vpalacio

I'd like some help/feedback/comment on a potential problem I've noticed:

I have noticed for some quite some time that when the engine has been running a while or when using the air-conditioner, there comes a loud roaring from the car (from under the hood).

I assumed it was just the fact that I was driving a V8 enigne that the fan would sound soo loud. But recently while driving I noticed the loud roar and at that same moment needed to floor my gas pedal to gain momentum but found that I couldn't and the acceleration I needed wasn't there. This only seems to happen when the loud roaring is present.

This past week I had my car sent in for an oil change and to replace a transmission seal. (the phenomena described above was apparent before the service). I described the load roaring to my service associate @ Lexus and told me that they couldn't find anything to explain the load roaring. He attributed it to the engine fan spinning to cool down the V8 engine.

I am curious: have other GX470 drivers experienced this load roaring? It's pretty apparent especially with the windows closed and the AC running.

Should I visit another Lexus Service center to get a second opinion? I should add that I've never had a V8 car before my GX.

Any help would be appreciated.

gsobol

Loud roar is common on the GX especially when it's hot outside. Yes it's the fan. Hot temperature can reduce the available power, but not to the point when you can't accelerate. If you took your GX to Lexus of Rockville Centre, I WOULD look for a second opinion! And don't go to Lexus of Massapequa either - same incompetent management. Good luck.

brickauto

Here's my understanding of the engine fan. Firstly it's a mechanical fan so it always spins with the engine, however it has a clutch on it that allows it to spin slower than the engine when running without much load. When the engine load is high and require additional cooling (e.g. hot ambient temps, A/C on, coolant temp high) then the fan clutch engages and the fan spins faster thus creating the "roar" you hear.

I can hear the fan roar in my GX cabin when the A/C is on and the ambient temps are high or when I restart the engine after a short period of time from shutdown on a hot sunny day.

vpalacio

Thanks for the follow up posts.

I feel better knowing that the loud fan roar is a common thing with the GX.

However, the lack of power part annoys me, actually it makes me mad
I could floor the pedal while the fan is roaring and there would be no significant acceleration. Don't get me wrong, the car is moving, but not as responsive as I want it to be at that very moment.

I don't know much about engines but if I'm driving a V8, I dont think I should be at the mercy of a fan...

I have a history with Lexus of Manhattan so I will try to take my GX there for a second opinion.

gsobol

The fan can rob your engine off approx 10-25 horses when fully engaged. There is a clutch mechanism on the fan that acts on temperature (just like bi-metal). When the temperature is cooler under the hood, the clutch slips and the fan rotates slower. Because of the fan's inertia and the slippage of the clutch, the fan's RPMs are relatively low and constant and not directly related to the engine's RPMs, hence no roar. When it's hot under the hood, the clutch is fully engaged the fan's RPMs are directly related to the engine RPMs. As the RPMs of the engine are climbing up so are the RPMs of the fan, hence the loud roar.

There is another problem. Remember, our GXs are drive by wire. What that means is that your gas pedal is not directly connected to the engine. It's connected to the engine's computer, and the computer makes a decision on what to do - downshift and deliver more air and fuel to the engine, and how much. You can try this: when you experience the loud fan noise and apparent lack of power (I'm assuming this happens on the highway around 60-70mph), try downshifting to 3rd and flooring it. When you downshift by hand, you will force the engine to higher RPM level manually, throwing off what the computer elects to do and forcing it into higher power band, essentially overriding it a bit (can't override it all together, but this may help to troubleshoot your problem). It may be a computer glitch, sensor or actuator problem - possibly. This test would give you more info, and maybe steer the dealer into a possible solution.

As a side note, I'm disgusted with Lexus of Rockville Centre. They only care about their bottom line. The only thing I'll ever do there is change my oil, since I have it all paid up in advance. Let me know how you make out at the Lexus of Manhattan. I need to find a better dealer. Thanks.

vpalacio

Thanks for the breakdown about the fan. It makes alot more sense to me now.

One thing that I will add is that the lack of power for me happens on "Stop-and-go" traffic - less than 30 miles per hour - when the fan is roaring.

I have always had reservations about sticking to one Lexus dealership for all my service needs. I like Lexus of Manhattan but if you are not a repeat customer or purchased a vehicle from them they to tend treat you like a bastard step-child.

