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08 Highlander AWD (Serious Wind Noise When Rear Window Down)

audifansaudifans Posts: 8
edited April 2014 in Toyota
I just bought a used 08 Highlander AWD (Prior Rental) Its run great and very quiet on the road. Its handle a lot like a Audi Quattro, much better than just two 2 wheel drive , in my humble opinion. I own the car for just couple days. To my surprise when I lowered the rear window, at above 40 mph, the wind noise was so loud, I thought a Helicopter is hovering behind the car. Took its to a local dealer for a test drive and mechanic told me everything (drivetrain) is quiet inside the cabin when the rear windows are up. My wife sit in the 3rd seat and she sad its sound quiet too. Please give feedback thanks


  • steverstever Posts: 52,462
    It's a pretty common problem and there's not much you can do other than playing with the windows. For example:

    tidester, "Volvo XC90 SUV" #930, 3 Jan 2003 9:19 pm
  • grahampetersgrahampeters AustraliaPosts: 1,786

    If you put the front windows down as well, its not a problem. Only drama is when you leave front windows up and drop rear ones. Buffets your ears badly. Solution is not to do so


  • kenlwkenlw Posts: 190
    this has been the case in every car I've owned. Lowering the rear windows without opeining one of the forward windows creates a huge "buffetting" caused by uneven air pressure inside.

    it's very normal on any vehicle.
  • typesixtypesix Posts: 321
    Same problem in previous Highlander body style(1st generation).
  • phrosutphrosut Posts: 122
    I believe it was wwest that made a post a few years ago that if you remove the rubber membrane that forms an air check-valve in the cabin exhaust vent, the problem goes away. That vent is behind the grille in the far rear side panel.

    I haven't tried it so can't verify that it resolves the problem. I just don't open the rear windows by themselves while driving. You can get the same noise from the sunroof under similar conditions (can't remember exactly because I never use the sunroof).

  • wwestwwest Posts: 10,706
    Removing the reverse airflow check valve only partially alleviates this problem. What really works is being able to open the rear quarter panel window/vent like most minivans have the ability to do.

    Personally I bought two outlet airflow vents from one of the larger Toyota SUVs and installed those as high up as I could in my rear quarter panels. Not only does that prevent the ear busting helicopter sound when our dog wants "his" window open but also helps to reduce instances of sudden unexpected windshield fogging due to inability for build up of cabin humidity.

    Slightly lower FE due to lost A/C efficiency due to improved cabin flow-through capability. But I make up for that by having the A/C compressor totally and COMPLETELY disabled when there is no need for actual cooling, mostly the winter months.
  • kenlwkenlw Posts: 190
    "But I make up for that by having the A/C compressor totally and COMPLETELY disabled when there is no need for actual cooling, mostly the winter months."

    this may be ok in some places but can be very dangerous in areas with any humidity. the compressor runs when you have the defroster selected to clear up the front windshield. In fact I used it tonight (Houston) and it was in the upper 60s at the time. Heavy "fog" condenses/collects on the interior windshield, by running the defroster with hte compressor dehumidfies the air and clears the windshield. You can adjust the temperature so that the air is warm, but running the compressor makes the air dry, which is what makes it clear the windshield.
  • wwestwwest Posts: 10,706
    There is no place in the WORLD where COLD air is ever consistently HUMID air, in point of fact that is a pretty RARE circumstance. On the other hand passenger cabin atmosphere's that have been "artificially" and unusually humidified are quite commonplace, have BECOME more commonplace.

    Use of the A/C only for dehumidification when the OAT is below your comfort level is FRAUGHT with HAZARD...!!

    When you shut down the car for the evening the moisture, thin layer of moisture, remaining on the evaporator vanes, typically 10,000 square inches thereof (3-4 times enough to coat your windshield over to the point of no forward vision), from that day's operation will begin to evaporate. So within an hour or so the atmosphere in plenum area of the system will become SUPER-SATURATED with moisture, some of that, of course, escaping into the passenger cabin.

