So I just bought my 04 G35 sedan. it has 179k miles - but has all service history from dealership and runs great!

Plus I only paid 7k

Anyways, it sounds like a jet or 18 wheeler under the hood when I am driving with the AC on. Granted, it is 100 degrees in Alabama ... but are these cars supposed to be this loud with AC on?

Is something wrong?

FWIW - in the mornings when it's cooler, I drive with the windows down and AC off and it is quiet.

Any suggestions?

Thanks!

 

there is definitely something wrong. it's been 100+ and super humid this past week in mid Michigan and i've been running the AC on max the whole time without a noticeable increase in sound from the engine bay let alone a jet sound. There is probably something wrong with your AC compressor or one of your belts. I would have somebody look at it though before I spent money on parts.

I have a 2004 g35x

 

i have the exact same problem with my 04.5X. I turn the ac on and after about 5 minutes of driving, the engine is very loud when i rev. I can then turn the ac off and again after about 5 minutes of driving the sounds begins to reduce. I have no idea what this could be.

 

WOW.. I would of sold you my modded 04 GX with 90k for 8.5k...

 

check to make sure there isnt too much freon in the AC system...the added pressure can make things sound funny

 

Sounds like possibly a bad bearing. Definitely have it checked out.

 

I should clarify that the sound is RPM dependent and not speed dependent. Cruising at 100 is normal, but revving in park is much louder with the AC on. There is also a vibrational quality that is transmitted throughout the cabin.

 

take a long piece of hose like 1/4 or 3/8 and use it like a stethoscope while somebody revs your car......youll hear where the noice is coming from rather fast.......

 

Sometimes extreme heat and humidity can do things to cars. This past week with temps over 100 regularly my A/C was making a funny noise similar to yours after 2500 RPM, but only on short around town drives. I've never heard that noise before and always use my A/C. This week, now that temps are lower, the noise is gone. It's something I will keep an eye on, but I am attributing it to the extreme temps.

If yours is constant even with temps somewhat back to normal, definitely have it checked out.

 

My car has always done this...it is normal. It is the fan for the ac. It turns off and on.