1997 Limited V6 Underhood Howling Noise

[U.G.N.]

Hi all,

I have got a howling noise since last September and need your help as Toyota dealership could not find out what is the cause of it. I have driven my vehicle for more than 6000 kms since I found out about the noise. I will try to describe it as much detailed as possible. The howling noise does not happen when the engine is cold (RPMs about 1100 or higher), when I just start the vehicle, I don't hear it. If I drive and the engine is warm, stop at a stop light, I could hear it with low RPMs (600 usually), it's the same monotonous noise like a flying bee. When I turn off the vehicle and start it again I hear the noise. It looks like the howling comes from the front (it's somewhere behind the driver's console in the middle) and it does not matter if the transmission is in Parking, Neutral or Driving position. The lower RPMs the louder howling noise. If I put engine above 1000 RPMs in Parking the noise disappears. Where could it come from? The dealership suggested change the whole transmission ($3800) or torque converter ($1100) but I believe the problem somewhere else. Thank you for your help!

[jetwhine]

U.G.N.,

When warm and at 600 rpm and you increase the rpm to 1000 does the buzz increase in pitch or does it stay the same? Does it get louder or does the sound remain the same as rpm is increased?

[U.G.N.]

Originally Posted by jetwhine

U.G.N.,

When warm and at 600 rpm and you increase the rpm to 1000 does the buzz increase in pitch or does it stay the same? Does it get louder or does the sound remain the same as rpm is increased?

Hi Jetwhine,

When the engine is warm and give it more RPMs (more than 1000) the noise goes away, it does not exist, the engine sounds as normal, I can hear howling only when the engine runs around 600-700 rounds.

[jetwhine]

U.G.N.,

Does the noise change before it goes away? In other words does it get louder or softer before it goes away?
Did you have any work done before the noise showed up? How many miles are on your rig?

[coontai]

fan clutch maybe?

[U.G.N.]

Originally Posted by jetwhine

U.G.N.,

Does the noise change before it goes away? In other words does it get louder or softer before it goes away?
Did you have any work done before the noise showed up? How many miles are on your rig?

I was listening to it and found that the noise changes tone (it's like if it would sing, from lower to higher tone). The pattern of the sound is the same, it does not get softer or louder, it's same howling noise, sometimes it gets louder.

What I also found that it does not necessary appear when I stop - it could disappear, I go for couple blocks, stop again and it reappears.

No work done before it has happened. I have about 301,500 kms right now.

[U.G.N.]

Originally Posted by coontai

fan clutch maybe?

Thank you coontai, did not know there is a fan clutch, thought of transmission clutch first

[jetwhine]

U.G.N.

Ok next question:
When the howl increases is it related to engine RPM or vehicle speed increase from a stop? So what I am getting at is it related to engine RPM increase or a Rolling increase from the tranny. Now I know that you have to give it RPM to get going but we have to eliminate the Engine RPM from vehicle movement from the tranny.

[U.G.N.]

Originally Posted by jetwhine

U.G.N.

Ok next question:
When the howl increases is it related to engine RPM or vehicle speed increase from a stop? So what I am getting at is it related to engine RPM increase or a Rolling increase from the tranny. Now I know that you have to give it RPM to get going but we have to eliminate the Engine RPM from vehicle movement from the tranny.

I did a test and it does not matter if I give more RPMs in Neutral or when I drive the vehicle, noise disappears with higher RPMs regardless movement or stop of the vehicle.

I see random behaviour in noise appearance - it could be in Parking or Driving mode but most of the time when engine is hot and run at lower RPMs but it is not the same. It's either louder or quieter and even feel some vibration sometimes when it's louder.

[jetwhine]

U.G.N.,

I'm thinking the same as coontai is thinking. It may be the fan clutch going bad on you.

[U.G.N.]

Thank you guys. What basic diagnostics I could do myself to find out the issue is in the fan clutch? If it has an issue I have no tools or capability to fix it myself and would need to bring it to a dealership or mechanic. Is it an easy diagnostics for them the check on the fan clutch? I'm planing Timing Belt replacement on coming week if it helps do the clutch as well.

[jetwhine]

U.G.N.

If you have the timing belt done make sure you have all shaft seals replaced and a new water pump. The sound you hear and describe sounds too me as though it is from the engine not the tranny. I could be wrong and sorry if I am but you are going to do the timing belt and if one of the components of the change is bad then your problem will go away. However since you are doing the job it would not hurt to change fan clutch at the same time. That would eliminate those items as a culprit. Good Luck.
Let us know what fixes it.