There is a large empty plastic reservoir directly below the front passenger-side headlight. What is it called and what purpose does it serve? I noticed that it looks like it was not properly attached while the car was repaired from a front passenger side corner bump a few months ago, and was wondering if I should take it to another mechanic to have it checked out (there is a strange hissing-like sound coming from that general area now after the engine is switched off for a few minutes especially in hot weather).
The large white plastic container is a resonator. The engine air intake passes through that container. It seems to be missing a hose that runs to the fender as an air intake. I would not leave that open fitting without the mating hose indefinitely as water might enter. The hissing sound is probably caused by the engine radiator cap venting a bit of pressure that built up after running the car in hot weather. I would characterize that as normal; however you should check the coolant level in the radiator as well as the overflow container when the engine is cold. Make sure the radiator is full and the overflow reservoir level is at the full mark.
—- Thank you! How can you tell that it is missing a hose? I do not see any opening on the container (at least from that viewpoint). Thank you for the tip on the hissing sound too. I think the coolant level in the radiator may be too low (there were probably air bubbles left after the mechanic changed my water pump) since I also hear some splashing when accelerating.
—— To answer my own question, I think you are talking about the large open fitting above the container. I am not sure if I can check whether the mechanics put the mating hose back on without removing the headlight. Is it possible to see it from above or below the car without removing the light?
Just above the white reservoir, there is a black hose that comes down through a flexible joint, then curves around towards the back? of the car, and then points upwards with nothing attached.
It appears to be missing the item with callout 17752, part number 17752-21050. As you can see, it gives the air intake a kind of protected, rear-facing inlet. Without it, you've got an inlet facing straight up, where it could slurp in rainwater, etc. You can also see that the air path doesn't go through the Helmholtz resonator, it goes over and past the resonator, the same way you'd blow on a bottle to play it.
Patrick, thank you again for the helpful response. On your second comment, I checked, and indeed the radiator was not completely full and the overflow container was empty. So I filled up the radiator and put coolant in the overflow container, then run the engine a couple of minutes to make sure the level doesn’t fall again. That fixed the splashing noise issue I have been having since a mechanic changed my water pump two weeks ago. However, I did not open the air bleed valve while topping up the coolant. Does it mean there could still be air in the system (though I hear no strange noises while driving any more)? Also the noise after stopping the car is now quieter, but still unusual I think. Can you tell what is it caused by and whether it is normal? https://share.icloud.com/photos/0_SUnDxOLaPTWkan5GU44VCcQ#Chevy_Chase,_MD
There may still be air in the system. Check both the radiator and the overflow reservoir in the morning when the engine is cold. Fill as needed. Repeat this check each morning until you find the coolant level no longer drops. That sound is not easy to hear on your video. Maybe it is due to air in the system, see if the noise persists after the coolant level stabilizes at the full level.
Thank you - the coolant level has stabilized now but I still have weird noises - I posted a separate threat for those, and I tried to make better videos. https://photos.app.goo.gl/a3hoSprrRUzXMwjZA
My 2010 has been making the same noises as yours in the 2nd video. Only audible when outside of the vehicle. Anyone have any clue as to what that noise is? It's a recent development for me.
OK, you have two different noises. The noise inside the passenger cabin is likely due to a stuck servo motor in the HVAC system, causing the clicking noise. If the stuck motor doesn't clear and you want to do something about it, that involves disassembling most of the dashboard to get to the stuck motor to replace it. Hence a costly job. If the air conditioning is working adequately, I would suggest you live with it. The noise in the engine compartment, like a teakettle whistling, is just the engine coolant system venting a little through the radiator cap. I would call that normal and the noise does not need attention.
Thank you. The AC works fine for now. Wouldn’t it get worse over time if I do not fix it or there is a chance it stays stable? What usually causes it to get stuck? When I brought the car for a check after the water pump change (when I heard the liquid splashing noise), the mechanic thought it might be a partially clogged AC drain and said he will clean it. As I established later with your help, it was actually inadequate coolant. I wonder if his cleaning of the drain could have caused the new clicking noise (which did appear since then). Thanks for responsive to my other threat too - I posted it separately for the benefit of others who may have similar noises.
There are three servo motors because there are three places where the air flow can be switched around: 1. Fresh vs. recirculated air (air inlet) 2. Dashboard vents vs. floor vents (air outlet) 3. Heated vs cooled air (air mix) The first question is which motor is sticking. If you play around with the various HVAC controls you might be able to figure that out. Then see if the sticking motor will free up if you cycle the operation back and forth. I had noticed this problem with my 2004 several years ago; then the problem went away. So it could get worse, better, or stay the same. Who knows. Its not obvious to me how the cleaning process would damage a motor, unless the cleaning fluid was introduced past a vent door and the fluid made its way to the motor shaft and caused friction or binding to occur.
Gen 2, like Gen 1, has three A/C servos, and two of them are on the easy-to-reach side of the heater. Only the one for fresh/recirculated air is on the hard-to-reach side, with tedious dash excavation in the way. In my experience, like so many things in Gen 1 and Gen 2, the A/C servos don't get noisy because of the motor "sticking". They make (sonic) "noise" because of (electrical) "noise" in their position feedback sensors. They are just potentiometers, and they need some attention with electrical contact cleaner after a while. They are sending back a jittery electrical signal to the HVAC controller, supposedly reporting the "position" of the air flap. The controller, of course, is trying to keep the air flap in a specific place, so as it sees the "position" seeming to jump around, it sends signals back to the motor trying to keep it in one place. Of course that just makes the motor skitter back and forth, making the noise you end up hearing. Assuming the servo that is jittery is not the hard-to-reach fresh/recirculate one, taking it apart and cleaning up the electrical contact paths makes for about a twenty-minute job. In Gen 2 it is a little harder than in Gen 1, just because there's an inconveniently-located ECU down there in Gen 2, in the way of one of the mounting screws. yitznewton found the solution for that.
