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Old 04-07-2013, 11:13 PM   #1
1988jeeper's Avatar
Join Date: Nov 2012
Posts: 2
4.0 motor knock

Ok this is my first time posting. So I got a yj that I purchased about 2 months ago the oil was really black but I ran it like that for about two weeks then I took it to a quik lube because it was still cold out I'm guessing they used cheap oil and 10w30 well after I had that done after it fully warmed up it would start to tick or knock sounded like top end and the oil would be just like water very liquidly so I did an oil change myself and used 5w40 I believe amd that worked fine for about 3 weeks now it starts fine but when it fully heats up it starts to knock pretty loud can someone help me out like what oil should I use or other products sorry for writing a book for you guys . Thanks

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Old 04-08-2013, 12:21 AM   #2
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Join Date: Oct 2012
Location: Corpus Christi
Posts: 483
add some lucas upper cylinder lube

4.0, 4.10 gears,8.8 with lsd, spartan up front, 4 inch rc, 5/8 boom shackles, 1 inch body lift, 33x12.50 toyo mts
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Old 04-08-2013, 10:34 AM   #3
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Instead of running a 5 or 10-40 then adding treatments, do the opposite. Run a 5-20 and don't add thickeners (oil treatments)

The thinner the oil, the faster it will get to the top end.

The loudest my 4.0 ever rattled was after adding lucas... Thinner oil will do wonders, I learned this by having to wait a month after an oil change for it to quiet down. Then, I tried 5-20 and the thinner oil kept it quieter right out of the gate for sure.

A lot of people say to add oil treatments for loud engines not realizing that a lot of time the problem is that the oil is already to thick. By adding treatments your thickening it even worse. 3 years ago, I'd have said to add lucas. Then, I learned that it made my engine a lot louder whenever I would try it.
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1994 Wrangler YJ I6 4.0 H/O Auto 3 spd. 4" RC (33x12.5) (15x8) 3:54 Gears
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Old 04-08-2013, 03:42 PM   #4
Join Date: Jan 2010
Location: Las Cruces, NM
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So is the knock or tapping coming from the valve train....is so could be a dirty lifter..
(Sold)1994 Jeep Wrangler 2.5L, Bestop top
/w steel half door and slider windows
5 speed, 2.5" lift, 31" tires,rack lights
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Old 04-08-2013, 09:21 PM   #5
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Thanks guys ill try thinner oil and see how that goes
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