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motor knocking

xXxJay

NAXJA Forum User
Location
british columbia
Hey guys, Ive noticed when i first start my jeep in the morning it knocks for a second ot two. The knock goes away completly even at high rpms on highway. But as soon as i spin the tires (in mud or wet pavement) the revs come up past normal driving rpm, and knock is apparent. motor is out of a 1996 grand. 4.0 with 133,000 kms on it. As far as i could tell when i swapped this motor in 4 months ago it was mint. Great runner, only place leaking oil is the oil filter housing seal.

thanks guys
 
I'm not so savvy on 4.0L internals, but if they are anything like the AMC 4.2 I6s then in all likelyhood you have either worn rockers, or sticking lifters. Some folks think some miracle engine oil additive will solve this, but it's ofetn useless or only works for a few minutes/hours/days. In my experience replacing the lifters and rockers usually got rid of that diesel-ish sounding knocking coming from the head in those old 4.2s. I imagine that the 4.0L isn't terribly different..
 
1. Knock on start up--possible poor grade filter with nitrile rubber anti-drain back valve and you are starting the engine dry. Poor grade filter combined with the 4.0 vertical or horizontal filter = bad news.

2. Leak at OFA--losing oil pressure, fix it.

3. Cold up there? As asked, what oil are you using?
 
thanks guys sorry i took so long. It is a hastings oil filter with great canadian oil change 10w30. I live on vancouver island pretty cold in winter, but not lately. thanks guys.
 
Might want to try a 5w30 or 5w20

your cold temps turn 10w30 into honey.


...piston slap?

Definitely agree with 96XJ_40 on this--different oil, you could add an oil pan heater, and fix the OFA leak--you are losing pressure between the pump and the engine.
 
Changed oil today, good penzoil 10w30 sludge remover shit, with a quart of lucas additive. I put in the most expensive fram filter lordco had. Well see tomorow morning eh.
 
good penzoil and fram dont belong in the same sentence
 
Knock knock.

Who is there?

Fram.

Fram who?

Fram Filter!

Just kidding. Really.

http://people.msoe.edu/~yoderw/oilfilterstudy/oilfilterstudy.html
FRAM:
This filter cartridge has a small outside diameter with a rather low filter element surface area (193 sqin), and features cardboard end caps that are glued in place. The rubber anti-drainback valve seals the rough metal backplate to the cardboard end cap and easily leaks, causing dirty oil to drain back into the pan. If you have a noisy valve train at startup, this filter is likely the cause. The bypass valves are plastic and are sometimes not molded correctly, which allows them to leak. The backplate has smaller and fewer oil inlet holes, which may restrict flow.
Joe, your awesome!
 
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