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Unread 10-25-2012, 08:25 AM   #1
Fast_SUV
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1997 TJ Wrangler 
 
Join Date: Jul 2007
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2001 WJ limited, another 4.7 Knocking

Hey guys,
I posted this up in the WJ forum but figured it may need to be in here....

I up a 4.7L WJ this weekend from a guy off CL.
We worked out a nice trade so I wont be in it for to much $$; so putting a little $$ in it will be O.K. for me.

He said about a year ago he heard a knock start and wasn't sure what it was, he took it off the road and didn't drive it ofter hearing that.

Any suggestions on things to look at once i get it home to narrow down if it's a rod bearing, timing chain, etc?? I have read a ton and watched a bunch of videos but their knocking seems pretty consistent...

Video of the sound:
http://youtu.be/OiV3Qajs2L0

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Unread 10-25-2012, 11:25 PM   #2
reztech
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rod knock

thats definately sounds like a rod knock. drain the oil if it looks metallic its time for a engine swap. the last used swap i did i paid 1100.00 usd for used engine with 120,000. mitchell labor guide calls for about 10 hrs labor. back yard mechanic is gonna spend 2-3 days.
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Unread 10-26-2012, 07:19 AM   #3
Fast_SUV
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Quote:
Originally Posted by reztech View Post
thats definately sounds like a rod knock. drain the oil if it looks metallic its time for a engine swap. the last used swap i did i paid 1100.00 usd for used engine with 120,000. mitchell labor guide calls for about 10 hrs labor. back yard mechanic is gonna spend 2-3 days.
If there is no metal, or very little would it be worth trying to swap out just the rod bearings to see if it fixeds the issue? At 6-7 buck each plus the new bolts the swap of new bearings doesnt seem to bad (just drop the pan....)
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Unread 10-26-2012, 11:35 AM   #4
reztech
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rod knock

a rod knock that loud would have definately damaged the crank journal. i never recommend tryin to replace bearings only. even with a under sized bearing on that journal you would have excessive bearing clearance.i have known of people who replaced bearings do to a rod knock that severe and when completed they had a slight knock. the rod bearing oil clearance standard spec is .0002-.0019 thats the clearance between the bearing and crank journal thats a really tight clearance. a crank kit would be alot of labor and would need to be done by experienced tech. thats why i recommend used engine swap if your on a budget. if your determined to go the route you said with dropping the pan then a least try to get a under sized bearing on the damaged journal thats knocking.
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Unread 10-26-2012, 01:23 PM   #5
Fast_SUV
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Quote:
Originally Posted by reztech View Post
a rod knock that loud would have definately damaged the crank journal. i never recommend tryin to replace bearings only. even with a under sized bearing on that journal you would have excessive bearing clearance.i have known of people who replaced bearings do to a rod knock that severe and when completed they had a slight knock. the rod bearing oil clearance standard spec is .0002-.0019 thats the clearance between the bearing and crank journal thats a really tight clearance. a crank kit would be alot of labor and would need to be done by experienced tech. thats why i recommend used engine swap if your on a budget. if your determined to go the route you said with dropping the pan then a least try to get a under sized bearing on the damaged journal thats knocking.

When you say "a rod knock that loud would have definately damaged the crank journal" are you meaning rod journal? so where the connecting rod connects....

Pic for reference...
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Unread 10-26-2012, 10:05 PM   #6
reztech
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yes i meant the rod journal. it usually wears down because its metal to metal contact. thats why its important to have the proper connecting rod bearing to rod journal clearance. engine oil pressure create a constant thin film of oil to keep the rod bearing from touching crank journal metal. u can usually determine which cylinder has the knocking rod by disconnecting the injector or coil on each cylinder one at a time while its running. that will take the load off that cylinder when you get to the cylinder with the bad rod the knock will go away or the sound will be less intense.
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