Engine noise inside the cabin sounds like a diesel


I have a 2004 G35 that has not given me many mechanical problems. However, before my last oil change, I noticed noise from my engine which I wasnt used to. After 2 days I checked the dipstick and there was almost no oil on it which greatly worried me. I put in two 10W30 bottles and got a normal oil change the next day. Its been a week now and I still hear this noise when I start my car and its idling (cant hear it while driving cuz of the normal engine/road noise). It almost sounds like a noise I would hear from my dad old 70s diesel benz’s, just not as loud. Its def mechanical but I can’t figure out what it is or where exactly its coming from. Its been 10 days now since the noise first started and it doesn’t seem to be going away. I just checked engine oil levels now and they are near max. When I open up the hood, I don’t hear the noise ( over the normal engine/belt noise), but its very apparent once inside the car with the doors closed and windows up.
I am worried my car might end up and die on me all of a sudden while on the freeway or if my transmission is going to go bad. Any ideas or suggestions would be helpful at this point before I take it in to a shop to get checked out.

Can’t say for certain, but the low oil condition may have caused some internal bearing/rod/piston damage. And that extra slack is now causing this knocking or clicking sound you are apparently hearing. What I’d do if my car probably is get out a length of garden hose and use it as a stethoscope to try to identify where the noise is coming from. Upper part of the engine or lower, front or back, etc. You may find it isn’t coming from the engine but from an accessory. You have to be very careful of course when working near a running engine. If you’ve never done something like that, or not familiar with the needed safety precautions, best to ask your mechanic to do it.

Rattles could be due to valve train lash, worn crankshaft bearings, or a worn timing chain/tensioner; or maybe a combination of all of those. Running an engine chronically low on oil will damage everything in that motor.

Offhand, it sounds like you’re not in the habit of inspecting the oil level on a regular basis and simply relying on the level being sufficient from one oil change to the next. If so, that’s not a good idea even on a brand new car in which oil consumption is known for a fact not to exist.

I am guilty of not checking the oil levels regularly. So from my limited understanding, valve lash wont be catastrophic but will cause bad fuel consumption. On the other hand I def wouldn’t want a worn crankshaft, and even if its just the bearings causing the noise, it might be a good idea to have the crankshaft inspected too? Would check oil pressure be the first good step to see if its indeed that before having to pay for taking out the engine? And if its the timing chain, then I guess i could seize my engine if it becomes too loose or breaks.
I think a trip to a shop is overdue now. Thanks for the help

Excessive valve lash will not cause much of a loss in fuel consumption. The main problems with that are the irritating rattle and the fact that it’s very tough on the valve train components.

An oil pressure test and compression test could reveal if there is any excessive crankshaft bearing wear and piston ring wear.
Timing chain rattle is pretty much an audible thing with no test for that other than digging into the motor a bit and noting if the chain is a bit sloppy.

Sorry I can’t be of more help but without actually hearing the rattle it’s near impossible to be precise and I do think that having a shop make a determination is the first step.
The problem with timing chain rattles is that it may often be only one bad sign in a problem engine because if the chain and tensioner is worn due to lack of oil that generally means other things are worn also. Best of luck.

So I somewhat lucked out with my car. Took it to a Nissan specialist and they found out the source of the noise was in fact a bad fuel damper. They replaced that and the cabin noise went down basically to what it was at before.
They did say that there is a leak/seeping from the valve covers but its minimal and shouldn’t cause any problems in the short-term.

Hey MoeAley,

I am having a similar issue with my Q50. I was just wondering if you replaced the fuel regulator or did you also have the hose replaced as well?
Here’s a link to the part i was looking at: Can you please take a quick look and let me know if I’m on the right track? Thank you for your time.


This is a 4 year old thread , you would be better served by starting your own with the info about your vehicle and problems. Also not a good idea to post what appears to be your VIN on an open web site.

Volvo V70,

Youre right, Thanks.