Sudden oil leak on recently rebuilt engine

[MorrisOnTheGo]

Last Thursday night, while driving back home, I crested a mountain pass at about 4,400 elevation after about 2,000 foot climb. I had not pushed the truck hard on the uphill portion, but did down shift to 3rd and maintained about 60 to 65mph. I was coasting down the opposite side of the mountain on the freeway when after about 3 or 4 miles on the down hill side, my check engine light came on, and I saw that my oil pressure gauge was reading zero. I immediately pulled over and shut down the engine. When I checked under the hood, the dipstick showed no oil, and I could see that the engine compartment was covered in oil that was dripping to the ground in many locations, so I could not pinpoint where the oil leak was coming from. I got the truck towed home (expensive tow for only about 55 miles, but it was almost midnight by the time he got to me). I checked the truck the next day to verify that the drain plug and oil filter were still in place, and looked around during the daylight, but still can't figure out where the oil leak is coming from. Not being very knowledgeable about V8 engines, I'm hoping that one of you reading this can point me in the most likely direction, on where this catastrophic oil leak might be coming from. It does not appear to be leaking from the valve covers, or head gasket, and is probably coming from somewhere lower on the engine, and most likely on the drivers side of the engine compartment, not the passengers side, but there is oil everywhere. Any and all advice will be greatly appreciated, as I would like to diagnose this leak before I tow the truck a 2nd time to the mechanic who installed my 383 stroker rebuilt engine.

 

[Road Trip]

Last Thursday night, while driving back home, I crested a mountain pass at about 4,400 elevation after about 2,000 foot climb. I had not pushed the truck hard on the uphill portion, but did down shift to 3rd and maintained about 60 to 65mph. I was coasting down the opposite side of the mountain on the freeway when after about 3 or 4 miles on the down hill side, my check engine light came on, and I saw that my oil pressure gauge was reading zero. I immediately pulled over and shut down the engine. When I checked under the hood, the dipstick showed no oil, and I could see that the engine compartment was covered in oil that was dripping to the ground in many locations, so I could not pinpoint where the oil leak was coming from. I got the truck towed home (expensive tow for only about 55 miles, but it was almost midnight by the time he got to me). I checked the truck the next day to verify that the drain plug and oil filter were still in place, and looked around during the daylight, but still can't figure out where the oil leak is coming from. Not being very knowledgeable about V8 engines, I'm hoping that one of you reading this can point me in the most likely direction, on where this catastrophic oil leak might be coming from. It does not appear to be leaking from the valve covers, or head gasket, and is probably coming from somewhere lower on the engine, and most likely on the drivers side of the engine compartment, not the passengers side, but there is oil everywhere. Any and all advice will be greatly appreciated, as I would like to diagnose this leak before I tow the truck a 2nd time to the mechanic who installed my 383 stroker rebuilt engine.

Greetings MorrisOnTheGo,

Sorry to hear about you being put on the side of the road with a showstopper like that.

In order to go from generic to (more helpful) specific replies, could you please tell us
the specifics about your truck and it's powertrain? (ex: I drive a '99 C2500/454/4L80-E/etc)

Generically speaking, there are two types of oil leaks in our engine bays:

* Unpressurized (weeps/seeps/leaks at stationary gaskets or seals on rotating surfaces)
* Pressurized: Engine oil cooler line failure at fitting or corrosion, oil pressure sensor
loose or failed, drilled oil passageway plug, etc.

Leak history is important, and can help you figure out what you are facing much quicker.
Has there been a long history of a slow leak that has dirtied the engine bay over time?

Or was the engine bay clean & leak-free until a sudden oiling event occurred, and nearly
all of the engine bay was involved?

NOTE: I have helped others troubleshoot a sudden oil leak, and it turned out that the
last time they added oil they were interrupted and the fill cap wasn't replaced? Or it
was replaced, but it wasn't installed securely and rattled off?

If the fill cap is still present, but this leak was both large and sudden, IF you have the
engine oil cooling option, then perform a careful visual check of those external
pressurized lines.

NOTE: Posting clear pictures of the problem will allow the talent in here to help narrow
down where the leak originated & how to resolve it.

Best of luck --

 

[GoToGuy]

Always start with Year, make , model, eng. We can't see it, they look the same until you open the doors and hood. Newly installed , new engine ? Obvious ones , did filter come loose? Filter gasket seal? Probably not.
You said oil all over engine bay? First guess, oil cooler lines or line attachment fittings. Did you install new oil cooler lines?
Through 4 quarts in it , I'd spin it over with spark plugs removed , just enough to see where it's leaking if it isn't obvious. ( Like oil cooler lines rubber part blown out.). Or the crap connect fittings, at filter boss.

 

[DerekTheGreat]

Oil all over eh? Any photos? Sounds like one of your connecting rods decided to have an abortion.

 

[WICruiser-97]

If you have an external oil cooler check the lines that run from the filter area to the cooler in the front. If one of them developed a crack the oil pump would spray oil all over until there was no more left to pump.

 

[Road Trip]

...I checked the truck the next day to verify that the drain plug and oil filter were still in place, and looked around during the daylight, but still can't figure out where the oil leak is coming from.

...It does not appear to be leaking from the valve covers, or head gasket, and is probably coming from somewhere lower on the engine, and most likely on the drivers side of the engine compartment, not the passengers side, but there is oil everywhere.

I was reading GoToGuy's comments, and it reminded me of another way that an otherwise
healthy engine can suddenly develop a serious oil leak. You mentioned the engine was
recently rebuilt? Was the engine oil & filter replaced a 2nd time shortly after it was first
fired up?

If so, there's the possibility that the original oil filter left it's circular gasket behind, the
mechanic didn't see this, and then installed the 2nd oil filter (with it's own gasket) on top the old
one that was left behind?

Sounds crazy, but the double gasket thing will usually cause a huge leak immediately, but
every so often it will work for awhile, only to fail when you are out on the road. (I've been
fortunate, for it only happened to me once, it failed immediately, and ever since I make
absolutely sure that the old filter didn't leave it's seal behind on the block mounting surface.
See attached.)

If the oil filter installation is good, then based upon your description the lower driver's side
of the engine would coincide with where the engine oil cooler lines reside. I'm chiming in on
GoToGuy's double oil filter gasketing possibility because it happens more often than the oil cooler
lines failing.

Just another thing to add to the visual inspection checklist. And if the source of the leak isn't
obvious, then I like GoToGuy's idea to refill the engine with oil and fire it up. (Maybe enlist a
helper to Start / Stop the engine, for it shouldn't take long for the leak to reappear. (!)

Let us know what you discover. Failure photos a plus.