Coolant leaking from valve cover

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blacks78cutty

Not-quite-so-new-guy
Oct 11, 2008
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i just had my 78 350 olds rebuilt and i am starting it for the first time. for some reason i have coolant leaking from one little spot on my valve cover. it is right above the #6 sparkplug. it drips down onto my exhaust manifold and causes alot of smoke. it only does this when the car is running and for about 2 minute after i turn it off. can someone please help me. i have put to much money into this car and cant afford to lose it right now. i could not find any cracks. car runs fine.
 
Are you sure it's not oil? If it is coolant, you have a MAJOR problem somewhere since coolant should not be anywhere near it! Try tightening the valve cover nuts snugly, but not over tight. Choke up on the wrench so that your hand is on top of the ratchet head. DO NOT USE THE END OF THE HANDLE!!! If you do, you will over torque it and warp the valve cover flange.
 
Is there a heater hose that runs right above that area? If so, make sure it is not leaking.
 
yes im sure. when i turn the car on i wiped that spot dry with a towel to find where it was coming from. and i could see it slowly starting to drip and puddle up around that spark plug again.
 
i thought that to. so i replaced the heater hoses and the heater control valve. no luck.
 
Very possible that whoever rebuilt the engine re-tapped the threads for the valve covers and went too far hitting one of the coolant passages in the head. You'll likely need to pull the valve cover and run the engine for a few minutes to see just where the coolant is coming from.

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if i take the valve cover off what do i do once on find it
 
Good question. You are probably going to find what I mentioned or a small crack in the head somewhere. If it's down in the valve cover bolt hole, you can fill the hole with some RTV and put the bolt back in and it will likely stop the leak or have the threads repaired with a heli-coil using a sealant on the heli-coil while inserting it. If the head has a surface crack, you are likely going to have to replace the head. Put a rag on the lower part of the head above the exhaust manifold to catch the oil while running the engine with the valve cover off or you'll have a smokey mess.

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Is any coolant getting into the oil?
 
The coolant leak flows downward, so it's probably up on the lip for the valve cover somewhere. Some could leak to the inside of the valve cover and get in the oil. Olds engines usually just use RTV for the valve cover gasket, so you can take the suspect valve cover bolt nearest to the leak out and run the engine and see if coolant gushes out the hole.

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