4.3 Merc oil leak on top of intake

[Evinrude Boater]

Noticed a puddle of engine oil on top of the intake manifold on the port side of the carb. Looks like it's coming up from the manifold bolt at that location. The bolt seems tight. Is this likely a loose bolt or leaking gasket?

 

[Evinrude Boater]

Re: 4.3 Merc oil leak on top of intake

I couldn't get a torque wrench on the suspect bolt without removing the carb but another bolt beside it was less than 40 lbs-ft. I wiped up the oil and will watch to see where it comes from next time out.

 

[Alpheus]

Re: 4.3 Merc oil leak on top of intake

No oil runs through your intake manifold. Check for a leaking valve cover gasket...

 

[Bondo]

Re: 4.3 Merc oil leak on top of intake

I couldn't get a torque wrench on the suspect bolt without removing the carb but another bolt beside it was less than 40 lbs-ft.

Ayuh,... That's Good,... They're supposed to be 35ft.lbs...

 

[Evinrude Boater]

Re: 4.3 Merc oil leak on top of intake

Ayuh,... That's Good,... They're supposed to be 35ft.lbs...

Did I get the wrong information from Manual 7?

 

[Evinrude Boater]

Re: 4.3 Merc oil leak on top of intake

I wiped up the oil and had a look after running for a while and the puddle is back again right beside the manifold bolt at #3. I swear it's coming up that bolt and running into the cavity in the manifold. There's no oil leak at the valve cover. Even if it did, the oil wouldn't make it into the manifold cavity without wetting everything around it.

 

[paultjohnson]

Re: 4.3 Merc oil leak on top of intake

My oil pressure sending unit extender had a leak in it I have oil in the same spot and it was dripping down the back of the engine. I have not had a chance to try the boat with a repaired oil pressure S U extention But it is in the same vicinity Maybe ???

 

[Evinrude Boater]

Re: 4.3 Merc oil leak on top of intake

Paul, my oil leak is on the port side in the middle of the engine right beside the carb. It puddles on top of the intake manifold.

 

[paultjohnson]

Re: 4.3 Merc oil leak on top of intake

OK I guess the puddle on mine was back a few inches Going on memory here. It was on the port side also and on top of the intake manifold like yours, Just in front of the OP sending unit

 

[Adirondack]

Re: 4.3 Merc oil leak on top of intake

Would your puddle by chance be forming under your crank case breather hose? The one that comes from the valve cover? Possibly getting some oil up in that hose and it's dripping at the flame arrestor connection? Maybe post a picture?

 

[Evinrude Boater]

Re: 4.3 Merc oil leak on top of intake

Would your puddle by chance be forming under your crank case breather hose? The one that comes from the valve cover? Possibly getting some oil up in that hose and it's dripping at the flame arrestor connection? Maybe post a picture?

No the breather hose outlet is more forward and I don't see any dripping or running. The attached photo shows the location of the puddle just forward of the #3 intake tunnel, although I've soaked up the oil already. The only way I can see oil getting to that location is from the intake bolt. Can my oil pressure be that high that it's pushing up through there?

 

[muc]

Re: 4.3 Merc oil leak on top of intake

You might want to remove the bolt and clean it. Paint the bolt with perfect seal and reinstall.
Good Luck Muc

 

[Joshua Nichols]

Re: 4.3 Merc oil leak on top of intake

HMMMM for sure a head scratcher.. Wouldn't happen to be blow by. Would it?

 

[BAproject]

Re: 4.3 Merc oil leak on top of intake

You absolutely have to torque the intake correctly or you will have more problems than a small oil leak....like water dripping into the oil pan, followed by replacing the motor!

 

[John_S]

Re: 4.3 Merc oil leak on top of intake

You might want to remove the bolt and clean it. Paint the bolt with perfect seal and reinstall.
Good Luck Muc

Yes, the intake bolts need sealent or oil can wick up the threads and collect on the intake.

 

[Evinrude Boater]

Re: 4.3 Merc oil leak on top of intake

You might want to remove the bolt and clean it. Paint the bolt with perfect seal and reinstall.
Good Luck Muc

Assuming that's where the oil is leaking, is Perfect Seal going to do anything now that the mating surface has oil on it? Am I better off just cleaning the mating surfaces of the bolt head/intake and apply the sealant there?

 

[paultjohnson]

Re: 4.3 Merc oil leak on top of intake

After thinking about this I went out and inspected mine I have a 86 4.3 I have oil in the exact same spot. I know it defies ALL logic but it seems as to be dripping of the throttle lever Which had oil on it too. But that makes no since singe the vacuum of the carb would pull oil into the engine and the only oil that could feseble be there would be getting sucked in from the breather hoses. So that just doesnt make since. However that intake manifold bolt looks pretty secure. to have that much oil puddling up seams like a longshot to me [no disrespect to other posters! Im just throwing out some thoughts!] Before I started backing out secure manifold bolts- I would feel like that might start new leaks- I would try to determine if the oil is coming UP to the manifold or DOWN to the manifold. Maybe rig something like-dont laugh=- cut a piece of thin cardboard, like from a shoebox? and cover the area where the oil puddles and figure out a way to secure it. wedge it between valve cover and carb? be creative. Go run your boat. If the puddle appears and there is no oil on TOP of the cardboard. It came UP, thru manifold bolt? dunno bout that, valve cover ? If there is oil on TOP of the cardboard but no puddle , its coming from above- carb ? cant see it- oil fill cover? breathers? I know this is some half-***** backwoods troubleshooting ideas. BUT they are ideas.. Good luck I will be following this post so when you figure it out I will know how to fix mine!!!

 

[Adirondack]

Re: 4.3 Merc oil leak on top of intake

I'm with Paul on the throttle plate rod dripping a bit. I see corrosion in that particular manifold pocket and from this view the rest look pretty clean. Oil won't cause that, but dripping gasoline evaporating, and leaving an oily residue may. It may not actually be dripping when running, but after running when the engine is hot. Gas sits in the bowl of the carb and heats up. If the float level is high in the bowl it can expand an cause a minor "flooding" condition that isn't even noticable. A bit of raw gas drips on the throttle plates, and wicks out the rod.

Otherwise if your sure it's oil I would just pull that bolt out and seal the threads up with rtv, or some other sealer and give that a try.

 

[John_S]

Re: 4.3 Merc oil leak on top of intake

I see corrosion in that particular manifold pocket and from this view the rest look pretty clean.

I believe the pocket you are talking about is right next to the exhaust crossover passage. This gets very hot, and peels the paint, which leads to rust.



You are not going to hurt a thing on old style (non-vortec) intake by removing one bolt, cleaning threads, applying sealant, and retorqueing.

Yes, it can be blow bye. Under wot there is little to no intake vacuum. So oil can drip or collect from it. If from this, and hoses, etc are in good condition, sign of engine getting tired. It will gradually get worse.

 

[Evinrude Boater]

Re: 4.3 Merc oil leak on top of intake

I had the carb off for another reason so I took the opportunity to retorque the manifold. They all took about a quarter turn to come up to 35 ft. lb. We'll see what happens.