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Unread 02-05-2011, 06:12 PM   #1
SuperRliBerty
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2008 Jeep Liberty Engine Failure

Found this in an austrailian Jeep forum. I showed it to my mechanic friend and he said either oil starvation, over-revving or camshaft mod failure can cause that:

2008 Jeep Liberty w/63,000 miles. Broke cylinder #4 intake valve spring, which caused the rocker arm to become jammed between the lifter and the cam. Result..... Note this is the 3rd late model Chrysler product this year breaking valve train components and ruining heads. The other 2 were Hemi's.

0617001602.jpg  
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Unread 02-05-2011, 06:28 PM   #2
tjkj2002
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Well you can't over-rev the engine,the PCM will not allow it.76,000 miles on mine and it bounces of the rev limiter at least 10 times a day so that is a non-issue.
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Unread 02-05-2011, 06:37 PM   #3
SuperRliBerty
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Originally Posted by tjkj2002 View Post
Well you can't over-rev the engine,the PCM will not allow it.76,000 miles on mine and it bounces of the rev limiter at least 10 times a day so that is a non-issue.
do you do redline shift ten times a day? Do it for another 76,000 miles.

Have you done a compression test on that engine?
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Unread 02-05-2011, 07:02 PM   #4
richd
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I know there are issues with the HEMIs with valve spring breakage,and bad valve guides,so it looks like Chrysler is have some engineering problems.
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Unread 02-05-2011, 07:06 PM   #5
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Quote:
Originally Posted by tjkj2002 View Post
Well you can't over-rev the engine,the PCM will not allow it.76,000 miles on mine and it bounces of the rev limiter at least 10 times a day so that is a non-issue.
How many rpms is the 3.7L rev limiter set at?
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Unread 02-05-2011, 07:56 PM   #6
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Originally Posted by DaveJKJ View Post
How many rpms is the 3.7L rev limiter set at?
6000 rpm
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Unread 02-05-2011, 07:58 PM   #7
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Originally Posted by richd View Post
I no there are issues with the HEMIs with valve spring breakage,and bad valve guides,so it looks like Chrysler is have some engineering problems.
probably in the cast process of the cylinder head.
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Hood Prop mod. Battery Quick Release mod.
Resonator removed (sounds like a V8 on start up)
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Unread 02-05-2011, 09:11 PM   #8
tjkj2002
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Quote:
Originally Posted by SuperRliBerty View Post
do you do redline shift ten times a day? Do it for another 76,000 miles.

Have you done a compression test on that engine?
The rev limiter is there for a reason,it cuts of fuel to prevent damage.The redline(rev limiter) is alot lower then the actual rpm's needed to do damage in which case is called "floating the valves",basically when the valve spring can not open/close the valve quick enough.The 3.7 was operated at "redline" for several hundred hours with no damage on a dyno,along with every other engine produced today.If hitting the redline would cause damage they would set the redline(rev limiter) much lower then what it is already set at.A little common sense goes along way.


Oh and yes I have done a compression test and well above min specs,just remember the 3.7 does not make peak HP till 400 rpm shy of redline.
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Unread 02-06-2011, 03:33 PM   #9
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Originally Posted by tjkj2002 View Post
If hitting the redline would cause damage they would set the redline(rev limiter) much lower then what it is already set at.A little common sense goes along way.
Absolutely! common sense goes a long way. But hitting the rev limiter 10 times a day will not. If you speak with the designer and builder of the 3.7L I am positively sure they will agree with Hitting the rev limiter 10 times a day for 76,000 miles, but hey, to each his own.

I hit the speed limiter once before in my libby on I-75, 110 mph@ 5500rpm before the computer starts cutting fuel and retarding the timing.
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Resonator removed (sounds like a V8 on start up)
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Unread 02-06-2011, 05:54 PM   #10
tjkj2002
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Originally Posted by SuperRliBerty View Post
Absolutely! common sense goes a long way. But hitting the rev limiter 10 times a day will not. If you speak with the designer and builder of the 3.7L I am positively sure they will agree with Hitting the rev limiter 10 times a day for 76,000 miles, but hey, to each his own.

I hit the speed limiter once before in my libby on I-75, 110 mph@ 5500rpm before the computer starts cutting fuel and retarding the timing.
Yeah like to see how many times your 3.7 would hit the rev limiter when trying to move 2000lbs more weight in Colorado.Hitting the rev limiter will not damage the engine as long as you have oil pressure,if it does you have/had a underlying problem that was the reason for the failure and not hitting the rev limiter.

My '84 Blazer I used for mud drag racing was bouncing off the 7500rpm limiter(MSD 6AL box limited) most of it's life with a 355,never hurt a thing.Would also go up to 7000rpm in my Cutlas with a 350 Rocket(big block),about 500rpm short of "floating the valves"(no rev limiter) and never had a issue either.Pulled alot of long distance/high speed trips in that car with it over 6000 rpm's as it only had a 3 speed trans,and talking about 75+ miles runs here on back roads.
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Unread 02-06-2011, 09:34 PM   #11
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i race my civic in auto X and onon the 1/4 mile. rpms go all the way to 9500 and it has 5300 miles and still going strong. reaching the rev limiter is indeed not that bad. go over it and you see the valves flying through the hood. been there, done that
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Unread 02-07-2011, 06:44 AM   #12
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Originally Posted by tjkj2002 View Post
Yeah like to see how many times your 3.7 would hit the rev limiter when trying to move 2000lbs more weight in Colorado
Unfortunately you will not be able to see that. My driving habits does not allow me to hit the rev limiter.
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Resonator removed (sounds like a V8 on start up)
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