Well we did some more detailed testing today and came up with some confusing results. We were able to amplify the sound by using a makeshift mechanic’s stethoscope and prodded all around the engine. When the engine is in park and in neutral, there is a pretty distinct metal on metal click like sound. Revving the engine just increased the speed of the clicking so it’s definitely related to the RPM. The confusing part was that as soon as I put the car into drive, the clicking instantly became much louder. We tracked the noise down to the very rear of the engine, which is probably why I could hear it so clearly in the cabin. Does info point to a lifter problem, and if so, why does it instantly become so much louder as soon as I put the car in drive?
As VDC pointed out these inline 6’s are known for lifter noise… I’d put a quart of Rislone in the crankcase to see if you can get the offending lifter to “pump up”…It usually works quite well actually…Give it a shot
The reason a sticking lifter get louder when under load has to do with just that…Load… If it was an exhaust valve lifter that was lagging…the late opening of the exhaust valve would be harder to open bec the piston was already on the way up…and expecting a valve to already be opened…the lagging valve is then at that moment harder to open…which amplifies the noise… I could write a thesis as to the WHys of it all… Just try to free up that lifter by using a “Rislone type of solvent” in your crankcase
Try a quart of “Rislone” They have been around since the 50’s or longer and always have been proud of their lifter quieting potential…I have used it with success in the past… Give it a shot…bout 5 bucks… You can drop a quart of oil b4 putting it in or add it on top of your oil already present.
Blackbird
I’m really not trying to beat a dead horse here, but these manifolds crack at the rear, down low near the flange if I remember. If it is cracked there, the noise would instantly become louder in drive because the engine rocks toward the passenger side in drive while the exhaust pipe wants to stay stationary, making the crack ever so slightly larger.
Have an assistant power brake the engine while you run your hands along the exhaust manifold downpipes feeling for hot exhaust escaping.
Tomorrow we will take out a quart of oil and replace it with Rislone and see if it helps. We’ll also examine the exhaust manifold more carefully because I don’t want to rule anything out just yet. Examining the manifold will be pretty tricky though as I don’t really want to accidentally touch the hottest part of the engine. I’ll post results as soon as we pour in the Rislone and take if for a drive around to give it a chance to clean out the lifters.
If the Jeep is raised and the splash guard removed the exhaust manifold can easily be seen from under neath. Pouring a few teaspoons of motor oil or transmission fluid into the throttle will cause enough smoke to make an exhaust leek evident. Of course, do this with the engine cold, have a good flashlight and use a good jack stand or rest the left front tire in the spare to be safe.
Yeah Ase has a point…but I was taking your word for it when you say you hear a “clapping or a tapping” The tapping is almost always a stuck lifter making too much clearance between the rocker arm and the top of the valve…this open space allows the rocker to “hammer” the valve top…this is the clicking or tapping sound…
To those not initiated in all these noises…I can see someone confusing lifter tapping with a cracked exhaust manifold…but I would be able to tell the diff right away…so ASE’s suggestion does have merit…and is good knowledgeable advice…check that out also…it makes a sort of similar sound…to me it doesn’t but I can see someone else mixing them up…
*** "While I nodded, nearly napping, suddenly there came a tapping,
As of some one gently rapping, rapping …PERHAPS…You have a Raven or a Honda Blackbird under your Bonnet? LOL Its time to stop thinking when you start to quote the Raven when diagnosing a car problem…I think I may be going Nuckin Futs…
Blackbird
It can be as frustrating for us, as we try to “read” the OP’s meaning as it is the OP as (s)he looks for meaningful advice. Blackbird. Until reading Ase’s post I had forgotten that the 4.0L often cracked the exhaust manifold and for the uninitiated the noise could be confused with a mechanical tapping. Is there some way to put an audio on this forum?
Yup…those 4.Oh’s do love to crack the exhaust manifold… Now to me and probably you…this noise is nothing like a loose rocker arm…but it does have a sharp sound and is in synch with the engine/rocker arm issue…so to the newbies…yeah maybe they think the leak sound it a tapping…
I just got out of my car after starting it on this relatively cold day. I’m convinced that it is a lifter problem, the tapping was loud and definitely metallic. I’ll be replacing a quart of oil with the Rislone, that was recommended earlier, later on today. Hopefully it will at least reduce the noise.
Yeah man, give it a shot…Rislone has worked for me in the past…When I knew it was a lifter and not a rocker…OR a slightly bent or improperly seated valve. If it doesn’t…it is NOT that hard to swap out the 12 lifters that you have…
Before you get there, and if the Rislone doesn’t work after 2-3 wks…Pull the valve cover and make sure to examine ALL your rocker arms…you may have a cracked rocker on the offending noisemaker…if it has cracked and lost its rigidity then it will flex and make the clearance that makes the noise… So check those rockers…this is important…
Also look at your valves…they all need to be at the same seated height…meaning…one should not be lower than another…if it is…then it is slightly “hung”…could be carbon deposits…could be bent…more likely carbon… When this happens with carbon, I loosen the rocker and rotate it out of the way…I usually lightly “tap” the valve top with a hammer this will make the valve seat HARD…much harder than the camshaft will allow…this will break up most carbon hanging issues…after that the valve seats properly and the noise goes away due to no excess clearance.
If the Rislone doesn’t work…and then you check all the rockers…and find all of them perfect… You can then replace only the lifter that is making the noise…or all of them… They’re cheap and rather easy to do. If you get to this point…remember to soak all the lifters in 30W or lighter oil overnight so they can drink in the oil and “pump up” Then install.
Let us know how the Rislone works or doesn’t work…I would add it ON TOP OF the oil you presently have in the crankcase…being 1qt overfull wont hurt you in this engine…or you can drain 1/2 a Qt out…I like to be full or overfull when doing this lifter resurrection process. You now have your next steps if “The Riz” doesn’t do it…I’d give the Rislone at least a week…as many as a 3-4wks to work…
ALSO if you are afraid to accidentally touch the HOT Exhaust manifold you can use a piece of paper…run the paper along the manifold and see if it flutters…if it does you found the leak. You can also use mechanics Nitrile or latex gloves…you wont get burned as fast using these…
Blackbird