I recently noticed a high pitched humming noise when I put my car in reverse after it has sat stationary for a long time (like in the mornings, or after a work day). The noise fluctuates in frequency, and isn't really a whine, but more like a humming noise and it lasts for about 10-15 seconds. It isn't dependent on if the car is moving or not. If the car is in reverse and isn't moving, the noise occurs. Not sure if it's a electrical humming noise or not, but it's not my rear view mirrors.

Not sure if it's due to the 3x3 transmission flush I had a few weeks back. I didn't have the noise until I got the 3x3 transmission flush, although the noise did not occur right away after I got the flush (if I remember correctly).

But other than that, it runs great...

 

Hopefully, it is the brake pad wear indicators. Mine did this only in reverse and was a high pitch squeal. Brake pads needed to be replaced.

 

I check all my pads, and they still have about at least 5mm in them, so they are still very good. I thought about the brakes too, but I just find it odd how the sound will occur if they car wasn't moving. I think I'll let go of the brakes fully to see if it'll occur tomorrow to fully eliminate the brakes from the list.

 

It is because the RL is 4X4 not 3X3!

 

So if you start it and it idles for a minute or so, it doesn't make a noise? Then putting it in reverse it make the noise?

It sounds to me like something charging up, per se, like a power steering pump.

 

Something like that. As long as I keep it in park and just idle there, there's no noise. But once I put it in reverse, the noise starts. I just find it odd because I never had it happen until a couple weeks ago. I'm gonna see if I can tell where it's coming from today.

 

hahaha please tell me you are not serious?!

 

It could be simply a bearing that wasn't being lubricated before finally getting some lubrication after the 3x3 process. Did you use Honda Z-1 or ATF-1 or what fluid?

FYI 3x3 means you drain and refill the trans 3 times since the transmission will only spit out 3 of the 7 quarts it holds at a time.

 

I used the new fluid that came out in 2011. It's ATF DW-1. It's kind of odd that I noticed it's easier to hear with the door closed as opposed to it opened. I haven't had a chance to try and hear where it's coming from today, I'll try tomorrow.

 

are you moving in reverse or just stopped

 

I was hoping this was a bad AWD joke.

 

eh sorry - add some smiles man

 

FYI - I am not often serious.

 

Just stopped, I heard it in park once too, although very faint. I don't know, it's weird because the noise stopped like for 2 days, of course it's when I wanted to see if I can isolate where the noise is coming from. But it came back this morning.

 

I think the noise is coming from the fuel tank unit which includes the fuel pump, fuel pressure regulator, fuel gauge sending unit, fuel filter, and transfer fuel pump. Because I can only hear it when the door is closed, and I feel like it coming from the rear left of the car, which is where the fuel tank unit is located. And I also notice that it also occurs when I'm stepping on the gas for the first time in the mornings after I backed out of the garage.

 

If you shift quickly from park to drive, does the noise still occur? I don't think this diagnosis ^ is plausible if it doesn't. Back into your garage and see if it does it in drive.

 

Hm, that's a good question! Did not think of that, I shall try that tomorrow and see.

 

So I gave it a shot and put the car in drive right when I started it, and yup, it makes the same noise. Hrm....

 

I just noticed the same problem with my 2006 TSX this morning. Was there ever any conclusion to this?

 

Fuel pump system.

Mine does it, sometimes louder than others, but I usually only notice it when in the garage.

I was able to demo it for my Tech at last oil change. He confirmed the sound was the fuel system delivery being regulated for ULEV 2. The fuel pressure / delivery is being balanced with ignition sothe least emmisions are being generated....mostly an issue at start up.

He actually demo'd the same sound on another RL, MDX and and TL.

 

Do you and your tech go out for steak and beer or something?

I need a tech like that.

 

they are huggers... of what I have no idea.

 

I have only one Tech that services my RL. I schedule my appointments around his work schedule. He treats me (and my RL) very well. Nothing is too small for his attention. He has told me he appreciate the knowledge I have of the car and not the typical customer that walks in suspicious about everything and wigs out when there is a repair needed. I am fortunate to have a great Service Adviser, Tech and Dealership. I know that was a jackpot in terms of the auto industry.

That said, it was only after he demon stated to me his level of detail and spoke to me in depth at a routine service call, including taking me back into the garage to show me what he was doing on my RL....it was then I treated to burgers and beer. Periodically I show up at the dealership with 5-6 pizzas and one for my Tech goes straight back to him in the garage. On mornings of my appointments I bring donuts for the service center staff. I once gave him a gift card to a nice restaurant when he stayed late to finish work on my RL (I was leaving for Antarctica the next day and had no way to get the car home as I was gone for weeks). He told me the dinner treat help calm his irritated wife!

It has paid dividends. I trust the info he tells me and sometimes he advises to buy a part on my own and he will install at significant savings . Such is the situation with the HID bulbs I just bought that he will install for me Saturday. Considering what Acura would have charged me for the bulbs alone, a steak dinner and beer is covered, many times over. A level head, patience and kindness can go a very long way.

 

So, did you figure out the issue?