oh boy

[RBrandon]

It's desicion time... My 98 grand cherokee 4.0 liter has what sounds like a collapsed valve spring only it's coming from the engine block and not the head.
I pulled the volve cover and turned the engine over a few times and the valves work fine, the oil pumps fine, and the push rods seem to work fine. So if the springs are good and all of the keepers are in place and it's getting oil up top then that puts me in unfamiliar territory. I assume it has hydraulic lifters being a modern engine and I didn't see any way to adjust valve lash which I assume is preset in the lifter (from what I have read). Because the noise is related to one cylinder firing (this I know from a few dealings with single valve spring issues in the past) I feel it has to be something wrong with a lifter. Only I don't know much more about them, save that the push rod sits in the lifter.

My question is this: my engine is about to roll 280k (not 180 but 280...) Is is safe to assume I have reached the upper service life of this engine and retire it or should I replace the lifters and trudge on? I could probably find one in a local salvage yard fairly cheap and slap it in. I just don't want to drop the money only to discover that my problem could have been fixed in a few days worth of shade tree work and then run for a good while longer. The engine doesn't burn any oil between changes and I have ran mobile 1 full synthetic since around 85k miles. My problem is down time and free time and the fact that taking the engine apart is an exploratory deal in which I don't know how many parts (can, pistons, etc.) will need replacing. Not to mention it would be a shame to break it down that far and not rebuild it properly. I may just replace it with a used one and rebuild the old one in my spare time as a practice run before I rebuild my mustang in the future. Any thoughts on the noise and / or the amount of life left in this engine are appreciated.

[hardisk_c]

Is it a knocking noise coming from within the block at all RPM's or does it cut out if you rev/idle?


I know this is from a Sattie instead of a Jeep, but if this is similar in sound, your prolly looking at a rod knock in that engine.
Sattie w/ rod knock

Just my

[dksob81]

a collapsed lifter would cause a knock as well, you would have seen this when you had the valve cover off. you would have seen slop in the rocker arm.

[RBrandon]

Update: I am leaning towards a lifter. If anything, at 5 bucks a pop from OReileys I can replace all 12 and if that isn't it then I won't cry too much. Now I just need to find my manual and see if I can pluck the little buggers out through the head without having to pull it. Part of my reasoning is that the engine runs great and doesn't eat oil... yet. I would like to reach 300k so that I can feel like Crysler (not to mention Amsouth) didn't ream me too bad when I bought the thing. (long since payed off, but still the dreams come...)

[RBrandon]

Well, I purchased a short block from Masterbilt motors in Birmingham and pulled my engine out today. My old engine came out without too much hastle but I realized I had the wrong engine as soon as I stripped mine down and started trying to put parts on the new block. The block looks the same roughly but some holes aren't tapped out that need to be and at TDC on #1 the cam lobes don't seem to be the same. At any rate, I now get to take both blocks back Monday (a day I took off to make sure I had a long weekend for this little project) and either the guy will have the right block or I will just let him rebuild mine. Oh, and I also checked my new hydraulic lifters and one never charged up. Heck, that could have been the problem all along but with 280k miles I figure a new engine is in order. I am trading my tools this evening for a stiff jack and coke (repeated until my frown goes away, which sadly doesn't take much...) opcorn: Catch you all later. Wish me luck.

[RBrandon]

Note, I left a gap in there... I replaced the lifters and had the head reworked before my previous entry and while I was happy to see that everything worked the same, I was not happy to see that everything worked the same. Noise didn't go away. That is why I mentioned the one lifter not charging up. All of the new ones I pulled out could not be compressed but one could still be pushed in via finger and thus was not acting lilke a solid. Since the noise was still present I sent my wife off to find me a short block and a place called masterbilt motors (I could only assume they were part of the nationwide chain...) had one for 600 dollars. Heck. I should have payed the 1777 at advance auto for a ong block. There, now you have the whole story.