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3.1 oil blow by at the firewall mystery leak


bender01

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This 91 olds cutlass has developed an oil leak that sprays oil under the hood in the center near the firewall. it has been looked at a few times by a friend who is baffled. The throttle body has been off a few times, there was a little oil in there. He said pcv valve checked  I think and some Gaskets were changed. Its not the valve cover gasket thats dry once he got there. Heres the kicker. It only does it under a load. It will idle fine and rev up no oil. As soon as its gone a few miles it pushes a few tablespoons up and hits the underside of the hood! Im afraid to take it to a true mechanic as im sure the price will be astronomic. Second owner rust free car with 73k miles.

 What could be putting oil pressure in gear to blow oil like that?

  Thanks

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Are you sure it's oil?  Sounds like the trans could be overfilled and blowing up through the dipstick tube.

That makes sense.

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No its oil. Under the car it comes down closer to the passenger side on the engine. What doesnt burn up. I need a lift to get under it and really see. Its a sharp car but im tired of pouring money in it! I did the AC last fall! $$$ about 200 miles ago!  Its coming from somewhere behind the throttle body. Thanks for the replies and keep them coming.

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It's the o ring on the oil pump drive gear.  Pull off the throttle body, or even better the whole upper intake, and replace that seal.

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I'm confused. 

 

It sounds like it could be PCV related but Its not like the crankcase is under pressure which would usually rule out that spraying oil unless the PCV hose is totally ruined and its leaking some blow by oil out the back and down that way, but then I'd think the car would have a pretty wicked vacuum leak.

 

I'm kinda going with the oil pump drive seal myself. Get a flashlight and look down under the TB and see how much oil there is.

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Are you positive it's not power steering fluid?  I know it sounds silly, but I can't imagine a leak point that would allow that much to spray out and hit the hood...but a pinhole leak in a power steering hose would, and they're on the passenger's side, before they disappear under the cradle.

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It's the o ring on the oil pump drive gear.  Pull off the throttle body, or even better the whole upper intake, and replace that seal.

 

 Right, which is something 3.1s suffer from (or their owners rather). Mine had it, never fixed it. People on this list way back when I had it recommended not only replacing the o ring, but also adding a felpro paper gasket to make sure it should never happen again.

 

 As an aside, I can't understand how this could be the problem when you need to take off the plenum to get to it (IIRC). No, I've never done it, so therefore it's clear I guess why I can't imagine it spraying oil on the bottom of the hood.

 

 And though I never got into these aspects of repair with my old Lumina, did with my Venture. removing the plenum is a friggin joke. Not recommending it but I didn't even torque the bolts down, just went by feeling (w/the lower manifold, you need to torque). I was skeeeeered of popping off the plenum. But it's so not a heart pumping crisis. I ***ALWAYS*** recommend buying a box w/separate compartments, and LABEL and put the bolts solitary compartments, this way you can feel good about putting exact same bolts where they belong ;).

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 People on this list way back when I had it recommended not only replacing the o ring, but also adding a felpro paper gasket to make sure it should never happen again.

 

 As an aside, I can't understand how this could be the problem when you need to take off the plenum to get to it (IIRC). No, I've never done it, so therefore it's clear I guess why I can't imagine it spraying oil on the bottom of the hood.

Agreed.  The oil pump drive is a leaker, not a sprayer.

 

Lumina_Oil_Pump_Drive_01.JPG

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It is power steering fluid!   I put a whole bottle in last fall. Its almost out again.   It hits so much spraying on the way up it looks like oil! Til I compared it to my dipstick! 

  Thanks for the help. Ill post back when its fixed. Thanks again 

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my 1997 3100 is leaking like a mofo too, but mine is Engine oil... see pics.... hope its the oil drive seal  but i doubt it :bash:

this one's gonna be a PIA to feex

118ff4475756810.jpg 9d7ae5475756912.jpg 

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Glad it's fixed.  At the time, I know it might have sounded a little weird to suggest it could be power steering fluid...

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