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Is Something Wrong with my Jeep...
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=1&t=33495		 Page 1 of 1
Author:  j1987 [ Fri Jun 20, 2008 1:27 am ]
Post subject:  Is Something Wrong with my Jeep...
Ok so heres the story, one night i was driving home from work when i all of a sudden i got a slowpoke in front of me, so when i had gotten the chance i had passed him which had gotten my libertys RPM to around about 3500-4000(somewhere in between their) just to pass the person. After i had done that move that one night i feel that my engine does not sound the same anymore. Ive been hearing this light cranking/knocking like noise coming from, which i believe its the engine engine. Now this noise is not very noticeable and if i were to take to some mechanic they would probally look at me like im nuts. But since the fact that i drive the car everyday i know what the engine sounds like. But one thing is that i cant belive that just passing a person this one time can do anykind of harm. I mean its not like i redlined it. My Liberty is a 2005 and only has 36,000 miles on it. Im actually starting to think that i just beat in the engine more or something. Again its not like its very loud at all and their is no point in taking the car in becuase its not really that noticeable.
Author:  jeepskate [ Fri Jun 20, 2008 2:27 am ]
Post subject: 
Revs at that level shouldn't do any damage to your engine, but anything's possible. It's next to impossible for anyone to assess it without hearing the noise.
Author:  Fulltimer [ Fri Jun 20, 2008 2:30 am ]
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Have you checked to see if it has thown a code? It's a place to start.

Terry
Author:  detroit_doc [ Fri Jun 20, 2008 8:09 am ]
Post subject: 
I hit 9,000 RPM in my Honda S2000 at least twice a day for 3 years. I probably hit 4,000 RPM once a day in my Liberty pulling onto the freeway with a short on-ramp and heavy traffic. The engine is designed to work up to the redline without fear of damage.

Your noise is probably unrelated to the 4,000 RPM you pulled.

Vehicles are complex with a lot of parts. Your noise could be something as simple as a loose heat shield or an exhaust leak. Noises related to internal engine problems are usually rythmic and rise and fall with engine RPM (tapping, ticking, knocking, etc). Serious engine problem are usually also accompanied by other problems (driveability problems, rough idling, smoking, check engine light illumination, etc).

So if you noise isn't rythmic and doesn't increase and decrease with engine RPM, and you don't have any driveability issues, no check engine light, no overheating, no oil pressure warning, no smoking or oil usage etc. It's probably just something minor.

If it is a rythmic noise that is coming from the engine and increases and decreases with RPM (while the trans is in neutral/park) then it might be worth having a mechanic look at it. I think there were some reports of faulty valve springs.
Author:  sleeve84028 [ Fri Jun 20, 2008 8:09 am ]
Post subject: 
Step 1: Check the OIL! If it's low - you should add some
Step 2: Check the codes
Step 3: Listen to the motor after it's warmed up. At Idle and then while driving. If the noise stays the same or doesn't get louder as you drive than I would not worry

Step 4: If everything checks out - WELCOME to the -slightly noisy KJ engine club.


