Expensive sounding engine noises

The last few months of driving my good old Cherokee with a 4.0 engine and about 300,000 miles has been making a bit of a clicking sound when the engine is cold. Tonight as I was driving along the clicking sound got a lot worse, and the engine was hot.

As this engine has a BUNCH of miles on it I'm really afraid it might be a rod bearing letting go, but I'm hoping it might actually be a lifter. The noise is now always there, and it seemed to be getting worse as I drove, it is somewhere between a click and a clatter. The oil pressure is at least good enough the idiot light stays off, and of course the crankcase is full. Under moderate to heavy acceleration the noise goes away, it's always there under light acceleration and when cruising or idling.

Is there a quick and dirty check? I seem to recall if you pull the spark plug wires off one by one and the problem really is a bad rod bearing it will quiet down when that cylinders wire is pulled, but if it's a lifter pulling wires won't make any difference.

If it is the rod bearings what kind of luck have you guys had with used engines vs rebuilt. I have neither the money or the inclination to buy a new Jeep and plan to keep this one for as long as I can. (Well, a new Wrangler Unlimited with a hardtop would be really cool, but that's only going to happen if the Prize Patrol shows up!).

Jeff DeWitt

Jeff DeWitt did pass the time by typing:

Hot as in operating temp or hot as in overheated?

It's gonna tick even without the cylinder working since spring force is what pushes the lifter back. Valve slap (broken/weak valve spring) can be detected that way though. Not that a real bad lifter/rod can't be detected, but the noise they make is a "deep noise" low in the block and on the spark plug side.

Your less likely to shock the piss out of yourself by simply taking the fuel injector connection off.

The 4.0 uses valve guides that can be replaced without taking the head off. But you need compressed air to keep the valves in place.

Sure it isn't a cracked exhaust manifold? A hairline crack will seal as the header expands and does a real good job of sounding like lifter tick.

Rebuilt 4.0's are all over the place. There is no difference between a quality rebuilt and a new engine.

I'd still check the exhaust manifold first.

No, the engine was hot as in througly warmed up, not overheating.

Robb, I belive your right about valve noise vs lower engine noises... and I've got a really bad feeling about this.

I'm going to do the stethiscope thing and see what I can hear, but I think I'm going to be buying an engine.

Anybody know anything about these guys?

Collapsed lifter, perhaps? For a while I had an `82 Malibu with the V-6 that would make horrible loud death-coming-soon whacking noises every once in a while, always while hot, always in hot weather -- this a few months after my `79 CJ had spun a rod bearing on my way to work (the motor kept turning just long enough to get off a busy interstate and into to a commuter parking lot). As the Malibu was my only ride at the time (and I was broke) it scared the bejeasus out of me the first couple of times it happened. Apparently it was a gummy lifter that would come and go at will. I got another 30K out of that motor.

Jeff DeWitt wrote:

I don't know anything about this site, but the prices look great. Perhaps they would be willing to give you the phone numbers/email addresses of some owners/mechanics that have purchased from them so you call and ask their opinion of their rebuilds.

cal