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 Post subject: ??engine?? troubles
PostPosted: Mon May 15, 2017 4:07 pm 
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hey guys, first post so lets start with hey! new jeep owner, got my first wk about 2 months ago, still not sure if that was the right decision..lol. been having an issue pretty much from day one, searched everywhere, watched way to many you tube videos and cant seem to get anywhere with it. apparently no one works on wk's...lol. ive got a 07 wk with the 3.7, 150,000km on the clock. ive been hearing what i think is engine knock for the last month or so. its a very faint knock that appears at 7-800 rpm and goes away at 11-1200 rpm. its present in drive, reverse and park. its present when the engine is cold and up to operating temp, no change. it doesn't sound like the famous 3.7 loose rocker arm, i have had the valve covers off to confirm. Ive had the drive belt off and the noise is still there. checked all the u joints and cv's, all tight with no excessive play, there is no exhaust manifold leaks that i can see. the oil pressure light did flicker a few times when coasting to a stop, that has happened on 2 occasions. the intermittent oil light combined with the knock made me think main's or connecting rods, however i would think that the noise would only get worse as rpm's increase. i am going to pull the oil pan anyway to check for sure. just wondering if anyone has had anything similar or could point me in the right direction.

thanks in advance!!


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 Post subject: Re: ??engine?? troubles
PostPosted: Tue Jul 04, 2017 3:35 pm 
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How did this end up playing out?

I had a rod bearing problem with my first engine and it died at 86K. But yes, the noise got worse with increasing RPM's especially when not under load.

I would say this problem is rare though. I haven't heard of many other 3.7's that died at low mileage because of this.

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Trailer build thread: viewtopic.php?f=72&t=77997


Last edited by lfhoward on Wed Jul 05, 2017 9:10 pm, edited 1 time in total.

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 Post subject: Re: ??engine?? troubles
PostPosted: Tue Jul 04, 2017 7:17 pm 
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Hook up a direct pressure oil pressure gauge. Rev it up a bit, then let it return to idle.
IF the higher oil pressure from being revved doesn't fall as fast as the RPM, the pressure bleed-off could be Hydraulic adjusters or something else.
Since oil volume from the pump is fixed per revolution, It sounds as if something is bleeding off volume faster than the pump can deal with at low RPM.
I have had engines in the past which had hydraulic valve adjusters sound very much like a rod knock at low rpm because they stuck at a collapsed state due to not enough oil pressure at low rpm. Revving the engine up sometimes makes them pump up again.
If the oil pressure drops in direct concert with the falling engine rpm, it's more likely to be a bearing or a stuck pressure relief valve... something leaking a larger volume of oil.

Send an oil sample to Blackstone Labs. They should be able to identify what materials in the oil are excessive.

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 Post subject: Re: ??engine?? troubles
PostPosted: Wed Jul 05, 2017 9:15 pm 
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X2 on recommending Blackstone Labs. They helped identify a hairline-cracked cylinder head for me years ago on my XJ, saving that engine from a premature death. In that case, coolant was getting into the oil and causing the beginnings of bearing wear.

_________________
2008 Liberty Sport 4x4 Automatic
Image
Jeepin By Al 4" Lift Kit
Goodyear Wrangler Duratracs 245/75/R16
Full MOPAR skid plates
Rock Lizard Skink Super Sliders
AtTheHelm Front Recovery System

Trailer build thread: viewtopic.php?f=72&t=77997


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