4.0 rocker problem

Yesterday, i was on the way back from doing some work with CSudman and his friends when my jeep crapped out on me. driving down the street, gradually a noise that sounded like the lifters were crappin out on me came up, then the jeep died.

after coasting to a stop, i restarted the engine and from what i could tell, the clacking noise was comming from the top, front of the engine around the 2 or 3 cylider. it was decided to have the heep towed home.

today, i cracked the valve cover off in hopes of finding the problem. both rockers on number 1 and one of the rockers on cylinder 2 have a lot of play in them. I broke out the torque wrench and gave the bolts a twist to 19 ft-lbs as it says in the manual and they still didnt tighten up.

ok, here are the questions-

first, would loose rockers cause the jeep to die while driving or should i be looking for another problem?

next, could a lifetime of of ware on the rocker cause it to be loose even when torqued correctly or is it because of a problem deeper in the block?



If the symptoms i listed sound like any other problems anyone has had, let me know, or if i am heading in the wrong direction with my investigation.

First thing I´d check, is to see if 1 or 2 or both arn´t firing. Did the motor pick up a heavy miss, before it crapped out? A cylinder that isn´t firing, will get pretty loud. Clatter and clack.
If it seems to be firing, I´d check the top of the push rods, for oil when the motor is running, you can usually see the oil squirt out tof the top of the push rod, in dabs and dribbles. If your not getting oil to the top of the push rods, don´t run the motor long. What´s your oil pressure look like?
Most of the pressure on the push rods, comes from oil pressure (at the lifters). have seen the push rod ends and the push rod seat in the rocker, pretty worn. But most times this won´t affect the motor running much, just gets loud.
Don´t have the oiling diagram for the 4.0 or the 4.2, but guess they are generaly the same as most other motors. Crank gets oil first, then the lifters.
Have seen lifters go bad, eather the oil orifice plugged or the retaining clip breaks and the insides, pop out. But usually just on one lifter. Have seen cams, become seriously worn and whole layers of material wear off (looks ugly).
If more than one lifter is involved, chances are it is an oiling problem, a cam problem or a bearing problem on the crank (blocking/interfering with oil circulation).
Push rods are often pretty loose, when a cylinder is at the top of the compression stroke. I generally don´t worry about it much, unless it is really excessive.

Depending on where the particular cylinder is within its 4 stroke cycle, the rocker may not be snug against the spring and the pushrod may have some slop in it.

For the rockers to cause the engine to not run, multiple of them would have to be in pieces. Sounds more likely that you are seeing a normal condition on the rockers but something else is the issue.

Tom's rule #1: troubleshoot, don't blindly start throwing parts at a problem and hope one of them fixes it.

My first step in a situation of this type is to eliminate the easy things. Check the oil. Verify the oil pressure. Check that there is fuel pressure at the injector rail with it running.

If it runs but runs rough, start by pulling and replacing the spark plug wires one at a time. If there is a cylinder that has problems, you will see less of a rpm drop on that cylinder. If they are all the same, you can rule out a single plug, wire, or injector.

If one is different then take the next step and again check the simple things. Pull the spark plug and make sure it looks OK. Swap it with a plug from a different cylinder. Did the problem migrate to a different cylinder? If so you have a bad plug. If not, swap spark plug wires. Did the problem follow the wire? If not, your problem is most likely not ignition.

If you have a cylinder miss and it isn't the ignition, it is either compression or a lack or excess of fuel. Probably the easiest thing to do is to check the compression. If it is OK, the problem is a fuel problem. Try swapping two adjacent injector plugs. It will not run optimally, but at an idle, things should be OK for testing. Did the problem follow the injector connector? If not the injector drive from the ecu is most likely OK, but there is no guarantee.

Ideally, now swap two injectors. If the problem does not follow the injector, you have screwy ECU problem or more than likely more than one problem.

The point of this whole exercise is to do some simple troubleshooting by changing things around and paying attention to what happens. I see far too many people giving a list of $300 worth of sensor and things they have changed and never fixed the problem.

