Anyone taken their truck in for an underhood "whistle" noise from their AC?

Now that the temps in Phoenix are getting back to their usual Phoenix-y highs, I've been using my AC a lot more.

Does anyone else's AC occasionally make a short whistling noise? It's usually a shift or two after leaving a stoplight (not hard acceleration), or on the highway it will happen even if you are not accelerating, just maintaining speed. It's like a "whhhhoooooooooop!" that lasts about 2-3 seconds coming from under the hood, not in the cabin. If you were listening to music loud enough you wouldn't hear it. Definitely not a belt slipping.

My truck has made this noise from day 1. I haven't taken it in simply because there is absolutely no problem with the AC. It will freeze you out if you crank it. I've also had other vehicles make similar strange noises from the AC system and they've never failed on me either.

Again, no issues with temps, I'm just curious if anyone else has taken their Tacoma to a dealer over it, and what did they say?

My guess is that it is the AC lines vibrating, kinda like old water pipes groaning.

 

I have the same issue and also live in the Phoenix area. I only hear it at highway speeds sometimes if I have recirc off but I just figured it was a quirk of my truck.

 

Funny. My wife rode with me today and confirmed what I thought I was hearing - which is as you described.

Glad to know what it is. And it's not just Phoenix....

Could it be a 2.7 thing?

 

My guess it is from the inside, within the evaporator box inside the dash.

The expansion valve functioning in a normal way.

Your "whhhhoooooooooop!" that lasts about 2-3 seconds coming from under the hood, not in the cabin. If you were listening to music loud enough you wouldn't hear it" is what I base that on.

Classic for many vehicles that are blessed to be still using expansion valves instead of orifice tubes.

 

I have TRD off road, so I don't think it's specific to the SR/4cyl.

 

AFAIK the AC is the same in both vehicles. Waste a lot of money to have two different systems, and we all know Toyota isn't into that.

 

I was in Phoenix last week on business, heard it was going to be 108 today, (glad I missed that) . If your system is operating properly and you are happy with it. Dont mess with what isn't broke.

 

Yeah I checked out the parts catalog this morning and the compressor is the same, at the very least. Didn't bother to look much past that. If my guess about the lines making the noise is true, it could be a 2.7 specific quirk because I do believe some of the compressor lines run a different path to clear the V6 versus an I4.

Man, I could swear it was under the hood but I guess the noise insulation is better than I realized. Is it confirmed that Toyota trucks still use expansion valves and not orifice tubes?

This is starting to make a lot more sense now, though, because I have a different AC-correlated noise that almost sounds like extremely quiet valve tap you can sometimes barely, barely hear at idle (radio has to be OFF) that I thought was coming from under the hood, but if I roll down the windows to try to listen for it, nothing...

It's funny, the 2.7 is so boringly reliable you start hearing normal things (tap of that PWM vacuum valve, whoosh of the secondary air pump, AC noises) and start thinking "what is that?!?!"

I'm not taking it to the dealer. I was just having a bored Sunday morning and posted up to see if anyone else has it / has figured out what it is.

 

I've had several Japanese vehicles since the late 80s, have never seen an orifice tube.

Could be the units I had. Or not.

A stethoscope on the evap box worn by a passenger should confirm. Or take a drive with the glove box open and the cabin air filter removed. That should make it more noticable.

 

My V6 has made this noise from day 1 also. Definitely related to the ac, and its normally when the compressor kicks on while accelerating through a gear at mid range RPM.

 

Yes, took my 2018 Tacoma 4 cyl 2.7 in for whistling noise with only 350 miles on it. They couldn't duplicate the sound. Asked dealer to check trans fluid level, but after talking to the tech it was obvious he didn't check per Toyota specifications (warm up to required temp range, remove overflow valve, etc). Plugged holes in front lower control arms per TSB, didn't help.
Sound is intermittent, and stops when I turn off the AC. At 1,000 miles now, still having the problem, hoping it's not the transmission.
Going to another dealer to have the fluid check done right.

 

It's definitely not your transmission, so don't worry about the whistle being related to transmission. I have had my transmission fluid properly checked (factory fill was good, March 2016 production) and I still have the A/C whistle. I'm not surprised one bit you got the "cannot duplicate" line though, for such an intermittent sound.

Since we've confirmed that many trucks have this whistle and none have had any actual issues with AC failure so far I think we can safely chalk this one up to "strange but normal."

 

My AC does this also. Doesn't concern me. I don't use my AC much anyways.

 

I've noticed a very similar issue. Hear a whistling sound after accelerating from a stop light, I occasionally hear it while driving but now as loud. Just bought my first Tacoma 2018 SR. A little concerned about the noise.

 

Today was 95 degrees and it definitely did it more pronounced. Its always while the rpms are up or rising.

A/C cools good though.

 

It is the A/C compressor resonating at a certain rpm under certain conditions. It happens for a few seconds because the compressor cycles on for only a few seconds at above idle rpm. There is nothing wrong with the system whatsoever. It is not unique to the 2.7 but also happens on all models of the tacoma 3rd gen.

 

Is this the whooping noise you are talking about? The is the first thread I've found that appears to describe the sounds I'm hearing. I put up a video with 3 recordings of the sound here:

https://www.reddit.com/r/ToyotaTacoma/comments/95s8cy/help_identify_strange_noise_from_2002_tacoma/

It only happens once when the AC kicks in, particularly when idling at a stoplight. The high-pitched noise has gotten quite loud on my 2002 Tacoma. Is there any fix for this? FYI I had the blower motor replaced, so it's definitely not that. It blows cold air.

So it's not the AC compressor clutch? If this is the "expansion valve"/"in the evaporator box", is there something to be done there?

I'm trying figure out what parts would be related to only when the AC kicks in. Speculating here; the sound does seem consistent with one that would be made by compressed air. There's no grating sound and I haven't found any belt-related or clutch replacement videos that have a similar one-off sound. Perhaps it's a seal somewhere connected to the system? Where the gas exits the compressor? It seems to really be prominent in very hot weather, and outside temps do have a "massive" effect on the pressures according to this video about how ACs work .

 

That's not the sound I experience. Does not happen at idle and is not that short. Think along the lines of 2 full seconds of noise or so.

Sadly I can't offer you much advice on your noise. All I know is noises as described by me (in the OP) appear to be just odd quirks of an otherwise fully functional AC cycling on and off.

 

https://www.tacomaworld.com/threads/2018-tacoma-off-road-a-c-noise.550627/

 

Similar noise on my 2019 SR5 with 3.5l engine. Usually at highway speeds. Toyota did a lousy job when tuning this model for noise abatement.