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Spark plug blowout

8K views 7 replies 3 participants last post by  tundrabubba 
#1 ·
2006 Crew w/ 4.7l...200k miles...Original owner...Never changed plugs(I know, right?) so they are factory installed...Today started hearing what sounded like a "knock" from the left bank...Thinking lifter maybe but it turned out to be the second from rear spark plug (#?) had come out of the block and was banging up into the coil pack...The plug threads were a little rounded off and wouldn't go back into the block...Tried new plug and it won't start in either...Anybody ideas?...BTW no miss firing and the plug had a normal golden brown color :)
 
#4 ·
This is about the only answer to this question, but it is risky due to (1) the possibility of chips falling into the cylinder and later scoring the bore, and (2) getting the tap started improperly and cross threading the hole. I'm glad I don't have to personally deal with this problem.

You have two choices: (1) You can pull the head to insure no chips fall into the bore, or (2) cover the tap with wheel bearing grease to trap the chips and prevent them from falling into bore (not guaranteed, still a little risk). If you choose (2) you'll have to be extremely careful to get the tap started straight into the hole. :frown2:

It's an old truck with 200K miles...maybe the easy way, (1), is justified. How much do you love your old truck. You get to choose.
 
#3 ·
Thanks...That's my thinking too...Was able to get a picture taken down in there and can see threads so hoping chasing will work...Hard to believe it took 12 yrs and 200k miles for it to come out...Gonna change all the plugs now and that one pretty beat up coil pack :)
 
#5 · (Edited)
Hole wallowed too much for re-threader...Went with tap kit from NAPA that had 4 inserts 3/8 7/16 1/2 3/4...Used the 1/2...Used grease and tap oil on tap...Caught most of shavings...Vacuumed out cylinder repeatedly as well as blowing out repeatedly...Lastly started engine and let it blow a bit...Coated insert with hi temp Permatex, screwed it in on the plug till it snugged against the insert flange...Let it cure 24hrs...Then gave the plug enough torque to make sure the gasket was seated...Droved it 60 miles home...Today gonna re-torque and check for blow-by and hope for best :)...Also gonna replace the other 7 plugs and hope no issues with them...Take-aways so far : 1) The threads were obviously stripped at factory and made it 12yrs/200k 2) Although the kit I used had a flange on the insert to prevent going in too far, with more research I would've gone with the kit that had the tap, screw in tool and punch to mechanically lock the insert. Bought that kit after tapping with first kit tap hoping the insert would fit but it had different dia. and thread pitch :( 3) If this works I don't plan to remove that plug...ever :)
 
#7 ·
Update...In replacing other 7 plugs found the plug in the same position on the right bank was hand loose...There was evidence of blow-by but threads were ok and the new plug tightened normally...All old plugs looked normal color wise and there was no rough running...Again these plugs were factory installed in 2006 ish and 200k old...
 
#8 ·
One final thought for anybody interested...Since I've found another plug loose I think the issue with the first one that blew out was that it had worked itself out over time...This wallowed the head threads rather than them being stripped out by over tightening...I've never experienced or heard of plugs loosening up (aluminum heads vs not?) but now I know...I'll check them periodically and of course change them out much sooner :)
 
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