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:
> 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.

Hot as in operating temp or hot as in overheated?

> 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.

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 **** out of yourself by simply taking
the fuel injector connection off.

> 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!).

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.

--
DougW

get yourself a stethascope, and place it in the engine compartment. Go hi,
Go low. that'll answer your question....

DougW wrote:
>Jeff DeWitt did pass the time by typing:
>> 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.
>
>Hot as in operating temp or hot as in overheated?
>
>> 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.
>
>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 **** out of yourself by simply taking
>the fuel injector connection off.
>
>> 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!).
>
>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.
>


--
Message posted via http://www.carkb.com

It would seem to me that the clicking noise would be faster with the valve
train, and slower with the bearing noise. You might even have piston slap
going on. That's wear of a cylinder and a piston is slopping around. That
stephascope will really help you pinpoint it, and also, pay attention to the
frequency of the noise.....valve train= twice as often in RPM Cransk= RPM
or a slower noise.......
Anyone else???? AM I right or just a couple toooooo many beers?

Robb S wrote:
>get yourself a stethascope, and place it in the engine compartment. Go hi,
>Go low. that'll answer your question....
>
>>Jeff DeWitt did pass the time by typing:
>>> The last few months of driving my good old Cherokee with a 4.0 engine
>[quoted text clipped - 35 lines]
>>
>>I'd still check the exhaust manifold first.


--
Message posted via CarKB.com
http://www.carkb.com/Uwe/Forums.aspx/jeep-cars/200507/1

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:
> 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