I have a 2000 cherokee sport 4.0 with 173000 miles and about 4000 miles ago it the engine started tapping when it was cold. Two days ago it went from a lite tapping when cold to an all out knock all the time, the knock is louder than the tapping was but it is still a loud tapping sound. Any ideas as to what it could be?
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Re: 2000 jeep cherokee sport engine knock
First you got to determen where its comming from, surley you can hear if its comming from top of engine or from oil pan, i'am not there to hear it so its hard to tell what it is, but i can take some gusses on what it could be. You said a while back it started tapping, that could be a loose or woren rocker or lifter does it run on all cyls. no miss, good oil pressure, could be a connecting rod. The millage is high and things do wear out.
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well either your lucky and you have an exhaust leak (very common on the 4.0 jeep engines) or you have a collapsed lifter, bad wristpin,spun bearing...and other assorted bad mojo.. if it is a 4.0 its very common for them to have exhaust leaks due to the long cast iron manifold. its also common for them to have noisey lifters once they get up there in millage. i have a 2000 jeep and the lifters on it have been making noise for about 40 thousand miles and i havnt had any issues with it. just went to a slightly thicker grade of oil. hope this helps
I am assuming you have the 5.2 liter (318 cubic inch) V-8. If the knocking is coming from the oil pan, you may be able to just replace the main and rod bearings on the crankshaft and the oil pump. It is a relatively simple but messy job dropping the pan. I did that job on my old Dodge Dart Sport 318 when it had about 150,000 miles. After I installed the 0.001" under sized bearings, the knocking went away and the oil pressure was back to where it was supposed to be. Make sure the crank surfaces are not damaged or you will be wasting your time. If you end up replacing the engine, the cost will depend on if you get an engine from the junk yard, buy a crate engine, or have the original engine rebuilt, and could run between $1000-3500.
When the pressure reads low, are you hearing any knocking or tapping noises from the engine? If so, you may have worn engine bearings. I'd check the actual pressure by having a mechanical gauge installed on it in order to determine the actual pressure (your gauge is electro-mechanical and not quite as accurate) If pressure is actually that low the oil pan must be removed and bearings, oil screen etc need to be checked. The reason pressure is always higher at first is that when cold the oil itself is thicker...as it gets hot and thins out pressure will drop somewhat, but should not go that low. Only other thing that can affect pressure in that way would be either a bad sending unit (you will know that after testing) or gasoline contamination in oil (happens if an injector is not working properly) Good luck with it!
Two things...when it reads zero, is there any engine noise (tapping or knocking)? After you rev the engine does the pressure read normal at idle and function normally, or does it go back down? Either way, you should not drive the vehicle 'till you have a mechanical gauge (yours is electro-mechanical) put on there and the actual pressure is tested. The condition may be a bad sending unit, a bad bearing or possible obstructed oil pump screen. The repair is obviously different for each one and the price is as well.
Did you try changing the air breather for the motor?You need three things inorder for the engine to run well. Air,fuel,and spark.since you had a tune up and fuel flushed.I can only think of two things.First I never heard of flushing a fuel filter,you change it ( not flush it ) change your fuel filter,eliminate the guess work.And change your breather.
A few questions for you how many miles on the engine? have you had regular oil changes done? This model should have the 4.0 liter engine if so what you are describing sounds like rod knock. The 4.0L engine is designed to take allot of abuse and last for well over 200,000 miles but if regular oil changes are not done you are in for trouble. And the only way to fix rod knock to have the engine rebuilt.