6.9 Head Gasket
Freshman User
Joined: Apr 2000
Posts: 49
Likes: 0
From: Sedro Woolley, WA
The most common failure on the 6.9 is an external leak of coolant at the rear or front of the head. Look for coolant streaks in these areas. Or you will have coolant in the oil. Look at your oil cap. Does it have a greyish looking gunk on it? How about on the dipstick? Or you can have compression gases leaking into the coolant which is cause your coolant to overflow and bubble. Some of these symptoms won't show up unless the engine is hot. Or you can have oil leaking externally (not as common).
If you do change out the gaskets I highly recommend to go to studs instead of headbolts which will lessen the likelyhood of another headgasket leak because the headbolts are too small (7/16") and there aren't enough of them so they end up stretching.
If you do change out the gaskets I highly recommend to go to studs instead of headbolts which will lessen the likelyhood of another headgasket leak because the headbolts are too small (7/16") and there aren't enough of them so they end up stretching.
Tuned
Joined: Oct 2004
Posts: 250
Likes: 6
From: new york
I don't think its a head gasket, their sympton are usually overheating, loss of antifreeze, deluted oil with antifreeze. It could be a bad injector or possibly burnt valve or other internal problems. First off you need to find out which cylinder has the miss, If it misses right from a cold start, you can start it cold, let it idle and feel the exhaust manifold at each cylinder, you should notice one that is a little less hot. If not you could try lossening the injection lines while the engine is running, its a little messier but may indentify the problem, only loosen one at a time, listen then tighten it back up if the cylinder is dead when the injector line squirts out fuel there will be no noticeable change in idle, but all the other cylinders will make it idle worse. Keep in mind that finding a slight miss is a pain in the a** without a compression gauge and a strong understanding of what causes it. If you do find which cylinder is bad I would remove that injector and swap it with another one, then recheck to see if the miss moves with the injector ie bad injector.
New User
Joined: Jul 2017
Posts: 1
Likes: 0
my 86 6.9 diesel has a hard time starting and when it starts it runs like completely horrible like its only running on 4out of the 8 cylinders and pours out whit smoke but if I give it acceleration it stops kinda and it has no power wether I give it 5% throttle or 100% throttle need help I can't figure out what's wrong with it
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Lead Driver
Joined: Apr 2008
Posts: 6,938
Likes: 13
If its burnt out between 2 cylinders the only symptoms it will have is a miss. Loosen the injector lines 1 at a time while its idling to find the miss fires. If theyre next to each other, odds are its the gasket. Once found, you can pull the injectors and see if it/ they have any compression.
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