Where's the oil coming from?

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Sortasuave

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I'm driving a 1990 GMC Sierra with a 5.7L motor.

I've got oil pooling up on the top of the motor on either side of the carburetor.

Where is this oil coming from?

All of my efforts to solve the problem have been on the driver's side of the motor. To date, I've tried resolving the problem by:
  1. Changing the valve cover gasket
  2. Removing the tube you see in the attached file, checking it for cracks/holes (none found) and reinstalling it with new thread tape.

From some other forums, I've seen people describe similar problems. (Sadly none of them had pictures to confirm the same issue.) The few responses I found suggested pulling the bolts on either side of the leak, coating them in black Permatex and reinstalling them. Is that the correct solution?

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smdk2500

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I had the same issue with my 95 except I had oil and coolant pooling up there. Mine started with oil then coolant started as well. What I did was replace the intake gaskets and didn't have any other issues with the year or so driving it after replacing them.
 

SAATR

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Your permatex solution should work. The oil wicks up the bolt threads from the valley and pools where you have it there.
 

Schurkey

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While you're at it, make sure the PCV system, including the suction side and the vent side, are working properly. Excess blowby can pressurize the crankcase, making the oil squeeze out of every possible opening.

"I" would use Loctite/Permatex "592" pipe sealant with Teflon (PST) on those bolt threads. But most any sealant can work although I'd NOT use RTV Silicone.
 
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8thNote

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I'm driving a 1990 GMC Sierra with a 5.7L motor.

I've got oil pooling up on the top of the motor on either side of the carburetor.

Where is this oil coming from?

All of my efforts to solve the problem have been on the driver's side of the motor. To date, I've tried resolving the problem by:
  1. Changing the valve cover gasket
  2. Removing the tube you see in the attached file, checking it for cracks/holes (none found) and reinstalling it with new thread tape.

From some other forums, I've seen people describe similar problems. (Sadly none of them had pictures to confirm the same issue.) The few responses I found suggested pulling the bolts on either side of the leak, coating them in black Permatex and reinstalling them. Is that the correct solution?

You must be registered for see images attach

I have a 94 5.7L TBI, and mine is doing the exact same thing (plus coolant along with the oil). The answer is to replace the intake gasket. That is a very common problem with these engines. I've been putting off doing mine, but it's getting worse so I will have to break down and do it soon.
 

HotWheelsBurban

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I've been told that the orange coolant exacerbates the intake manifold gaskets issue with these motors, due to various leaks over the last 3 years, I've circulated fresh coolant into the system regularly. Think mine may be starting to do it anyway
 

Schurkey

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There's a whole lot of stuff that "orange coolant" gets blamed for.

The first few years of "Deathcool" production and use did have problems. Those problems seem to be GONE now.

Intake gaskets never did last forever. Wouldn't be unusual to have a gasket failure after ~25 years.

Keep in mind that the gaskets are only in contact with oil at the lower edge. Oil would have to wick the entire width of the gasket to provide a visible leak on the manifold. OTOH, oil wicking up the bolt threads is far more direct and more likely, especially if there's some crankcase pressure.
 

someotherguy

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Also, most of the talk surrounding intake gaskets and GMT400's involve the really crummy plastic gaskets used in the Vortec small blocks - they're the ones notorious for failure. The TBI engines used a more conventional gasket material and although eventually they all will fail, they don't seem to fail as soon, or as regularly, as the Vortec pieces.

Oil (not coolant, though) pooling on the middle intake bolts is somewhat common as the holes go right through the heads into the lifter valley. Your sealant application may well work just fine. As Schurkey mentioned it doesn't mean you have intake gasket failure. Coolant leaking, then yes...

Richard
 

Schurkey

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^^^ all true.

The gaskets used with the OEM TBI intake, and the aftermarket DIRECT REPLACEMENTS for the TBI intake are "special" in that the rear coolant passage is blocked-off. Gaskets used with non-TBI intakes have the full-open rear passage.

This is because the TBI intakes are water-heated, using the wrong gasket screws-up the coolant flow path.

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Redneckgeriatric

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^^^ all true.

The gaskets used with the OEM TBI intake, and the aftermarket DIRECT REPLACEMENTS for the TBI intake are "special" in that the rear coolant passage is blocked-off. Gaskets used with non-TBI intakes have the full-open rear passage.

This is because the TBI intakes are water-heated, using the wrong gasket screws-up the coolant flow path.

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reckon what would happen if we did use the old style gaskets? slower warmup? poor mpg? curious!
 
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