Engine Noise-Taping valves

Hi
I have 2000 Cherokee 4.0L 77K miles Automatic Transmission
I bought this car last November. Car runs almost perfect, if not for noisy valves.
First when I start my jeep everything runs well. After about 10 min into street driving engine’s valves start to tap.

The valve noise happens when Engine water temp is in normal operating temps 210 deg. Oil pressure at idle is 15-19 psi, and at cruising, oil pressure is at 45psi. Valve noise starts at exactly 2000 rpm’s and continues until engine’s revolution reaches around (but less than) 2500rpm’s .
Valve noise goes away with increase in rpm (above 2500rpm), or if transmission shifts to next
gear and rpm’s drop to nice 1300-1600 rpm. There is no noise during idle or cruise. It only happens when engine is well wormed up and accelerating from 2000 to 2500 rpm.

When engine first started engine oil pressure is at nice 50 to 55 psi, and after a few minutes water temp gets to nice 200-210 deg. During that time, there is no valve noise for about 10 min
(10 min is summer 20 min in winter)

It looks like lifters are not getting enough pressure to get that zero valve clearance. When engine is cold, all the clearances between engine case and lifter –tappet body are smaller, and by that more oil gets to lifter, and maybe that’s why there is no valve noise during that time.

I have this problem since I purchased it last November. I have tried different grades of oil. 10W-30, 10W-40, 20W-50, and now 5W-30. There was no change in oil pressure when used10-W30, and 40.(valve noise continued). But when I had used 20W50 oil pressure increased, valve noise got smaller and it sounded better, but never went away completely. Currently I am using 5W30, and it got even worst. I have to switch back to that 20W50 I guess.

I did not use synthetic oil. Don’t want to loosen up old carbon deposits and screw up all the bearings. But maybe good clean up of that engine what be a good idea.
I don’t want to take heads off.

Maybe there is something else I can do? Did anyone had the same problem before?

Thanks for the info. Klimo

I have a slight tap in my 96 but only when ideling or until engine gets to around 180-195 then cant hear it. But we recently changed my head gaskets(off road overheating) really sucked but anyway i think i just over looked a push rod when torqueing them down and dident tighten it up enough.

might want to take valve cover off and see if there all tight

Sounds like a good idea; a loose valvetrain would rattle.

But I'm confused by the 2000-2500 rpm thing...odd that it would only be loud enough at those engine speeds. Maybe it's only loud at those speeds, loug enough to be heard, and at different speeds isn't audible.

Thanks for reply

I probably don’t hear tapping noise above 2500, just because everything moves so fast, and the frequency of a tap is so high I can’t hear it anymore.
From what I have noticed it looks like I need more oil pressure during that spool up time. When engine is cold and first started oil press. is above 50psi around 55, and everything runs like it supposed to do. When I switched to 20w-50 I helped with oil press., and reduced that noise problem. I don’t know if should use that oil . It is more viscous oil, and maybe not as good as other thinner specially for starting. I will try to take valve cover off next week and will take a look at rockers. I don’t want to go any dipper than valve train, but I will if I have to. Maybe oil pump is a problem. Other than that car runs perfect. Car has good acceleration, so what ever it is with that noise is not affecting performance. So maybe I will let it be the way it is. It is annoying noise, and I would like to fix it . But will see .

Again Thanks For Reply

Klimo

I'm not one to use or promote the use of the vast stock of pour in elixirs that will cure just about any engine ailment but..... you might just have a good old fashioned sticking valve or lifer. If it were my XJ, I would first start with an engine flush (comes in a quart can); follow it's directions (the idea being to clean the oil pickup screen and remove some possible oil pan sludge). Next would be an oil change using a good oil filter (PureOne or Lee or NAPA Gold...*not* Fram) and the correct 10W30 oil. Buy a can of lifter cleaner (CD, Alemite, etc) and add it to the oil (might even try adding 2 cans). As an alternative, you could add a quart can of Marvel Mystery Oil. Run this for 1K or so and repeat the process. See what happens.....

mike