Mine sounds like it's going to spit out a rocker but it runs great and the noise isn't too loud. If the noise gets any louder than I'll start to worry. But for the past 6 years, there hasn't been a change in the loudness.
Author:  offroadohio [ Fri Jun 20, 2008 8:48 am ]
Post subject: 
My engine has seen 5000-6000 several times and it runs the same as new, I seriously down you hurt anything hitting 4k, but alot of places will do free vehicle inspections and tell you whats wrong if anything
Author:  KJ4ME [ Fri Jun 20, 2008 2:57 pm ]
Post subject: 
my engine was at about 4800rpm at 75mph for 81 miles and its totally fine
Author:  jason thompson [ Fri Jun 20, 2008 6:05 pm ]
Post subject: 
I am also one who thinks it is just the noisy 3.7 engine
we have hit the rev limiter a few times in the KJ ,maybe 2 or 3
now the TJ has hit the rev limiter countless times and it runs fine
I know guys with over 100K on the I-6 and they dont think twice about hitting the rev limiter
so to do 4K in the KJ would not cause a problem
Author:  tier10 [ Fri Jun 20, 2008 6:33 pm ]
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I've driven many vehicles to date and I've heard a few with a little tiny tapping. Even four wheelers, bikes, you name it. I was just thinking the other day that my 3.7 was making a little tapping noise, something that almost sounds like a fan running on low. Engines either work or they don't. Like others have mentioned, check your oil, if it has oil and your low oil light isn't on your OK, assuming it is running strong with no miss, or loss of power of course.
Author:  tjkj2002 [ Fri Jun 20, 2008 6:37 pm ]
Post subject: 
tier10 wrote:
I've driven many vehicles to date and I've heard a few with a little tiny tapping. Even four wheelers, bikes, you name it. I was just thinking the other day that my 3.7 was making a little tapping noise, something that almost sounds like a fan running on low. Engines either work or they don't. Like others have mentioned, check your oil, if it has oil and your low oil light isn't on your OK, assuming it is running strong with no miss, or loss of power of course.
99% sure that most of your "light tapping" is the injectors firing,the 3.7 has very loud injectors,and the fact that at full operating temp the 3.7 is only speced to have 2-3 psi of oil pressure at idle.
Author:  tier10 [ Fri Jun 20, 2008 6:45 pm ]
Post subject: 
tjkj2002 wrote:
99% sure that most of your "light tapping" is the injectors firing,the 3.7 has very loud injectors,and the fact that at full operating temp the 3.7 is only speced to have 2-3 psi of oil pressure at idle.[/quote]

I learned something today, I was never told that about the injectors. It makes sense now that I think about it. And yes I've only heard it while at idle, however I've noticed it cold and at operating temps.
Author:  offroadohio [ Fri Jun 20, 2008 6:53 pm ]
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I've heard the 2-3psi thing before, and it scares me, I've blown up numerious 3.8 buick, and old cj duantless v6's due to low pressures like that and idling around in the woods.
Author:  tjkj2002 [ Fri Jun 20, 2008 6:53 pm ]
Post subject: 
Quote:
It makes sense now that I think about it. And yes I've only heard it while at idle, however I've noticed it cold and at operating temps.
Not to sound like a smart @ss but the injectors fire when the engine is cold or hot when it's running.
Author:  tier10 [ Fri Jun 20, 2008 7:33 pm ]
Post subject: 
tjkj2002 wrote:
Quote:
It makes sense now that I think about it. And yes I've only heard it while at idle, however I've noticed it cold and at operating temps.
Not to sound like a smart @ss but the injectors fire when the engine is cold or hot when it's running.


LOL Right, I know that. I was saying it more then likely is the injectors, as you said the oil pressure drops at idle while warm.
Author:  mrkake [ Sat Jun 21, 2008 2:20 am ]
Post subject: 
Same thing happened to me in my Volvo. It has twin turbos and I was messing around with the Geartronic shifter and inadvertently left it in 2nd and stomped the pedal to the floor when I was already doing about 25mph. I went WAY past redline and when I got home I noticed a ticking noise. This engine was so quiet before this that you couldn't tell it was running unless you were outside or looked at the tach. That was about 80,000 miles ago. It still has that little tick and it has been to both dealerships and private mechanics and no one has ever said that it sounded unusual.

What does this all mean in your case? Maybe nothing happened. Or then again maybe it did. I would investigate to a reasonable level and if you don't find anything wrong just get used to it. If you're like most guys you will hear stuff all the time. Every time I do a repair/mod to any vehicle and have "phantom noises and performance quirks" :roll:
Author:  MNKK [ Sat Jun 21, 2008 3:48 am ]
Post subject: 
mrkake wrote:
inadvertently left it in 2nd and stomped the pedal to the floor when I was already doing about 25mph. I went WAY past redline


Just a friendly little kick in the bollocks to get it up and going.
Author:  sleeve84028 [ Sat Jun 21, 2008 10:04 am ]
Post subject: 
offroadohio wrote:
I've heard the 2-3psi thing before, and it scares me, I've blown up numerious 3.8 buick, and old cj duantless v6's due to low pressures like that and idling around in the woods.


The 3.7 has proven to be very reliable though and it was designed to run on very little oil pressure. A very great little motor (save for that valve spring thickness)
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