Jeep knocks on startup, then goes away. - Page 2 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > WJ Grand Cherokee Forum > Jeep knocks on startup, then goes away.

Savvy Billet LED Tail LightsLight up the holidays with LED lights from JeepHutIntroducing MONSTALINER™ UV Permanent DIY Roll On Bed Line

Reply
Unread 08-06-2011, 01:56 PM   #16
billzcat1
Chicken in a Turkey Suit
2003 WJ 
 
Join Date: Oct 2008
Location: Redmond, WA
Posts: 8,537
I dunno, maybe since it is posted in here 2-3 times a week. Compared to 2-3 times a year someone posts with a blown-up 4.7.

billzcat1 is offline   Reply With Quote Quick reply to this message
Unread 08-06-2011, 03:27 PM   #17
skiebuster
Registered User
2004 WJ 
 
Join Date: Aug 2009
Location: Argos, Indiana
Posts: 140
I would bet that its a cracked piston skirt. Mine did it for 80K miles....it was more noticeable with a fresh oil change. It would come and go, meaning it didn't do it every time on start up. When it started knocking the last time, it did it for 20 miles, then stopped, then did it all the way home from from a field trip.
Next morning I went for coffee and while heading to work, it tapped hard for 10 seconds and the vacuum went. I drove it 8 miles to my shop, parked it and found a 2006 wrangler 4.0 to replace it. My 4.0 had a hole you could place yur fist in....sat for 2 months for me to get ready to swap engines. It started up and drove it into my shop...needless to say, my dad and I were stunned!


We have replaced 3 of the 4.0 engines, all from piston skirts letting go. If its knocking, pull it and slap some really good pistons in it.
skiebuster is offline   Reply With Quote Quick reply to this message
Unread 08-06-2011, 03:29 PM   #18
skiebuster
Registered User
2004 WJ 
 
Join Date: Aug 2009
Location: Argos, Indiana
Posts: 140
Quote:
Originally Posted by billzcat1 View Post
I'm guessing cracked piston. It's far more common in 4.0s than the 4.0 fans would have you believe.
I agree...read my post! the 99 and up WJ 4.0's have poor skirt design. I bet the factory made them thinner for several reasons...cost, faster revs, MPG and so that the dealer will replace it for a ton of money down the road. lol
skiebuster is offline   Reply With Quote Quick reply to this message
Unread 08-06-2011, 03:41 PM   #19
shockracer
14,000' WJ
 
shockracer's Avatar
2001 WJ 
 
Join Date: Oct 2010
Location: Northern, Colorado
Posts: 1,643
Drop your oil pan and have a look, not to pricey to do and you can inspect everything else.
__________________
2001 WJ 60th anniversary edition 4.7 quadra-drive
5" hybrid lift, 265/70/17 Guard Dogs load E, bilsteins 5100's, addco sway bars, JKS front quick disco's, JKS adjustable track bar, KOR durometer track bar bushings, IRO crucial path front L.A.s, 1.25" Spidertrax spacers

Colorado Jeep Club Member #262
shockracer is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.