Mastermind007

Got a 2004 Grand Cherokee with the IL6. I haven't had it long, about 3 months and noticed a tapping when cold that goes away once I start driving.
When I first start it up in the morning it does not do it. But after roughly a minute or so it should like the values are clattering. Attached is an audio file I recorded using my phone this morning.
https://drive.google.com/file/d/129f...ew?usp=sharing

The oil level is fine and since I got it from my parents and they bought it new I know the history and it has always had 5W30 in it. Oil changed every 3000 miles like clockwork as well as all the suggested preventative maintenance (my parents are obsessed with that).
Nothing major just normal wear and tear items (brakes, plugs, etc...

Once I start driving, usually to the end of the driveway ( a couple hundred feet) the tapping goes away. Rans great, oil pressure is perfect, idles smooth and does not skip a beat when accelerating.

For the life of me I just an not figure this one out. Any help/guidance would be appreciated.

Chuck

blueseasons

This probably isn't a big factor but factory spec is 10w-30 for the I6. You need to find out if the noise is coming from the top end or lower. I can't open the link. Its either a gummed up part or a worn out part.

00t444e

I couldn't open the video, but from your description it sounds like the normal 4.0 lifter tick.

extrashaky

Go by Harbor Freight or Sears and pick up a mechanic's stethoscope. The HF one is $4. Then poke around with it until you find what's making the noise. Ticks and taps can come from the motor, but they can also come from other places, like the cam position sensor and the evap purge solenoid (does the Grand Cherokee have one of those like the XJs?).

dave1123

The one major defect in the construction of the 4.0 is the lack of a valve lash adjustment. There is none, so once the valve train parts start to wear, it rattles. It is nothing to be concerned about.

If it goes away and doesn't return as long as the engine is warm, it could be piston slap.

Mastermind007

Thank for all the feedback.

The file a linked was just an audio clip I took with my phone so no video.
I did the old broomstick test. Next time I run by Harbor Fright I will grab a mechanic's stethoscope. The tapping it just under the value cover towards the front.

One other thing I noticed is from a cold start on a 28 degree day it does it for able 3-4 minutes than just stops. The tapping does not soften or slowly get quieter, it just quits. The tap does speed up if you give it a little throttle so it is tied to the RPM of the engine.
So to recap. Start the engine (when it is cold out), it runs for about 30 seconds to a minutes without any tapping at all. then the tapping starts. In three more minutes to just stops. The whole time the engine never hesitated or fluctuated in any way.

There is also another tap from a solenoid mounted to the driver side fender well with a rubber cushion. It is much quieter and does it all the time. I had read in another post someone mentioned that so I just wanted to clarify it is not that component that is the source of the tapping in question.

blueseasons

You can do better than a broomstick. Use a piece of heater hose or similar until you get a stethoscope.

Bugout4x4

The lifter still has oil from having been run then shut off so at first it is quiet. Then right after you start it cold it pushes this oil out of the lifter before the lifter has oil to it again and clicks. Then when the oil does get to it it gets quiet again. There is a delay from when the oil gauge shows pressure and when the lifters finally get pressure.

This is normal in a lot of engines. In a big rig it takes almost a full minute for the last main bearing to actually get pressure even though it showed pressure on the gauge. This is why when a driver revs up a truck engine right after it starts you go yank him out of the truck and fire him. lol

dave1123

I was going to do an experiment on my 4.0 by grinding .020" (.5 mm) off the bottom of the valve rocker pivots to add a little more preload to the lifters, but it would be time consuming and expensive to do on my DD, so it never happened. Another option was to replace all the pushrods, rockers, and pivots with new ones or use a thinner head gasket.

Because this is a normal occurrence with a 4.0, it didn't seem to matter enough to be worth the effort. My engine rattles constantly at idle unless you hit the highway for a short time, then it's quiet until you shut it off again. It seems to me it takes time for all the parts to grow with temperature to stay quiet.

97grand4.0

As Dave knows, I have been chasing the same problem with my 200k 6 banger all summer. I have replaced rockers and pushrods, timing chain, all really to no avail. Quiet at first then as it warms up starts to sound like a diesel, then that goes away after a few minutes. I have come to the conclusion that it is piston slap, a rather benign condition well documented, seems the skirts were made short to allow faster rpms with less weight. Jeep is aware of the problem and made my pistons with teflon skirts, thus the rather dull knock sound. Mine has done it the whole 50 k I have owned it.
Two things that did help but not cure it. One was the most recent thing I did, replace the TPS. Yes the tps. On scan tool it was 17.5 % on idle stop, and the pattern would spike down on the scope (drop out) randomly. So changed that and thought my gas gauge was stuck when it didn't drop down like so fast as it has been, but no just better performance, leaner mixture at start up.
Other thing that seemed to help also was top end cleaning.

After thought: One reason the TPS could be suspected is if it is sensing the throttle open at idle more than it actually is, as happens when the bottom end of the tps potentiometer is worn from constant feathering of the gas pedal, it is telling the pcm that the throttle is open and the pcm advances the timing as well as richens the mixture.

dave1123

Oh...Yeah....Every time I put a can of Seafoam in the tank, it runs and idles smoother until that tank is gone! Then it slowly gets lumpy and stupid after a while.

When I changed the cylinder head, there was a lot of carbon in the intake manifold and on the back of the intake valves. That is caused by oil vapor coming thru the CCV system. That can be reduced by adding an oil catch can (google it) to filter out any oil that may come from the crankcase. It seems turbo cars have a problem with this carbon breaking off and destroying turbo blades. An airline water separator should work and I'll install it as soon as I find it in my garage junk!

Hey "97", the slipper pistons are there because of the long stroke. They would hit the crank if not modified. They do rock a bit which causes the skirts to fail. Now that you mention it, a tapping that goes away during warmup and doesn't come back until cold may just BE piston slap!

97grand4.0

I am leaning (get it, LEANing?) towards a carbon problem more than piston slap. After I replaced the TPS I saw huge changes in the way it starts and runs. Much more efficient. Also had dumped a whole bottle of seafoam in the cylinders and let it set overnight. Left it right in the oil and drove it. End result is it runs so much quieter after the tps, not the resonating roar sitting at a stoplight. Not a slingshot out of the hole either, but fuel mileage is so much better that I thought my gas gauge had stuck

Bugout4x4

I have the part number for a slightly longer pushrod Dave. These cured the rattle in mine. But more importantly, I found that the bridges and pivot pedestals twist and become misaligned with the valve stem. This causes the pushrods to try and push the rocker sideways instead of inline vertical like it is supposed to. These could use heavier bridges to keep them straight.

97grand4.0

I did the new sealed power rods, bridges, pivots, and rockers over the summer chasing the rattle, as well as timing chain and water pump. I can say for sure the rattle is now gone. I will add that I am tickled pink about it too. It was the tps causing rich misfire and fuel map, which may have lead to coking the valves and rings. New tps and a lot of seafoam ..but poured in the plugs holes as well as the usual top end stuff.
I would be very hesitant to change the stock valvetrain geometry.
Those bridges, the trick is to tighten them when the valve is fully closed..especially when the other valve is also closed...with a torque wrench, and only slowly.

Bugout4x4

The pushrods I replaced mine with were only a few thousands longer. But realigning the rockers along with these slightly longer pushrods did the trick. Twisting the rockers and alignment bridges back where they belong was the main improvement though. Changing out the pushrods cured most of them but I had a few that were still rattling, I then noticed these few rockers were twisted out of alignment with the pushrods and valve stems. So I twisted them and the bridges back into line with the "push". The rattle completely stopped and has been gone since I did this.