mjeff87 Posted March 19, 2014 Share Posted March 19, 2014 2.5 in my TJ has recently developed a pronounced ticking/clacking sound on cold startup, under engine load. After about 2-3 minutes of driving it goes away, so I'm thinking it's a bad lifter (as opposed to a rod bearing). Frequency is consistent with upper end rotation as well. If I pulled the lifters and could identify a bad one(s), would it be advisable to replace just the bad one or replace them all? And if replacement is warranted, is a camshaft change absolutely necessary? I've read conflicting info on the interwebs ranging from "new lifters on old cam" is ok (but not visa-versa) to "OMG you'll trash the cam in 10 seconds flat". Engine has @ 186K on it, and otherwise runs like a top. 40 psi oil pressure at hot idle, 50-ish while driving. WWCCD? (What would Comanche Club do) TIA, Jeff Link to comment Share on other sites More sharing options...
Jeepman Posted March 19, 2014 Share Posted March 19, 2014 In my Experience you should change the cam as well if doing the lifters but your problem is more likely the Rocker arms themselves as they are a wear item and cheap to replace over doing the cam and lifters... I would start with the rocker arms and go from there... Good luck in whichever way you decide... Link to comment Share on other sites More sharing options...
jimoshel Posted March 19, 2014 Share Posted March 19, 2014 I always recommend replacing both and on a customers engine I always do. However on my own engine I have used the old cam-lifter if after a careful inspection and measuring showed no wear. Do as I say. Not as I do. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 20, 2014 Share Posted March 20, 2014 In my Experience you should change the cam as well if doing the lifters but your problem is more likely the Rocker arms themselves as they are a wear item and cheap to replace over doing the cam and lifters... I would start with the rocker arms and go from there... Good luck in whichever way you decide... I would try this first too Jeff. The rocker arms are about $7/ea, and both the 2.5 and 4.0 use the same p/n, J3242393. If no joy, I'd then have a good shop rebuild the head. Link to comment Share on other sites More sharing options...
mjeff87 Posted March 20, 2014 Author Share Posted March 20, 2014 Thanks all. Maybe I'll pull the valve cover this weekend and take a look at the top end stuff. I've had the head on this engine off twice now, once to repair the rear exhaust stud and most recently due to a head gasket leak/replacement. Maybe it's possible one of the rocker studs loosened up (had that happen on the 2.5 that used to be in my MJ, the rocker actually slipped off the pushrod). I'm just curious why the sound only happens under cold load (not at idle) and goes away after a couple minutes of driving. Jeff Link to comment Share on other sites More sharing options...
Jeepman Posted March 20, 2014 Share Posted March 20, 2014 The noise is very common on the I6 and I4 and is probably just due to the lifter bleeding off a little more then others and needing to load up... Normally it is not an issue worth chasing as I have installed a brand new cam and lifters and rocker arms and the tick has came back again... Link to comment Share on other sites More sharing options...
Eagle Posted March 20, 2014 Share Posted March 20, 2014 2.5 in my TJ has recently developed a pronounced ticking/clacking sound on cold startup, under engine load. After about 2-3 minutes of driving it goes away, so I'm thinking it's a bad lifter (as opposed to a rod bearing). Frequency is consistent with upper end rotation as well. If I pulled the lifters and could identify a bad one(s), would it be advisable to replace just the bad one or replace them all? And if replacement is warranted, is a camshaft change absolutely necessary? I've read conflicting info on the interwebs ranging from "new lifters on old cam" is ok (but not visa-versa) to "OMG you'll trash the cam in 10 seconds flat". Engine has @ 186K on it, and otherwise runs like a top. 40 psi oil pressure at hot idle, 50-ish while driving. WWCCD? (What would Comanche Club do) TIA, Jeff I would do some more investigating. Think about how an engine works. A lifter does not know whether or not the engine is under load. The only thing a lifter knows is that there's a cam lobe pushing up on the bottom, and a pushrod pushing down on the top. And there's some oil being pumped into it. The oil pressure varies with engine RPM and oil temperature but it, too, doesn't know if the engine is under load. So if your noise is really only there under load, I'd say it probably is not a lifter. I would also say that Jeep engines often have some valve "tick" on cold start-up, especially as the mileage increases. I think if it were mine I'd be inclined to leave it alone. Link to comment Share on other sites More sharing options...
Eagle Posted March 20, 2014 Share Posted March 20, 2014 I'm just curious why the sound only happens under cold load (not at idle) and goes away after a couple minutes of driving. Jeff Exhaust manifold leak? That usually makes a tick. As it warms up the metal expands and the gap closes. Link to comment Share on other sites More sharing options...
mjeff87 Posted March 21, 2014 Author Share Posted March 21, 2014 No manifold leak, it's a brand new unit (old one was VERY cracked). I did snug up the manifold bolts, too. The tapping seems to be getting more consistent now. I'm pulling the VC and plugs tomorrow morning, going to check each rocker/pushrod/lifter to see if I can find any slop anywhere. Link to comment Share on other sites More sharing options...
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