V.P. 5.0GI Intake Manifold Oil Leak

badger42

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May 19, 2009
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Several weeks ago I had both heads replaced (both sides cracked) on a recently purchased boat/engine- 1999 5.0GI PWTR with SX drive.

The mechanics put the engine back together but it leaked oil from the back of the intake manifold near the distributor, actually right near the oil pressure sensor. I took it to a partner dealership closer to the house to get it fixed again, but it still has the same leak.

At Idle, it puffs smoke out of a small hole in the RTV sealant between the intake manifold and the block; while running under load it blows out oil. As far as i've seen there is no actual gasket, just a line of sealant in this area.

Any suggestions for getting this right- I'm considering asking for my money back and doing it myself.

- Thanks
 

WELEPRO

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Jun 29, 2010
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Re: V.P. 5.0GI Intake Manifold Oil Leak

I realize this is an old post, but my '97 Merc 350 is doing EXACTLY the same thing. Block/Heads are new(less than 15 hours), only thing transferred from the old freeze cracked engine was the intake manifold, This oil leak is a real mystery.

What did you discover? Can anyone else chime in?
 

Bt Doctur

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Re: V.P. 5.0GI Intake Manifold Oil Leak

OK , here `s the secret to GM manifolds


Clean the block and manifold with acetone, let dry
Place a 1/4 inch thick bead of Black RTV sealant on the front and rear of the block
install manifold and just start all the bolts
LET CURE OVERNIGHT
Torque bolts to spec.
 

John_S

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Jun 21, 2004
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Re: V.P. 5.0GI Intake Manifold Oil Leak

OK , here `s the secret to GM manifolds


Clean the block and manifold with acetone, let dry
Place a 1/4 inch thick bead of Black RTV sealant on the front and rear of the block
install manifold and just start all the bolts
LET CURE OVERNIGHT
Torque bolts to spec.

On vortec heads, like the OP probably has, I'd be a little concerned the cured rtv would prevent sealing of the o-ring type gaskets with so low torque values. I'd like to hear more on this and experiences. I have always torqued before cured, but only have done a handful compared to yourself.
 

Bondo

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Re: V.P. 5.0GI Intake Manifold Oil Leak

On vortec heads, like the OP probably has, I'd be a little concerned the cured rtv would prevent sealing of the o-ring type gaskets with so low torque values. I'd like to hear more on this and experiences. I have always torqued before cured, but only have done a handful compared to yourself.

Ayuh,... Not on the gasket face of the head, Only to replace the rubber pieces between the intake manifold, 'n Block....
Fore 'n Aft....

Btw,... I let it set up, but not cured overnight...
 

John_S

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Re: V.P. 5.0GI Intake Manifold Oil Leak

Ayuh,... Not on the gasket face of the head, Only to replace the rubber pieces between the intake manifold, 'n Block....
Fore 'n Aft....

Btw,... I let it set up, but not cured overnight...

Yep, understand it is not on the gasket face, and ditching the rubber gaskets (don't believe they come with the o-ring style for vortec.) My concern is having a 1/4" bead of cured silicone which is probably higher than the soft o-ring. 133 lb. in. (15 N.m) is not allot of torque. Maybe not an issue, but have heard of sealing problems with vortec intakes.
 

WELEPRO

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Re: V.P. 5.0GI Intake Manifold Oil Leak

Ok...this is good info. My engine is not a Vortec, but I'll take the advice either way.
 

carcraze

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Messages
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Re: V.P. 5.0GI Intake Manifold Oil Leak

Okay somewhat related but since I have not done a 350 marine only a few Fords and now have GM.

When we did 350 in cars way back when we always used the rubber gaskets between the manifold and the block. I am wondering why the recomendation to loose them and is this for both cars and marine as i can not see a reason why marine would be different?
 

John_S

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4,269
Re: V.P. 5.0GI Intake Manifold Oil Leak

Okay somewhat related but since I have not done a 350 marine only a few Fords and now have GM.

When we did 350 in cars way back when we always used the rubber gaskets between the manifold and the block. I am wondering why the recomendation to loose them and is this for both cars and marine as i can not see a reason why marine would be different?

Yea, the rubber gaskets were a pain back then, too. It was easy to end up with oil seepage. If I was to do a SBC for the road, would do it the same as the Merc manual. If you order the GM gaskets for vortecs, the rubber ones do not come with them. So, I'd say they made the change for cars, as well.
 

carcraze

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Messages
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Re: V.P. 5.0GI Intake Manifold Oil Leak

Thanks for the info, makes sense as you are right they were a pain.
 
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