I have a question for all.

I have a 2003 G35 sedan with about 116000 miles. Always loved this car. I use full synthetic (Mobile 1 extended). Never had any major major problem with it. I do regular maintenance and care.

Recently, I am hearing a lot of highway noise. Literally it is loud to the extent that I can hear it with normal music playing. I noticed this less than 2 months ago. I know it is driving noise as when I am at a red light, it is VERY quiet. Very very quiet, no extra noise at all and smooth. In fact when I am at red light, sometimes I wonder if the engine is on or not. It is that smooth. But as soon as I step on the gas, I hear his *extra* noise, kind of humming or echoeing from somewhere.

I do not know if I need to be worried at this point . Woiuld appreciate if anyone can guide me as to where to start looking for this problem.

Thanks in advance.

-- Bajracharya

 

how are your tires?

Some roads in my area are just noisy, some roads are smooth and quiet

 

Not much of a description is offered but the engine is OK.
A mechanically experienced person is most likely needed to test drive your car and diagnose the extra noise. Hopefully it's tires.

If you choose, I suggest tires be tested by you while driving and you roll in "neutral" gear selection at 45 mph for at least 10 seconds per test.
This test unloads the drivetrain components for a few seconds from the noise source for the duration of the test. Find a long straight declining length of road for the car to maintain your test speed without slowing.

You will hear and feel differences that could lead you closer to the source of extra noise.

Be careful and safe. Good luck

 

The tires are not bad, may be 50% left on all 4. Installed Feb 2010 and around 17000 miles on them.

I will try the go to neutral test and see.

 

Baj, if the extra noise changes while "coasting" in neutral listen for 2 outcomes.
a. coasting in neutral the extra noise is noticeably reduced it leads to drive train components
b. re-shifting in to a gear after coasting and the extra noise returns it is more likely one of the drive train components.
c. next step is to have your differential gear oil level topped off and if you have a manual transmission have that gear oil topped off.

Heh, you should have "item c" lubes completed anyway. Regardless of how the "coasting" test results; if that low or empty gearbox is making friction it may well be what you feel is extra hum or noise. You have something to be concerned and want whoever changes those gear oils to report what they find when draining the old oil.

 

Tires can look fine but be trashed. Check for feathering of the tread or other unusual wear.

You should have a shop check all the bushing in the suspension. Replace any that need repair (I'm guessing your front end bushing are shot).

These cars aren't really known for road noise as much as tire roar. Just get the tires and suspension inspected and get back to us.

 

I am at 118000 miles and just got the 2 belts and the spark plugs changed last weekend. Still hearing some noise although the car is running much smoother now than compared to before. The "extra" noise is still there.

I haven't really been able to coast downhill in neutral as I am in South FL and everything is flat here, I mean really flat.

Will see after topping diff oil and take it to a good mechanic.

 

+1, check your compression rod bushing and other bushings. I used to have a squeaking from my passenger side, changed the compression rod bushing and it's gone. It could also be ball bearing if that humming noise is increasing at higher speed..

 

Check your wheel bearings

 

you have about 19k miles in your tires right? Maybe its time to check them? if you're dropped maybe you have excess camber wear? maybe a tire is going bald? maybe oyu need an alignment?