The engine sounds louder, now smelling burning oil after an hour of driving.

[MoneyJohn]

2006 Sentra, 1.8S (QG18DE engine) with 125K miles on the odometer.

In the past, we would not drive more than 3000 miles a year, but since August 2022, my wife started driving it to work, ~50 miles daily round trip.

For the last couple of months, she is complaining that the engine sounds louder, and now for the last week or so, she mentions a faint burning oil smell in the cabin after an hour of driving (At the end of every trip, never in the beginning). I immediately checked the oil level and it is fine. There is no change in how the car drives. There is no engine light. The oil was changed 3 weeks ago with Mobil 1 5W-30. The filter was hand-tightened. Never experienced oil burning before so can't say much. Her first half-hour drive is on the interstate and the rest half an hour is in bumper-to-bumper crawling city traffic.

I pulled out the PCV valve to check if it was busted. While it's dirty, with significant carbon build-up, it rattles. I tried cleaning unsuccessfully with a brake cleaner. Installed back and the engine sounds the same (louder). I have ordered a replacement PCV Valve. OEM was unavailable locally. I will replace it next weekend.

What else can I check, if anything, or time to call the mechanic?

Thanks in advance.

 

[Jackson_Slugger]

This isn't the SER SpecV is it?

 

[MoneyJohn]

This isn't the SER SpecV is it?

No. 1.8 lit QG18DE, S trim. Will update the post.

 

[PontiacHO]

Make sure PCV vent hose and/or oil cap is secure. Not sure how the air breather intake assembly is made but also ensure it’s secure.

 

[Jethro_Bob]

check the flex pipe on the exhaust, it could explain both issues. A google search shows the flex pipe as an assembly with the catalytic converter. Any muffler shop should be able to cut off the flex and weld in a new one.

 

[Oillover]

check the flex pipe on the exhaust, it could explain both issues. A google search shows the flex pipe as an assembly with the catalytic converter. Any muffler shop should be able to cut off the flex and weld in a new one.

+1
That was the problem on my 97 Escort and 07 Focus.
When inspecting it on the vehicle, the flex area will appear slightly blackened with small black dots in the cross-hatched mesh area.
That's when you know you have a flex pipe leak.

 

[Warstud]

The oil was changed 3 weeks ago with Mobil 1 5W-30.

1) Is 5w30 the correct grade ?
2) Have you ever used Mobil 5w30 in this car ?
3) Are you using a different Oil Filter than before ?

 

[carviewsonic]

Burning oil smell..
Check the trans fluid level as well, it could have a small leak onto the hot exhaust.

 

[MoneyJohn]

@Jethro_Bob @Oillover
If there is a flex pipe leak, wouldn't it throw a code?

 

[MoneyJohn]

1) Is 5w30 the correct grade ?
2) Have you ever used Mobil 5w30 in this car ?
3) Are you using a different Oil Filter than before ?

1. Yes
2. Yes
3. Yes, Usually I use a regular filter (6607), Now using an oversized (9688) filter. The next oil change is in Feb. I want to avoid going under the car during peak winter. So will leave the filter, and change the oil using an oil pump.

 

[MoneyJohn]

Burning oil smell..
Check the trans fluid level as well, it could have a small leak onto the hot exhaust.

Will do.

 

[Jethro_Bob]

@Jethro_Bob @Oillover
If there is a flex pipe leak, wouldn't it throw a code?

I have a love/hate relationship with s10's every one of them needed flex-pipes. None of them threw a code, it only takes a small leak for noise and exhaust smells to escape.

 

[hemitom]

Burning oil smell..
Check the trans fluid level as well, it could have a small leak onto the hot exhaust.

was thinking the same ! small oil leak dripping on hot exhaust.

 

[MParr]

I’m thinking that you have an issue with the exhaust. It needs to be checked from the exhaust manifold to the end.

 

[OVERKILL]

Check for seepage around the filter or a valve cover leak.

 

[Jetronic]

I’m thinking that you have an issue with the exhaust. It needs to be checked from the exhaust manifold to the end.

put a rag on the tailpipe with the engine running, you'll qyuickly know if there's a leak

 

[FZ1]

2006 Sentra, 1.8S (QG18DE engine) with 125K miles on the odometer.

In the past, we would not drive more than 3000 miles a year, but since August 2022, my wife started driving it to work, ~50 miles daily round trip.

For the last couple of months, she is complaining that the engine sounds louder, and now for the last week or so, she mentions a faint burning oil smell in the cabin after an hour of driving (At the end of every trip, never in the beginning). I immediately checked the oil level and it is fine. There is no change in how the car drives. There is no engine light. The oil was changed 3 weeks ago with Mobil 1 5W-30. The filter was hand-tightened. Never experienced oil burning before so can't say much. Her first half-hour drive is on the interstate and the rest half an hour is in bumper-to-bumper crawling city traffic.

I pulled out the PCV valve to check if it was busted. While it's dirty, with significant carbon build-up, it rattles. I tried cleaning unsuccessfully with a brake cleaner. Installed back and the engine sounds the same (louder). I have ordered a replacement PCV Valve. OEM was unavailable locally. I will replace it next weekend.

What else can I check, if anything, or time to call the mechanic?

Thanks in advance.

Perhaps the burning smell is coming from a slight oil leak that is burning off.

 

[Oillover]

@Jethro_Bob @Oillover
If there is a flex pipe leak, wouldn't it throw a code?

Nope
Neither of my Ford's threw a code. I don't think any other vehicles would either.
Like i said above, a careful inspection of the mesh area will indicate if there's a leak.
Given the age and mileage, this is most likely the cause of the noise.

 

[SatinSilver]

What brand filter is it? Kind of curious.

 

[Greasymechtech]

Didn't some years of the 1.8 eat head gaskets? I would send the oil out for analysis. There also shouldn't be any crud on the PCV valve.

I would run it thru a car wash, clean engine bay, check for rodent nests and engine trans leaks....

I would either using borescope or valve cover removal and inspect for sludge.

Without knowing the history of maintenance, or visual inspection competence, we're just guessing.

At this point, I hope that you have fresh coolant, newish transmission fluid, thermostat/radiator cap, serpentine belt, if not electric steering then a good PSF flush, plugs, scan for codes..... and research the model/engine issues on some of the sentra/nissan forums