Engine/Transmission (1998.5 - 2002) Strange engine sound???????

[FNilo]

I was driving down the expressway going around 70 mph (2400 rpm) with the air conditioning on when there was a strange noise coming from the engine. It is kind of hard to explain but I will give it a try. It is louder and separate from the normal drone of the engine, kind of like the engine is increasing RMP's but it isn't. By decreasing RPM's, it doesn't change the sound or pitch that much. It will last for about 20 to 30 seconds and then goes away. It has only accrued about three or four times and does not effect the performance if the engine. (i. e. loss of power ) Coolant temp. is about 190 - 200 deg. (normal operating temp. ) It almost sounds like a large fan is turning on and then it goes away. It has only accrued when the air is on. Could it be the air conditioning compressor? I have ran the air many other times while city driving without a sound.



Any suggestions would be helpful.



Thanks,



Frank

 

[lmills]

If outsides temps are high and you are cruising with the A/C on it might be the fan clutch locking up. The fan is rather large and makes a lot of noise when it engages.

 

[FNilo]

Sounds right. Thanks for the help. I feel kind of silly now for asking



Thanks again.



Frank

 

[lmills]

They are rather loud and obnoxious when they lock up. The first time I heard mine it made me wonder also.

 

[KenHokie]

Yup, it sounds like the fan engaging and disengaging. The first time it happened on my truck, I was starting to worry about the noise until I remember reading a post about the fan "sounding like a turbo jet engine under the hood".