Question about 1999 Jeep Grand Cherokee

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My jeep has a knocking sound coming from the engine and makes the same clicking/knocking sound when I'm accelerating what could this problem be?

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Noisy lifters, or piston slap, i just had one where the piston went through the block, try on your next oil change putting a liter of tranny fluid in it with the oil, the better lubrication will settle a noisy rocker

Posted on Mar 24, 2011


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Makes knocking noise that sound like something is loos banging only when jeep warms up and only in gear

1. PISTON SLAP: Makes a sharp metallic noise. Idle engine and short out each cylinder plug. The noise will disappear when plug with bad piston is shorted. Noise will also disappear at acceleration. This can be caused by worn or out of round cylinder, or broken piston ring. Correct problem by re-boring cylinder and/or replacing piston.
2. VALVE NOISE: Makes clicking or rattle noise. Caused by excessive wear on valve stem or lifter, out of adjustment, or stuck valve. Correct by adjusting valve clearance, replace worn valve or lifter, regrind cam, replace valve guide and /or valve. A stuck valve can sometimes be loosened by passing oil through the carburetor while engine is running.

3. ROD BEARING KNOCK: Makes sharp metallic noise similar to a piston slap. Detection is opposite of piston slap. Rod knock is not heard at idle. Knock becomes louder as engine speed is increased. Caused by excessive rod bearing clearance. Correct by adjusting rod bearing clearance to .0015 inches by removing shims. May require re-pouring rod bearing.
4. REAR MAIN BEARING KNOCK: Makes dull knocking or thud noise. Detected at speeds between 20 and 50 MPH. Knock will normally decrease or disappear while pulling or decelerating. Noise will be detected the loudest at normal driving speed, when not pulling or decelerating. Correct by adjusting bearing clearance to .001 to .0015 inches. If knock is excessive, crank should be checked for out of roundness. May need to re-pour all main bearings to correct.
5. TIMING GEAR KNOCK: usually the most difficult to diagnose. If gear is loose or badly worn it will knock in all ranges. Run engine slightly above idle speed. Slowly open and close throttle. Knock will continue to be present, but just as engine slows down knock will become a slight rattle. Remove timing pin and reinsert into timing hole on timing gear cover. Press timing pin tightly against timing gear and accelerate slightly above idle. Knock will significantly be reduced or disappear. Correct by replacing both timing gear and crank gear as a matched set. The two gears should have a backlash clearance of .003 to .004. If more than .009 inch backlash, an oversize (.005) timing gear should be installed.
6. WRIST PIN SLAP: This can not be detected by shorting out the cylinder plugs. Rapidly accelerate and decelerate the engine speed. The engine will pass through a certain speed range when the wrist pin will rattle at about the same pitch as a valve tappet noise. This can be corrected by installing a new wrist pin bushing in the rod or new wrist pin f badly worn. Wrist pin should fit the piston and connecting rod with a tight metal to metal fit. The pin can be pushed into the piston and rod with a slight pressure of the hand. Pin to rod clearance is .0003 to .0005 inches.

Dec 07, 2013 | Jeep Cars & Trucks

1 Answer

Knocking noise and bad shaking

sounds like the engine need s some going over have it checked out

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My 1997 Ford Explorer Eddie Bauer v8 AWD makes a really deep ticking/clicking sound when running. It's hard to describe the sound, but it's almost as if you can hear each piston cranking. As I accelerate...

It could be rod knock: if so, plan on an engine change/rebuild. On my 97 F 250, 5W motor oil is recommended,so you can't put in heavier oil. But that's not a solution. Something mechanical is askew.

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1 Answer

1993 jeep cherokee 4.0 HP I am having a knocking sound during acceleration under load. Also with the a/c on during throdling up the engine quickley is also knocks. Whats up is this detination, What...

hi i think my last post was lost for some reason., but here it is again, the knocking sound you can hear is probably the big end bearings worn, these are the shells that go between the conrod and the crank shaft , it sounds like they have worn either by lack of oil at some time, or just through age and use, this is also normally accompanied by low oil pressure light coming on but not always, 2 options you have are, another engine, or repair the bearings , but this will depend on how bad the crank has been damaged by the worn bearings..hope this helps please vote and rate thanks

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1 Answer

I have a 5 speed Jeep Wrangler. When decelerating the jeep has a knock. When accelerating there is still a slight knock but not nearly as loud and without the vibration. When i put it into neutral the jeep...

check the driveshaft end joints (check when not in tension) and check for excessive play in the differential yokes. Aside from up and down play make sure they do not turn excessively before wheels begin to turn. If you find no problems there then you may have a transfer case problem. End joints fail far more frequently than do transfer case internals or differentials (unless you run them low on lube) So it's a good idea to check them before worrying about large items.

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1 Answer

I hear a knocking in the motor

not very specific, however, if it really loud, that may suggest internal engine damage...not good. also, if it sounds more like clicking which gets faster/slower depending on the speed of the engine, that would be you lifters = check oil = ensure correct level. or, switch to proper grade of oil if you have deviated from what the manufacturer recommends. it would help if you could tell me exactly where the "knocking" sound is coming from and what the vehicle is doing when you here the noise. oh, if it makes a knocking/pinging sound when you are under heavy acceleration or going up a steep hill (high load) check your spark plugs and try using a little bit better gas....

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3 Answers

Audible knocking in rear of 1993 jeep grand cherokee laredo with 150,800 miles knocking only occurs when accelerator is not pressed

Sounds as If You Have A Chipped Tooth On the "RING GEAR" in the Differential (Rear Alex).
Is this Where You Hear The Noise Coming from? If So Remove Diff Cover With One Wheel OFF The Ground Trans In Neutral Rotate Drive Shaft and Look Closely For ANY Abnormal Surface on EACH Tooth of RING GEAR= the Large one And The "PINION GEAR" the Small one. If you find Chip or Rough spot Diff Must Be Rebuilt. Beyond that A Pinion Bearing can Also Make A Knocking Noise But the "GEARS" Will Be a Rhythmic Noise. I Hope this is of Some Help To You Good Luck !!

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From your description i would say that you have lost/spun a rod bearing and have a rod "knocking" against the block.
I would stop driving the vehicle immediately.
if you are able to do it yourself i would pull the oil pan and look for pieces of bearing.

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Lou,I belive your right.When an axle goes this is the sound they make.

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