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Discussion Starter · #1 ·
Hello! Two days ago I noticed an unusual noise coming from under the hood of my 2004 Highlander (100,070 miles, 6Cyl 3.3L MCU23L-BRANKA). It sounds kind of like the whirring sound of propellers from a drone or rc plane. I popped the hood last night and took a video of the sound. It gets louder when the engine is revved. I tried unplugging the alternator while it was running but that didn't seem to stop the noise. Any ideas of what it could be? Video here: 2004 Toyota Highlander Noise/Sound

Thanks for your help
 

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Any warning lights on?
Does it change with AC on/off? Is your AC working? Check for bubbles in the AC sight glass at 1500 RPM after the AC has been on a few minutes.
Does it change when headlights, blowers and defoggers are on?
Does it change when you turn the wheels while stationary?
Is your power steering reservoir full?

You should be able to narrow down the location with a stethoscope or just a piece of tubing. A cheap tool that ctually works really well.
Obviously, watch out for the belts and fans.
When was the timing belt changed? Was the full kit installed? Was it a Toyota or AISIN kit?
I have my opinion about what it is, but try to diagnose it rather than shot-gun it.
 

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Discussion Starter · #4 ·
Any warning lights on?
Does it change with AC on/off? Is your AC working? Check for bubbles in the AC sight glass at 1500 RPM after the AC has been on a few minutes.
Does it change when headlights, blowers and defoggers are on?
Does it change when you turn the wheels while stationary?
Is your power steering reservoir full?

You should be able to narrow down the location with a stethoscope or just a piece of tubing. A cheap tool that ctually works really well.
Obviously, watch out for the belts and fans.
When was the timing belt changed? Was the full kit installed? Was it a Toyota or AISIN kit?
I have my opinion about what it is, but try to diagnose it rather than shot-gun it.
Thanks C R. You will have to forgive me for being a non-car guy, so please be kind when you read #7.

1. No warning lights.
2. Occurs with A/C on and with A/C off.
3. A/C is working (had a shop replace the A/C compressor, condenser, and belt in June 2019)
4. I have no idea where the AC sight glass is. I did a quick Google search to try to find out where to look but didn't find anything helpful. Can you please tell me where this is just for my own knowledge?
5. No change with headlights, blowers, defoggers.
6. Gets much louder when turning the wheels while stationary.
7. Here it is: Power steering reservoir is empty.
8. Haven't ever changed the timing belt.

So...a few follow-up questions: I can obviously go purchase and refill the power steering fluid, but is it common for this fluid to be used up over time? Or does it only go down if there's a leak somewhere?

If I need do need to take the vehicle to a mechanic to fix a leak, should I have him do the timing belt and spark plugs at the same time, since I've never had those things done? Is it advisable to go to a Toyota dealership for the work, or the shop down the road that I have used for work in the past (the A/C stuff)?

Thanks again!
 

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Thanks C R. You will have to forgive me for being a non-car guy, so please be kind when you read #7.

1. No warning lights.
2. Occurs with A/C on and with A/C off.
3. A/C is working (had a shop replace the A/C compressor, condenser, and belt in June 2019)
4. I have no idea where the AC sight glass is. I did a quick Google search to try to find out where to look but didn't find anything helpful. Can you please tell me where this is just for my own knowledge?
5. No change with headlights, blowers, defoggers.
6. Gets much louder when turning the wheels while stationary.
7. Here it is: Power steering reservoir is empty.
8. Haven't ever changed the timing belt.

So...a few follow-up questions: I can obviously go purchase and refill the power steering fluid, but is it common for this fluid to be used up over time? Or does it only go down if there's a leak somewhere?

If I need do need to take the vehicle to a mechanic to fix a leak, should I have him do the timing belt and spark plugs at the same time, since I've never had those things done? Is it advisable to go to a Toyota dealership for the work, or the shop down the road that I have used for work in the past (the A/C stuff)?

Thanks again!
DC,
Yeah, this forum is for learning.
First things first - the power steering:
One of the weaknesses of the Gen 1 is in the power steering lines, especially in corrosion country.
You probably had a slow leak. If you search the forum, you will see it is fairly common.
Best solution - have it towed to a good shop for inspection and recovery.
I would still get some Dexron III transmission fluid and fill the reservoir. I would try to get some fluid into the system by gravity by turning the steering wheel lock to lock a couple of times with the engine off. That way, if someone starts the car during the tow process, at least now you have fluid. Not good for the tires to turn without rolling, but we are talking relative issues here.
If the tow and professional inspection is not a option for you, after filling the reservoir, bleed the system by turning it lock to lock twice, and refill, repeat until the fluid level does not change.
You could pull the belt off and spin the pump by hand a few times to try to get some fluid in it, but if you are not comfortable with working on the car, that is not something I would start with.

Some relevant threads attached.









 

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Next thing, the timing belt.
Timing belt service is recommended at 90,000 miles, and generally 6 years though the OEM belts seem to go 12 years and longer. There are stories of the OEM belt failing, but not many.
If the timing belt breaks, it can cause engine damage.
I recommend getting it done. It is expensive, so shop around to an independent who will use the AISIN kit.

Relevant threads below:







 

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Third thing - AC sight glass. Not quite as easy to interpret as it was in the R-12 refrigerant days, but still useful.
It is tucked in on the “frame” rail next to the alternator near the ABS valve body and the windshield washer reservoir on the passenger side. You will probably need to wipe the glass to see. With the engine OFF.
The first step is to make sure your AC is working- the air from the center vent should be at least 35 degrees F below outside ambient.
Automotive tire Motor vehicle Automotive exterior Automotive fuel system Electrical wiring

Conditions to check the sight glass are:
Engine normal temperature with AC on for at least several minutes.
Engine 1500 RPM
AC on maximum cold and high blower speed with doors open. (Yep)
Compressor clutch engaged / compressor running

There can be some variation on very hot days, but If the refrigerant charge is good, you will not see many bubbles except as the compressor cycles off.
If you see no bubbles, it may either be empty or over-charged. You can tell which based on how the AC is working in step 1.
Insufficient refrigerant will reduce lubrication and can cause compressor failure.
This is a screening check that can be done easily by owner. However to see the true condition of the refrigerant charge requires a gauge set and thermometer.
 

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I’ve had my power steering system empty from changing the aforementioned steel return line before and just filled it up and turned the key. The pump was a bit noisy for a couple of seconds, but it didn’t seem to harm anything, as I’ve driven it over a hundred thousand miles since.
There are some diy methods that will permanently fix that problem. After mine rusted a second time I bought a length of nicopp brake line and bent it to fit, then installed it with hose clamps to the rubber hoses on either end.
Others will post their fix, I’m sure.
 
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