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Unread 06-06-2013, 12:37 PM   #1
jetboat
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1987 YJ Wrangler 
 
Join Date: Mar 2007
Location: romeoville, Illinois
Posts: 31
oil pressure?

Whats the proper warm idle pressure for a 4.2?

I am getting horrid lifter knock when warm and my gauge is broke... I hooked up a manual gauge and am showing 13-14psi at idle when warm and it jumps up near 50 when you rev the motor. Start up cold pressure is 54.

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Unread 06-06-2013, 12:42 PM   #2
Old4X
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1990 CJ7 
 
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Location: Ga
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Sounds good to go. IIRC, 10 psi idle plus another 10psi for every 1,000 rpms above idle.

Biggest problem is people running water thin oil. Should be running 15w-40 rotella.
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Unread 06-06-2013, 12:47 PM   #3
jetboat
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1987 YJ Wrangler 
 
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Location: romeoville, Illinois
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Ive been running 10-30 synthetic... Ill swap it for some diesel oil.
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Unread 06-06-2013, 12:54 PM   #4
Old4X
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If you have a knock instead of a tick, it is either broken or bent valve train parts, or (more likely) worn out timing chain and gears.
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Unread 06-06-2013, 01:34 PM   #5
jetboat
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1987 YJ Wrangler 
 
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Location: romeoville, Illinois
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mechanic neighbor looked at it and said it sounded like a collapsed lifter to him... it has a tick all the time but, as the temp comes up it develops a defiantly loaded tick that I consider a knock.
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Unread 06-06-2013, 02:05 PM   #6
Old4X
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1990 CJ7 
 
Join Date: Nov 2008
Location: Ga
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You can check easily by pulling the valve cover and run the engine. Feel each rocker, a loose one is obvious.
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