Merc 5.7 leak

[Onexl85]

Anyone ever hear of oil leaking from a 96 mercruiser 5.7 by running up the threads of the intake manifold bolts?

 

[Scott Danforth]

No, that would be a new one.

do you have oil sitting on top of the area between the head and intake? if so, could be coming out the breathers

 

[Onexl85]

Do you mean the valve cover breather? My marina said its running up the threads

 

[grewvin1]

Never heard of that one, check the valve cover gasket.

 

[imp0ster]

Unless one of the intake bolts is running into an oil galley it's impossible. Take a picture. You're probably getting oil on a belt and it's throwing it up there

 

[Bt Doctur]

Water if the bolts did not have sealant on them but never oil. There are no oil galleries present in chevy heads

 

[Fishermark]

Not only is it possible, it is common. You need to use sealer on the manifold bolts. I like Permatex #2 - but ARP makes a good sealer - and other options are available as well. But yes, the bolts need to be sealed.

 

[Fishermark]

Just as a follow up - if you have the older style heads and intake with 12 bolts, then yes - those holes go into the oil gallery and absolutely need to be sealed. On the "newer" style Vortec heads with 8 bolts... on those I am not sure. Those MAY be blind holes. But if your shop is saying the oil is wicking up through the bolts then you need to use a sealer after thoroughly cleaning the bolts and holes.

 

[Onexl85]

Wow I thought they were maybe yanking my chain! They are the older non vortec heads. Been through hell with this engine leaking

 

[Onexl85]

Btw, after only a short ride maybe 4 miles on the river, had a good puddle on top of the engine

 

[Bt Doctur]

That would suggest no crankcase venting to push oil upward. The center bolts do extend into the lifter valley area and the end bolts enter the cooling chamber in the heads

 

[Bondo]

Ayuh,.... Easy enough to fix, just run 'em out one at a time, dope it up, run it in, 'n move on to the next,.....

 

[Onexl85]

Yea, their doing that.......had my heads rebuilt last year by them, been leaking ever since. Gotta give em credit.....they are standing by their work

 

[Onexl85]

That would suggest no crankcase venting to push oil upward. The center bolts do extend into the lifter valley area and the end bolts enter the cooling chamber in the heads

Do you mean the bolts are leaking because there is no crankcase ventilation? What causes that?

 

[Fishermark]

Insufficient ventilation can make it worse, but without sealer of some sort they will leak.

 

[Onexl85]

What would cause poor ventilation? I don't have pcvs just 90 degree fitting with flex tubing to the carb

 

[Onexl85]

Do you guys know what bolts go into oil galleries?

 

[Fishermark]

I would have to look... but if memory serves, it is all except the end bolts.

 

[flipbro]

The 4 middle bolts of intake. I've never seen oil weep out through the threads.

 

[Onexl85]

It seems to be the two that also hold down the drive resivoir and the front two on the port side