Question about 1999 Jeep Grand Cherokee Limited

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Jeep 4.7 V8 Knock under hood

This is driving me insane, I have a knock in the engine but only when warm, starts up quiet and gets louder as it heats up. Replaced lash adjusters as thats where it seemed to come from, no difference. Dropped the pan as much as I could and managed to find number 8 rod bearing flapping around, replaced it, no difference. While valve covers were off inspected timing chain and it looks brand new as do the guides (the ones I could see) Compression is at 140 apart from 1 and 7 at 135. Temperature constant at 210. Oil Pressure at idle is at half and goes to just under 3/4 when driving. LOADS of power! Unlike other posts I have seen on the interweb mine starts in the morning perfect but a couple of miles down the road the knock starts and does not stop until it has been cooled down. Any help very much appreciated.

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  • Jeep Master
  • 3,655 Answers

It would be unlikely the number 8 rod bearing would be flapping around without causing some damage to the finish of the crankshaft journal.

The big question is why was it flapping around in the first place? Often a shortage of oil being supplied to that bearing would be the cause and the main suspect.

I suggest you revisit that bearing and take a closer look and maybe use a micrometer to check that journal.

Posted on Mar 16, 2017

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Posted on Jan 02, 2017

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stormbrewin
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SOURCE: knock from valve cover

Sounds like lifter not pumping up or worn out but you may also have tight valves by that i mean over time the valves sink into the head and sit tightly on the rocker arm.You really should take cover off to check noise in case a rocker adjust nut or something else isnt coming undone.While you have the cover off check all the valve clearances,You may find that it will idle a lot better if the valves open and close at the right time.It is very thin oil what was manufacturers recomendation?

Posted on Oct 20, 2008

bitchn65cuda
  • 70 Answers

SOURCE: One morning when I headed to work, I noticed a

what is the millage of your car? what was the last oil change? diagnosing your car would be your lifters....

Posted on Apr 26, 2009

landsend
  • 1066 Answers

SOURCE: no/low oil pressure, high engine temp

I think you have a bad ground on your engine gages...but, more importantly, have your oil pressure checked by a mechanic.  If it is indeed only 20 pounds the engine is sadly on it's last legs.
When you receive advice from this website you have to understand that without the item in front of us, we are only able to provide "a best guess" as to what the problem might be based on you description of the defect.  If you haven't described a clear and precise description of the defect you decrease the chances of an accurate reply.  Thank you.   

Posted on Apr 28, 2009

  • 109 Answers

SOURCE: 1999 Jeep Grand Cherokee overheated

You probably messed up a rod or caused piston damage your going to need more than a head gasket usauly when you over heat a car you causing the pistonts to expand more then they need to causing scouring and exsisive piston ware by the sound of it and the year your better off replacing the whole motor or completely rebuilding the old one wich will cost more then a use motor! good luck!

Posted on Sep 12, 2009

Testimonial: "good advice, easily understood, and written very clearly. thanks"

charleshucke
  • 1114 Answers

SOURCE: Have 2001 jeep Cherokee classic 4.0l. At idle the

This could be caused from a few different things, so lets start with the simplest thing first. Since you are certain that there is not a knock in the engine, I would start by changing the oil and substitute a quart of oil and use a can of Seafoam in its place. This will clean the engine and any oil build up that has occurred over the years. I would then recommend changing the oil filter; make sure that you get one that has a check valve in it, so you will not have a dry start. You mentioned that the engine is chattering, and that is not a good sign. This means that parts, probably lifters, are not getting properly lubricated, and that may be the sign of a bad pump. I know that you stated that you have changed it, but, there is a chance that it is faulty. Before you do that, I would recommend that you put a live oil pressure gage on the engine to see what pressure you are holding. The engine should hold 20-40 psi at an idle. The 10 psi that you are getting is not sufficient, and if this goes unresolved, then you are looking at some serious internal engine damage.

Posted on Mar 16, 2011

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