Interrelated problems with fumes and maintenance light? 2005 Jeep Liberty Renegade

Maintenance/Repairs
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Hey guys, I am going to be taking my Liberty into my mechanic this week and wanted to know if anything I am going to list with my car seems to be issues connecting to each other, or things people have experienced and since alleviated.
Car has 200k mi. by the way, RWD, auto. transmission.
Love to know your opinions:

Oil maintenance light comes on every other couple times I start my car, but not every time, and stays on for the ride until I shut car off

Something smelling like burning under hood
Drove up a local grade recently, and after its hill on the straightaway, there was some smoke/fog coming inside cabin vent— opened windows and let it air out, eventually stopped 5min later, no lights or other signs of overheating, drove on for 30 minutes more just fine.

Also—Failed heater core? (Am OK with having bypass by the way👍)
Symptoms I have noticed:
Sweet burning smell in cabin
Fogged windshield
Smell of fumes when I crank fans
—>Heat DOES work, but using the fans system pumps in a lot of fumes— feels unsafe to use, I don’t use it. A/C is lacking a bit (using A/C specifically is no concern to me until summer season, I don’t desire a repair for that).
—>No leaking on mats though as noted by many forums online.

Car’s dash temp gauge is always stable, right in the middle.
RPMS idle at 600 and from 2000-3000 while driving :+1:
Occasional puff of (white) smoke from exhaust—not common or an everyday thing —But usually strong smell of exhaust/burning outside while car is running.

7pm of 3/5/23, reversing into the driveway, headlights showing smoke/steam from under hood.

My main concern: concerning fumes coming into cabin and strong exhaust, whatever that relates to, and triggered oil maintenance light.

Fluids all very recently serviced:
+rear differentials serviced
-oil change
-trans. fluid replaced (I think? Big Brand replaced the gasket and said the fluid came out with it and so they replaced/topped off its fluid.)
-new radiator
-new sparkplugs (all)
-new transmission gasket
-new neutral ignition safety switch
-new air cleaner to cylinder head hose

Only other maintenance I’m aware of are:
-due for serpentine belt
-brakes/rotors
-ball joint replacements? (squeaks over dips.)

Car actually drives really nicely, makes no noise of any struggling, smooth idle.

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Are you sure this is a maintenance light and not an oil pressure light?

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My mistake, yes, the oil pressure light.

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Oil pressure needs to be checked with an external gauge, if you are lucky it may just be a bad sending unit.

You need a new heater core. Your mechanic might be able to bypass your heater core, but in my opinion not a wise decision.
I don’t know the labor required to replace the core but expect $$$.

If exhaust smoke, possibly either or both, an exhaust manifold gasket leak, a broken exhaust manifold, or (if equipped) flex pipe.

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The buring oil smell is likely a leak putting oil on the exhaust. If your oil light is coming on Check Your Oil Level Right Now!! and add if low. If you can’t see oil on your dipstick the oil is VERY low and your engine is being damaged everytime you see the light.

If the level is OK, follow @Purebred 's advice. If the actual oil pressure is very low, the engine is worn out and needs replacing… or you need a new car since an egine replacement costs far more than this Jeep is worth.

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Why is it not wise to do a heater core bypass? My mechanic said he’s okay with a bypass but not a replacement. I wouldn’t replace the core because of the complexity and labor cost, and I am in SoCal and I rarely ever desire to use my heater.

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Just to add to the above, if your oil pressure switch is working ok, the oil pressure has to drop to about 5 PSI for the light to come on… When building engines a good rule of thumb (on older engines, newer engines may be more due to tighter tolerances) is you want at least 10 PSI for every 1000 RPMS to be safe, if your light is on and correct you are starving the bearings etc of oil and damaging the engine…

On the heater core side, on my Hot Rod the heater core is bypassed for multiple reasons and when the window starts to fog up it is a PITA to clear off with a rag while driving, soo that limits me from driving in those conditions… Speaking of clearing the windows off, anytime you turn on your front defroster the AC turn on to clear the fog (if equipped) so with the AC not working (I think you said yours doesn’t work) it takes longer to defog your windshield… And No mine didn’t come with AC… lol… At least that is the way it is in the Nashville area with our HIGH Humidity, may differ in low humidity areas…
So, it doesn’t hurt the vehicle to not have heat but it sure does make it very inconvenient and possibly unsafe…

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Is there a reason why this wouldn’t trigger the engine light to come on as well?
I do know the engine light is functional because the engine light popped on recently and I had that serviced and light turned off.

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It all depends if the HVAC module (unit) is monitored by the computer or not…

" The AC control module is the the brain of the whole system. This electronically controls the interior AC functions such as fan speed, temperature (heat), and which vents the air comes from as well as controlling the AC compressor and mechanical system ."

I have replaced a lot of HVAC units that didn’t turn the CEL on when it went bad, but that doesn’t mean a lot of them are monitored by the computer(s) especially on the newer models …

As far as yours, I don’t think so but I could be wrong about that… I’m sure someone will correct me if I am… lol

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@davesmopar This makes sense. I’m sorry, I meant more so about the PSI, and why an oil pressure light coming on would not also trigger the CEL light if there could be damage happening to the engine.

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The CEL is yellow… you can continue to drive but get it checked. If it is flashing, it means get it checked ASAP but you can drive a short distance.

The oil light is red because it means STOP NOW. There is no need for a CEL and the red oil light because RED means STOP! Ignore it at your financial peril.

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Oops, sorry I missed that one… But Mustangman said it perfectly…

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Being in So CA makes a difference, with the dryer air rarely any need for defrost/heater function.

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Here, sometimes just breathing will fog up the windows… :laughing:

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Good advice above. OP likely has more than one problem. IMO first priority is to check for exhaust system leak, could create health problems for occupants. Oil level/pressure is next priority. After that, since you can see smoke coming from engine compartment, ask your shop to open hood to see where exactly it is coming from. Maybe just a valve cover oil leak is dripping oil onto hot exhaust component. That will definitely create a lot of smoke and odor. Don’t defer on this. An exhaust system leak could create health hazards, and oil leak could cause engine fire.

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@Mustangman Thanks for the insight on urgency.
I went ahead and checked my oil level even though I just got an oil change 2 or 3 weeks ago, and my oil level was a little low. I added 1.5 qts and that red oil light went away.
Turned on my car a few times since I topped it off and the light has stayed off, luckily, since I needed to be places today.
This does indicate I have a leak though in the least. Otherwise my dash is clear now and I just need to have the exhaust smell checked out by my mechanic, which can be several things as mentioned by someone above, plus that heater bypass.
I’ll have to update after I get the car serviced, and I’ll add what was needed in case someone else might benefit from this thread.

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Thanks so much, I’ll be bringing in the car for that exhaust leak this week!

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You should never let the car get more than 1/2 quart low. Check it at least weekly. You don’t post how many miles you drive a week but if you have to add more than a quart every 600 miles, start saving for a new car.

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