Been getting these spots under my 03 lately. The picture was taken from roughly where the driver seat would be.

Would I be correct in assuming it’s possibly a bad oil pan gasket? I’ve noticed a “hot” smell lately too (not a burning rubber or antifreeze smell). Could that be the synthetic oil burning off on the hot engine?

Thanks

 

Could be an oil pan, front or rear main seal. The oil pressure sensor fails more often and it more likely to be a problem. You have to take a look underneath the car and see where it is coming from. It's not that easy, but from the back of the intake manifold you can see the top of the block where the oil sensor is. You may be able to see if its wet. I used a cheap borescope from Amazon to find my oil leak.

 

Looks like a bad rear main seal. mine had the exact same pattern. the burning smell is from the oil getting onto the exhaust, especially after hard pulls. i also had a upper oil pan leak. replaced both of those gaskets over a year ago and my pan has been bone dry since. i would check your oil pressure sensor and cam sensor first though as the rear main and oil pan is not an easy or cheap fix on these cars.

 

I was afraid it would be a main seal, LOL.

Any idea (ball park) what it would cost to fix?

 

Probably north of $1k if you do just a rear main seal. but if you do a rear main it’s also a good time to do a clutch so the cost could stack even higher…

 

You need to lift the car and clean the engine as good as you can then drop it down and drive it a few miles then lift it again and try to see where it's leaking. A simple leaking PCV hose for example can appear as a more serious problem after the wind blows the oil all over the pan and exhaust.

 

Replace your PCV.

 

I have a friend with an 04 A4 coupe.. It was hemorrhaging oil from every seal! I looked it over and someone put the wrong PVC rubber hose on the TB to Valve Valley cover fitting. The hose crimped over and the engine was building up crankcase pressure when running. Remove your oil fill cap with the engine idling and insure there is a very slight SUCTION at the oil fill spout. Make sure your PCV pluming is working and not leaking vacuum.
I had a front timing chain cover dampener seal go bad. (They get hard and cut a grove into the dampener sealing surface) I had engine oil from the front of the engine to the differential. Talk about smell and SMOKE! WHEW!

Here are several things I recommend doing> As FAST one & C5MSG2004Vert stated, get under the car, CLEAN IT Brake parts cleaner and some rags/shop towels will get it clean and dry!, Then drive it a short distance and fix what is leaking. If you don't pin point the leaks, you can guess/speculate all day.

Add a quality seal swell additive to a fresh oil change. If the seals are a little hard & worn, it will allow them to soften and seal the leak.

If you actually do have a pan to block leak, Re torque the UPPER oil pan to block bolts. They have been known to loosen and allow oil to leak out.
NOTE-1 CAUTION! The rear two M6 pan bolts that screw into the rear cover STRIP VERY EASY! Only snug those up lightly!!! If you have a removable lower bat wing cover on the bottom of the oil pan, those little screws strip out easily also. 106 INCH POUNDSis the spec ! I wouldn't go much over 50 in/lbs. Especially if the screw threads are oil contaminated.

The Oil filter/oil temp housing on the side of the block can also leak. .

Yep, That Oil Pressure Sensor on the back of the block is a very common leak issue! Get a flashlight and an inspection mirror and inspect it for leaking oil. It leaks out of the body of the sensor.

Give it a good cleaning and inspection.

BC

 

OK so I have seen advice (in this thread and also from some friends of mine) on adding a good oil stop leak product (Lucas, in particular) and see if that helps.

I’ve kept an eye on the oil level and it’s not moving much, so the leaks can’t be that bad. Oil level is currently just a little bit below the midpoint on the dipstick so that means it’s got the required 6.5 quarts.

Adding a quart of Lucas would obviously bring the overall level to 7.5 quarts.

Is that too much for normal driving?

 

From the few spots on the ground, we know you don't have a GUSHER LEAK. IMHO, I would clean the bottom of that engine, cradle and bell housing to actually pin down and correct the cause of the seep.

 

Would not add any of those magic healing potions to my oil. If the gaskets are leaking that bad just get them replaced. Might be a little money but better investment. Yes 7.5 quarts is way too much.

 

Aren't all Chevy's and Harleys supposed to leave their mark

All the usual suspects have been mentioned already. You didn't mention your mileage but, add valve cover gaskets to your list of inspection items. If you can smell a whiff of burning oil, it means its contact exhaust. Small leaks are sometimes hard to track down as oil is a viscous substance that like to move about freely

 

137k miles

 

At that mileage, could be anything or everything lol. Here is what I would do. Drive the car up to operating temp...take a nice drive...park...then get it up on some jack stands. Look under and if you cant find anything obvious...Clean the underside area of any oil and let it sit overnight. Any leaks that are going to re-appear...will do so as the engine cools. As was noted above, that is a baby leak. Annoying if you have a nice driveway or garage. In the meantime cut up one of the wifes big Amazon boxes and slide it in the area where you park over. Problem temporarily solved of marking your garage floor.

 

Right on, Bill. I was talking about oil leaks to a very good performance/tuning shop here in Michigan recently. They mostly work on LS/LT engines. He said that the vast majority of oil leaks he sees on on these engines is caused by improper/bypassed PCV systems, or pinched vent tubes on cars guys have removed the OEM PCV system. Any engine will pressurize the crankcase without sufficient venting or a functioning PCV system.....