NCSUcherokee said:

Yesterday, i was on the way back from doing some work with CSudman and his friends when my jeep crapped out on me. driving down the street, gradually a noise that sounded like the lifters were crappin out on me came up, then the jeep died.

after coasting to a stop, i restarted the engine and from what i could tell, the clacking noise was comming from the top, front of the engine around the 2 or 3 cylider. it was decided to have the heep towed home.

today, i cracked the valve cover off in hopes of finding the problem. both rockers on number 1 and one of the rockers on cylinder 2 have a lot of play in them. I broke out the torque wrench and gave the bolts a twist to 19 ft-lbs as it says in the manual and they still didnt tighten up.

ok, here are the questions-

first, would loose rockers cause the jeep to die while driving or should i be looking for another problem?

next, could a lifetime of of ware on the rocker cause it to be loose even when torqued correctly or is it because of a problem deeper in the block?

If the symptoms i listed sound like any other problems anyone has had, let me know, or if i am heading in the wrong direction with my investigation.

Click to expand...

Two loose rockers would definitely cause the engine to die simply because it cannot run on only four cylinders. When the rockers are loose, they cannot open the valves so the cylinders affected can't produce any power.
The question is why the rockers should come loose. This can happen if they haven't been torqued down correctly after a head rebuild but that doesn't apply in your case.
Since your rockers are patently worn out, the only possible reason is an oiling problem so I think you need to start looking there. If the oil pressure is OK, that'll rule out oil pump and bearing wear. The rockers are oiled through the pushrods and lifters. If the oil passages in either of these are blocked by dirt, the oil won't reach the rockers.
I suggest that you pull off all the rockers and inspect them for wear. Keep them numbered so that you put them back in the same place they came from. Do the same for the pushrods and check if the oiling holes are patent. If they are, you'll have to pull off the head and inspect the lifters.
Let us know what you find. If you do end up removing the head, you might wanna think about porting it, rebuilding it, and maybe installing a performance cam with new lifters (provided you've found the source of the oiling problem).

thanks guys, i will start from there

one more thing, This engine has had chronic problems with overheating and from the feel of the oil that is pooled in the rocker arms there could be some heavy chunks of carbon floating around inside so a blocked oil passage would not supprise me.

Aside from changing the oil more often, how can i clean out all the carbon and sludge from the passages without blowing out all of the seals and gaskets?

If you got it too hot you could have burnt a hole through the piston. Test as Old Man suggested - good advice there. Once that problem is corrected then fix the overheating issues before it leads to more or new problems. Good Luck.

Woody

got into the rockers after work today, to find exhaust rocker on 1 wasnt getting oil, so i fixed the problem, checked all the parts and re-assembled, even though by the time i put it back together i knew that wasnt the problem. Right from the start i noticed the noise didnt get louder when i took the valve cover off.

so i will start tommorow looking for a different problem

the engine has oil pressure, it idles decently smooth (as smooth as it ever has) and isnt missing any cylinders. it just clicks. at higher RPM the click turns into a rattle almost or maybe it is just indistinguishable clicks.

more info if you want to make an educated guess

-as said the noise stays the same with the valve cover off
-it is almost the same loudness top to bottom of the engine, though slightly louder on the drivers side
-all the valves run smooth

If this happened suddenly...something...well...happened suddenly...Noisiest on drivers side? Maybe a busted exhaust manifold...a bad leak on one cylinder can make a sound a lot like ticking...check all your accessory drives and idlers check the waterpump bearings...if you have an auto tranny..pull the inspection cover and see if the converter or flexplate bolts are loose...if you have a manual tranny and the clutch or release bearing had a problem you would most likely feel it in the clutch pedal.

The overheating thing is scary...do as suggested and get a baseline on the engine condition...compression test as a minimum...I highly recommend a cylinder leakdown test...Any good radiator shop can pressure test the motor and do a hydrocarbon test on the coolant to see if you have a headgasket leak or cracks in the water jackets. good luck.