I have sat many a time up at the waiting room at Lexus of RVC and have heard my share of disgruntled customers venting their anger at their service reps.

brent0226

When then fan is roaring and you really need the power to accelerate, try just simply turning off the A/C until you're done accelerating. I may be wrong, but I don't think it's the engine coolant that is getting too hot; it's the hot refrigerant in the A/C condenser. There's a small electric fan in front of the condenser that usually runs with the A/C on, but when the car has been idling or sitting in very hot conditions, there is not enough air flow to carry away the heat from the A/C condenser, so the extra fan comes on to provide that extra air flow.

Basically in order to keep you cool, your car is extracting heat from inside the cabin and dumping it through the A/C condenser in the front of the car; there needs to be air flow to carry this heat away.

gsobol

Turning the A/C off will not turn off the auxiliary fan immediately. The computer will keep the fan on until the refrigerant is cooled. Also flooring the gas pedal will automatically turn off A/C compressor, as the computer will turn it off to maximize the power output to the wheels. Also the clutch on the mechanical fan reacts to the ambient temperature under the hood. But because it sits very close to the radiator, the radiators heat affects it the most.

Hmm, you experience the loss of power in the stop and go traffic. I haven't experienced it with my '06. True, the car is heavy and when it's hot outside the fan does roar, but I can't say that I ever experienced any problem when trying to accelerate from a stand still. I did couple of the - ever so exciting - Southern State merges yesterday from stand still (we had what 90-95 yesterday), and loud roar, but no problems with acceleration. Bottom line, you need to have it check out.

Pearlpower

iTrader: (2)

The fan clutch is common and robs a little of the HP from the engine. I notice it very seldom in our GX even with 100 degree desert heat where we live at 4k altitude. The GX still gets up and moves pretty good from a start. Much better than my SC. If you feel your fan is on too much I would have the fan clutch checked out as it is a temperature controlled clutch and not a centrifugal unit so the thermostat perhaps may be defective.
You can also check it out when the engine is nice and cool (off) and try to free spin it. The fan should move pretty easily as the clutch should not be engaged. Again-cool and engine off.

The G Man

Thats the problem with the older non-vvi-t engines, with the cooling fan on and AC on and what ever else, you are almost down to 200 HP. 200 HP for a 5000 lb truck is not going to accelarate fast. Even with the vvi-t engine, it gets loaded down sometimes. Sounds like there may be some transmission lagging issue here too, try disconnecting the battery for 30 mins to reset the shift pattern.

Cfcorrer

I had this problem just recently on my 2008 Lexus GX 470. It has been intermittent for quite a while but for the last week it never stopped.
I went to O'riley Auto parts and they had a new clutch for me in 2 hours.
Replaced it in less than an hour... really simple and...
NO MORE ROARING!

abaadi

Hi there, I am the other person who is facing the same issue with LX 470 V8. I am now bearing this since 8 months. We r in the gulf country which is quite hot and the car engine roars for sure. I have changed the fan clutch 3 times. The acceleration was very poor. Last week I was in a local garage who checked the noise n explained that the clutch is fine but why it's engaged because of the heating of the engine. It's not getting enough cool temperature. Imagine he went through the small part which I wouldn't think abt that was the thermostat. I got changed this just for 15 $ n the clutch was very calm the acceleration was perfect. He advised me if in case still the noise exists then we have to chk the water pump and radiator as well.
But as of now it's fine for me.

chiph9

Yes, the thermostat will eventually wear out. It's a good idea to change it when you do the timing belt service at 90,000 miles / 144,000 km

You should also verify that you are using original Toyota coolant. We get a 50/50 mix here - Dubai might have a different mix, or need a custom mix, so read the instructions on the bottle! Sometimes people will use 100% water in the radiator and that isn't as effective for cooling the engine.

Chip H.

Lexus4321

If the fan clutch unit is not an OEM part, then always get the largest fan clutch you can (look at the specs before buying).
I did upgrade my OEM fan blade to (I think) the new/improved AISIN one, which is a tad lighter and quieter than the OEM version.

Noise can also come from the various rollers of serp belt or the timing belt.