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At Road Atlanta, my 2019 Grand Sport M7 suffered some kind of oil leak that got onto the serpentine belt and flung oil all over the engine bay, causing a mess and a bunch of smoke. After cleaning and inspecting to the best of my ability, I cannot figure out where this oil came from.
I had a 1.5 hr drive home, and I stopped every 15-30 minutes to inspect the engine bay and the oil level. No change in either the whole way.
At home, a small amount of residual oil dripped onto some cardboard overnight, but nothing that couldn't be explained by just leftovers from the spray.
Suspecting that maybe the dry sump burped into the vent hose in the intake, I removed the intake tube. The air filter was dry and the tube and throttle body only had a small amount of residue, so no smoking gun there either.
Any ideas from you folks? It clearly came from the front of the engine, in a place where it could get onto the serpentine belt, but that's all I can deduce. No CEL, good oil pressure, otherwise running fine.
My assumption was motor oil- it was amber in color in the places it collected. Can a tensioner even fail in such kinetic manner? Also, if it failed, shouldn't I have noticed some other symptom?
Looks a little grody. I guess I'll clean it and see if any more fluid collects on it?
Just thinking out loud. I don't know what color the damping oil is in the belt tensioner. Most just mention the oil leak or a squeaking noise. I don't recall any threads mentioning oil all over the engine bay. But I can't envision a motor oil leak that burps a bit and stops...
Clutch fluid should not be in front of the engine and turns from amber to dark very quickly. You would certainly have noticed a brake leak - so what's left?
Maybe eyeball the oil drain plugs, filter, and oil cooler - but again I don't understand how these could leak and then stop.
Probably should check brake and clutch reservoirs to eliminate any questions...
The only other oily stuff would be the oil in the A/C system - but again, you would know if you lost A/C.
Front oil seal started to leak under track conditions and then stopped on normal driving home. (gentle driving). It does not take a lot of hot oil spray to cover everything in the engine compartment.
Last edited by Tinkertech; Jun 19, 2026 at 07:30 AM.
Front oil seal started to leak under track conditions and then stopped on normal driving home. (gentle driving). It does not take a lot of hot oil spray to cover everything in the engine compartment.
Ugh, I really don't want it to be the front main seal, but that possibility has been in the back of my mind. I guess I can check the pcv valve and do some aggressive driving.
Also notice that other thread mention a bit of oil contained in the alternator bearing right in the alley of this issue
After having intake manifold and tb swapped i smelt burning oil... took it back to shop and they determined it was the alternator. There is a coupler in there that failed and flung oil on hood / inner fender, but it was black in color, after swap of alternator and clean up, no smell
If I replace the main seal should I just order another OEM, or is there a worthwhile upgrade? Any point to replacing the balancer while it's off?
There are super duper balancers that cost $500 +, I'm not sure what they do. But, make sure when you remove the main bolt, you replace it. It's a one time use item.
Fel-Pro and BTR make front main seals, might be worth checking out.
If I replace the main seal should I just order another OEM, or is there a worthwhile upgrade? Any point to replacing the balancer while it's off?
You can use an LS3 seal as some of us who have blowers have done but front main seals do not just start leaking , if you determine that its the main seal , something caused preasure in the crank case ... check the PCV system , I had what I thought was a main seal leak ... turns out it was because I did not apply silicone the Harmonic balancer bolt after adding my blower pully
Checked all the vent lines to/from the engine, and replaced the pcv valve since the cost to do so was negligible. The valve was "loose" but not blocked, and I was able to blow air through all of the lines. I even checked the operation of the system by blowing some air into the crank case and witnessing the pvc valve and hose venting into the intake manifold. So- uh?
I took a borescope and looked in to the MSD intake manifold and did see some pooled oil in there. Is that normal, or a clue?
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Oil Spray In Engine Bay at the Track