    So, now, the next cool/cold morning about 5 miles down the road the engine coolant will reach 130F, the system fan/blower will be enabled, and suddenly you will have a passenger cabin SUPER-SATURATED with moisture, and with any luck you will remain with enough forward vision while you wrestle with the problem. Otherwise you may, will probably, have to pull over to teh side of the road while you "wrestle" with teh problem of how to most quickly defog your interior windshield surface.

    Go to and read up on their EED, Electronic Evaporator Dryer, not just another way to prevent the formation of mold and mildew odor via the breeding of microbes within that dark, dank, and HUMID A/C plenum area.

    In the meantime you can avoid those instances of sudden early morning windshield fogging by lowering the windows slightly each and EVERY evening, provided you park under shelter. In the alternative you could discontinue the use of the A/C for other than actual cooling need.

    And what do you suppose happens if you drive from an area of normal humidity and reasonable warmth, non-freezing OAT, into an area of freezing temperatures and normal LOW humidity and the A/C compressor gets disabled "on the fly".

    I'm not against the use of the A/C as an aid in defogging, removing the condensation for a fogged over windshield. In the past the method used primarily involved the application of HEATED airflow and the A/C was considered an auxiliary function/aid.

    The thing, the major thing, that has changed is the size, density and complexity, of the A/C evaporator. Have a look at a typical passenger vehicle A/C evaporator of the early eighties and then one of today. One of the aspects that the industry has had to tackle to reach the FE goals was to improve A/C efficiency. More efficient A/C mean more complex heat exchangers/evaporators, and a time when available space behind the dash was shrinking dramatically (passenger side airbags, GPS/Nav screens, HID control/leveling ECUs, POWERFUL hifi radios/speakers, etc.) That also led, along with reducing NVH, well sealed and insulated passenger cabins, insulated and well sealed against air OUTFLOW (don't let that already "conditioned" atmosphere out of the cabin. Even the exhauster ports have been minimized in size to this end.

    Now you may begin to have a clue why the newer systems will not allow you to leave the system in recirculate mode in the summer if the A/C is not in use. And now more recently in relatively warm climates, 45-60F, wherein it is well known that the A/C may not be functional, certainly will not be FULLY functional, declining in dehumidification efficiency as outside temperatures drop.

    In any OAT, down to freezing, teh A/C may be efficient "enough", but you and I have no "sense" of when or where that might be the case, and so far the engineers have not found a cost effective method for accomplishing that task.

    So now you may find that even though the A/C appears to remain functional, keeps running all the way down to 35F, the system will not remain in recirculate mode for more than a few minutes if the OAT is below 50F. So it might be best to assume responsibility for your own life, and those of your loved ones/passengers, and DO NOT USE the A/C for any purpose other then the need to cool the cabin.
  • wlbrown9wlbrown9 Posts: 867
    How about RELATIVE humidity...completely different.

    Why do the mfgs program vehicles to have the A/C automatically come on when I hit defrost? To help defog the windows perhaps?

    Even with relatively cool air during those rainy days here in Memphis, hitting the A/C button will defog the interior windows within a minute or two. Then if I turn it off, they fog back up...this happens even after say 30 minutes of driving and the engine is warmed up and any residual moisture distributed.

    My older vehicle allow the recirculate to remain on even after power two newer ones require that you reset the recirculate after ever start if you want to use that.
  • kenlwkenlw Posts: 190
    suffice it to say you do not evidently know anything about air conditioning systems. I designed and built them for several years. Dehumidification is THE SINGLE MOST important feature of AC. Temperature control is only secondary.
  • wwestwwest Posts: 10,706
    Sorry, I was thinking Rh and should have said so.

    In yesteryear the use of the A/C as an aid to defogging, ONLY as an AID, automatically coming on in defrost/defog/demist mode was a quite reasonable action.

    Not today, no more.

    Think about what might happen, often does happen, once you leave defrost/defog/demist mode...

    The interior windshield surface fogs over again, even quicker this time.

    When you switch off defrost/defog/demist the moisture just previously condensed on the evaporator vanes will soon begin to evaporate into the incoming airstream, DRY incoming airstream in COLD climates. Therefore the incoming airstream will more quickly "absorb", SUCK UP", the evaporator condensate.

