caused by a failure or very high electrical load. In cold weather this could be due to a battery fault, such as high internal resistance or even very low state of charge.

Did you only notice this in cold weather? Would you call it abnormally cold for your area and what you generally use your car in? Does it change tone with the HVAC fan speed? Does it change with the headlights on or off?

VisualEchos

iTrader: (1)

Not that I can tell.

My battery is less than 6 months old.

I actually noticed it back in the Summer. It presents in the cabin as a whine of sorts, that increases with vehicle speed. Almost like gear whine, but much more faint.

No, and the sound does not change with temperature. It has done this at 85°, and at 5°.

No, the HVAC is unrelated, other than when you turn the fan on it kicks the cooling fans on if they weren't already. Not sure why that is, but it does, even if it's straight heat.

No.

My gut feeling is that it's an idler/tensioner.

ZOMGVTEK

So, you're saying it has nothing to do with the cooling fan whatsoever, and is not coming from the cooling fan or HVAC fan?

If it's repeatable enough, the logical step would be to remove the drive belt and see if it goes away, put it back and it should come back. Then determine why. Or it could be the timing belt or auto tensioner under the covers.

wrecklezz

I had this problem and believe it or not it ended up being the serpentine belt tensioner. not the pulley but the arm itself.

VisualEchos

iTrader: (1)

Exactly.

This is exactly what Turbonut (Don) said. Good advice, thank you.


Thank you! This makes perfect sense! I'll ask Honda about it tomorrow.

VisualEchos

iTrader: (1)

Well, bad news on my end, hope it's not the same for the OP.

Honda says it's either the clutch and coil for the A/C compressor, or the compressor itself. Apparently, even if you're only using heat, the A/C compressor still cycles, and that's where the noise is coming from. Bummed.

Now I've gotta' see if this is a common problem, and how I might be able to save some coin on it.