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Discussion Starter · #1 ·
So today I experienced white smoke bellowing out of the exhaust. Tap the gas, it dissapears idling it just sends it. My immediate response was blown head gasket. I have checked the dip stick, no milky oil or high level. Opened valve covers, i have black oil. Except for some light miklyness on the top, insode of cover. I belive this is just moisture. When i opened the hood. My overflow coolant tank was full and was spewing some outside. I relive psi on the radiator cap and the overflow tank bubbles. Radiator has some coolant left in it but not much. No coolant leaking external of the radiator, pump or outside the engine.. did a psi test on the radiator cap, good. The system didn't hold. Got it to 11psi and I can see it very slowly dropping psi. Spark plugs are next to inspect before I will start to take parts off. Oil smells and looks like oil, coolant smells and looks like coolant. Its a 350 sitting in a 86 c10. Any other advise or tips are greatly appreciated before I go tearing this motoar apart. Thanks in advance.
 

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" have checked the dip stick, no milky oil or high level " It all depends on where the head / gasket goes whether it mixes with the oil or not . Coolant reservoir is pressurising , indicative of head / gasket . It can be blowing out the exhaust rather than mixing with oil and you need to carry out a block test to confirm or not .
 

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" have checked the dip stick, no milky oil or high level " It all depends on where the head / gasket goes whether it mixes with the oil or not . Coolant reservoir is pressurising , indicative of head / gasket . It can be blowing out the exhaust rather than mixing with oil and you need to carry out a block test to confirm or not .
Been there, done that. Had a bad head gasket which did not effect the oil but sure steamed up the neighborhood. If you have dual exhaust it will be easy to determine which head gasket is bad.
 

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Discussion Starter · #4 ·
Thanks for the replies. Im gonna do a leak test on it this weekend. Now its Just why did my head gasket blow. My experience is with marine diesel engines. I did smoke out the neighborhood but have single exhaust. Well duel but it "Y" from the muffler.
 

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Did you pull the plugs? You can tell which head it is by doing so. Look for the plug(s) that are super clean or even a reddish color.

Head gaskets just sometimes fail. Its probably nothing to be concerned about. Just be sure to check the head and the piston(s) for any damage or cracks.
 

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Discussion Starter · #6 ·
Did you pull the plugs? You can tell which head it is by doing so. Look for the plug(s) that are super clean or even a reddish color.

Head gaskets just sometimes fail. Its probably nothing to be concerned about. Just be sure to check the head and the piston(s) for any damage or cracks.
O haven't pulled them yet. I know that if coolant is in the cylinder the plugs would be shinny or as you stated clean. I hope there is nothing causing it to go. The engine is only 6 years old. Swapped it from the 305. Should i still send the heads off to a machinist to be sure or only if there is no evidence of a leak by. If the gasket just failed, which I hope if anything is the problem, than i shouldn't have to send the headers off. If im not mistaken.
 

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You will be able to see the fault on the gasket. Be sure to inspect the underside of the head for any visible cracks. If you haven't overheated the engine I'm betting the head is alright.

If you want to take the head to a machine shop they can magnaflux it (metal powder and electromagnet) and tell pretty quick if there is a problem. Have a good look at the gasket first. Use a quality gasket for replacement such as Fel-Pro or ect.
 

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Discussion Starter · #8 ·
You will be able to see the fault on the gasket. Be sure to inspect the underside of the head for any visible cracks. If you haven't overheated the engine I'm betting the head is alright.

If you want to take the head to a machine shop they can magnaflux it (metal powder and electromagnet) and tell pretty quick if there is a problem. Have a good look at the gasket first. Use a quality gasket for replacement such as Fel-Pro or ect.
Awesome! thanks for the information.
 

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White smoke? THM 350 or 400? Could be vacuum modulator diaphram ruptured. Sucks tranny fluid into intake and makes tons of white smoke. Beem there, done that. Pull the vacuum hose off the modulator and see if it;s full of the red fluid.
 

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Done a lot of different makes in the shop where the vacuum modulator diaphragm ruptured and and as you say causes the smoke . But in this case he has the cooling system overheating and pressurising also so more likely to be head / gasket , but wont do any harm checking
 

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And another tidbit. If the intake gasket sucks coolant you might have mistaken it for a blown head gasket.
Sometimes the only way to determine the cause is teardown but you must have a direction as to what you're looking for, most times the intake gasket will seperate as the manifold is lifted destroying the evidence. So one must be certain it's not a head gasket first. Compression test followed by cyl. leak down would be poof positive in my book. If the head shows to have a problem don't waste money on anything put pressure checking as that's a better way to find a crack in the head. Which is most likely under the exhaust seat which won't show on magnafluxing unless the seat is removed. Good luck!
 

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Discussion Starter · #14 ·
Soo update. I haven't been able to work on this as much as i want. However, i have got everything disconnected, bagged, tagged and finally removed the driver side header. Now its removing the passenger side, renewing gaskets and reinstalling everything and done.. hopefully.

It wasnt the vacuum modular. Checked that before pulling a single bolt.

I pulled the spark plugs and tried cranking the engine over and coolant flew out of cyl 2 and 4. Pulled header off to find 1 with excess carbon build up, 3 and 5 clean and 7 partially filled with coolant. Not sure if it happened when i unbolted the bottom mounting bolts. The oily jw mixture wasnt emulsified so maybe it was from me pulling the bolt out. looked at gasket and can see some issues but driver side was never in question. Will update when passenger side is pulled.
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Notice the gasket between the 3 & 5 cylinder? The pistons and valves for those cylinders do look mighty clean. I think you've found it. 7 & 8 always get the coolant when pulling the head due to the engines tilt at the rear.

Out of curiosity, is there much ring wear at the top of the cylinders?
 

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Discussion Starter · #17 ·
Notice the gasket between the 3 & 5 cylinder? The pistons and valves for those cylinders do look mighty clean. I think you've found it. 7 & 8 always get the coolant when pulling the head due to the engines tilt at the rear.

Out of curiosity, is there much ring wear at the top of the cylinders?
As soon as i pulled the head off i noticed that black inbetween 3 and 5. No visable cracks in head but i think the head is fine. The gasket failed. Yeah 3 and 5 were noticably cleaner looking than 1 and 7. And figured the jw in 7bwas from me pulling as youbsaid it has a lean to the rear. I also haven't seen a worrysome amount of ring wear. Looking forward to thursday when the passenger side is coming off..
 
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