    The proper way, the only reliable method, for defogging the interior surface of the windshield is to HEAT the airflow flowing toward the interior windshield surface. That accomplishes multiple positive aspects things, heating the airflow will LOWER its RH, and then transferring some of that heat to the interior windshield surface will result in quicker evaporation of teh condensate and also help to prevent windshield fogging/misting.

    My new 1992 LS400 was so bad, horrible, really, at sudden instances of windshield fogging that I was forced to park it for two winters in a row until I could figure out the problem and thereby arrive at a fix.

    In the end I realized that I had to disconnect the A/C compressor clutch during the time period wherein I did not need cooling. I also built in a circuit and switch to cause the climate control system to "think" the cabin had suddenly gotten VERY cold. If the windshield started to fog over I would first activate the new switch and then activate the defrost/defog/demist mode. The system would then automatically go into MAX heat and max blower speed.

    With my '01 F/AWD RX300 came two new C-BEST features/options. I had the dealer set these options so I could disable the A/C indefinitely by simply switching it off once, the second option involved unlinking the A/C from automatic operation in defrost/defog/demist mode.

    With the RX's controls a quick clockwise twist of the temperature setpoint knob gets the system to max heat (by default, max blower) in preparation for subsequent, immediate, activation of the defrost/defog/demist mode.

    On the '92 LS400 I added two 12 volt fans, one in each rear quarter panel, that automatically come on in defrost/defog/demist mode, and with rear window defrost activation, to help remove the rise in cabin humidity that results from teh aforementioned actions.

    A bit of overkill, that, all one really need do is train yourself to ALWAYS slightly lower a rear window temporarily when using either function, front or rear "defrost".
  • wwestwwest Posts: 10,706
    ".. Dehumidification is THE SINGLE MOST important feature of AC.."

    That statement leaves me so FLABBERGASTED that I don't know what to say in response,.. almost.

    Let's totally disregard what I might wish say in response since that would surely get deleted.


    I am given to understand that we humans are most comfortable at an Rh of ~40% provided the surrounding air temperature and radiant "inputs" are also within our human comfort zone.

    I think you might agree therefore that dehumidification of a building's airflow might be at times, a highly undesirable "feature" of A/C operation. And what happens in say, Az when the Rh is sometimes, or maybe even predominantly, <10%

    Enough said...I will render no further response to kenlw.
  • kenlwkenlw Posts: 190
    that's good because my sides hurt from laughing at your illogic.
  • mdhuttonmdhutton Posts: 195
    Believe what you want to belive, wwest. Let me know how that ice scraper works on the inside of your windows sometime.
  • Regarding these outlet airflow vents, can you describe in detail (or provide a picture) of how/where you mounted them and the part number? Reason I ask is that I am also trying to alleviate that noise in our Highlander.

  • wwestwwest Posts: 10,706
    In my travels worldwide, including especially Fairbanks, Anchorage, Point Barrow, and Goose Bay, I have NEVER encountered ice on the inside of my car windows.
  • wwestwwest Posts: 10,706
    Toyota P/N is 62905-60050, louver, sub-assy. Mounted just below and at the rear of the rear quarter panel window that unlike most minivans will not open to alleviate this COMMON problem.
  • steverstever Posts: 52,462
    Happened all the time on my late 60's Super Beetle in Anchorage. My girlfriend (now wife) made me trade it in fact - she got tired of scraping the inside of the window. Pitiful heater. Maybe there was moisture in there somewhere, but it sure iced up.

    I've been to all those spots too. Was that you who cut me off in Happy Valley (or was it by the ACC store?). :shades:
  • wwestwwest Posts: 10,706
    Oh...... I see...

    That's the reason my '78 Porsche Targa doesn't get to go out much to "play" in the winter snows. Saying it has a cabin heater is a bit of a stretch to begin with and then having the expectation that you have enough heat to keep the windshield interior clear of condensation coming back over the Snoqualmie pass on a dark, cold, snowy night, well....

    Having to roll the windows down in a pretty severe snowstorm in order to keep the winshield defogged was not pleasing to my better half. Never happened again.

    Of course the TENSION involved in driving a rear engine rear drive car in those conditions probably contributed greatly to the level of moisture being accumulated in the cabin.
This discussion has been closed.