Hammering / knocking noise on 4.0L6 '99 Cherokee
 

I would say, I have a severe case of piston slap, but from what I have
found out about the infamouspiston slap problem, it should have ended
long before 1999.
So, what problem do I have on my '99 Cherokee? The symptoms are very
similar to the legendary piston slap:
Symptoms vary from no noise, to a light ticking, to a
ticking/hammering to a
strong and very audible hammering/knocking noise. The noise is
generally more pronounced at start up, when the engine is cold.
Sometimes, the noise disappears when the engine warms up.
Sometimes, when the noise appears at start up, stopping and
immediately restarting the engine stops the noise completely.
The symptom is most noticeable during idle, but will get louder as
engine speed increases, and sometimes appears / disappears randomly on
a warm engine and at various driving conditions.
While this noise was very infrequent before, now it is a almost daily
occurrence.

The engine has about 60K and was serviced regularly at the local
dealer, with
oil and Mopar filter changes every 3,000 Miles. The engine runs,
starts,
and idles otherwise completely fine. No significant oil consumption
either.

The dealer here in Thailand suggests to open up the engine, and
perhaps change the hydraulic lifter, but he is basically not really
sure, what causes the problem.

I have used a Fuel Injector Cleaner without success.

Most likely, it is not the piston slap problem, as the car is built in
1999.
If it is the lifter, why stopping and restarting the engine clears the
noise
immediately sometimes, but not all the time.
The noise appears at a cold engine and on a warm engine as well, and
during idle but during normal driving conditions as well, but
randomly, it seems. If drive at high rpm, there is generally no noise.

What could cause that noise?

Any help from you old timers and experts would be greatly appreciated.

Re: Hammering / knocking noise on 4.0L6 '99 Cherokee
 

Interesting....

The last time I heard those symptoms was on the first start up of a
fresh rebuild and we both just about ---- ourselves we were so pissed
off. We restarted it and no noise or low, then creeping back up. 3rd
time knock knock.

Then as we are leaning over to try and listen where it was coming from,
I put my hand on the alternator and almost got burned it was so hot.
Bingo, the alternator had decided to give up and something inside was
slamming around.

We then used an automotive stethoscope to confirm it. Basically a thin
metal rod with a clear plastic hose on one end. The hose goes to the
ear and you can really trace down a knock with one.

I would be making or using one before spending money. Even your finger
touching parts can sometimes nail it.

One other cause of a strange knock is a worn clutch on the rad fan.
This can change every start up and usually is temperature dependent as
the clutch changes when hot.

With the engine cold and off, I would try moving the rad fan around for
play or clicks.

I would then heat it up good and watch when someone shuts down the
engine. If the fan keeps spinning after a hot shutdown, the clutch is
baked. It should stop almost immediately.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Robert Goldpalm wrote:
>
> I would say, I have a severe case of piston slap, but from what I have
> found out about the infamouspiston slap problem, it should have ended
> long before 1999.
> So, what problem do I have on my '99 Cherokee? The symptoms are very
> similar to the legendary piston slap:
> Symptoms vary from no noise, to a light ticking, to a
> ticking/hammering to a
> strong and very audible hammering/knocking noise. The noise is
> generally more pronounced at start up, when the engine is cold.
> Sometimes, the noise disappears when the engine warms up.
> Sometimes, when the noise appears at start up, stopping and
> immediately restarting the engine stops the noise completely.
> The symptom is most noticeable during idle, but will get louder as
> engine speed increases, and sometimes appears / disappears randomly on
> a warm engine and at various driving conditions.
> While this noise was very infrequent before, now it is a almost daily
> occurrence.
>
> The engine has about 60K and was serviced regularly at the local
> dealer, with
> oil and Mopar filter changes every 3,000 Miles. The engine runs,
> starts,
> and idles otherwise completely fine. No significant oil consumption
> either.
>
> The dealer here in Thailand suggests to open up the engine, and
> perhaps change the hydraulic lifter, but he is basically not really
> sure, what causes the problem.
>
> I have used a Fuel Injector Cleaner without success.
>
> Most likely, it is not the piston slap problem, as the car is built in
> 1999.
> If it is the lifter, why stopping and restarting the engine clears the
> noise
> immediately sometimes, but not all the time.
> The noise appears at a cold engine and on a warm engine as well, and
> during idle but during normal driving conditions as well, but
> randomly, it seems. If drive at high rpm, there is generally no noise.
>
> What could cause that noise?
>
> Any help from you old timers and experts would be greatly appreciated.

Re: Hammering / knocking noise on 4.0L6 '99 Cherokee
 

Interesting....

The last time I heard those symptoms was on the first start up of a
fresh rebuild and we both just about ---- ourselves we were so pissed
off. We restarted it and no noise or low, then creeping back up. 3rd
time knock knock.

Then as we are leaning over to try and listen where it was coming from,
I put my hand on the alternator and almost got burned it was so hot.
Bingo, the alternator had decided to give up and something inside was
slamming around.

We then used an automotive stethoscope to confirm it. Basically a thin
metal rod with a clear plastic hose on one end. The hose goes to the
ear and you can really trace down a knock with one.

I would be making or using one before spending money. Even your finger
touching parts can sometimes nail it.

One other cause of a strange knock is a worn clutch on the rad fan.
This can change every start up and usually is temperature dependent as
the clutch changes when hot.

With the engine cold and off, I would try moving the rad fan around for
play or clicks.

I would then heat it up good and watch when someone shuts down the
engine. If the fan keeps spinning after a hot shutdown, the clutch is
baked. It should stop almost immediately.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Robert Goldpalm wrote:
>
> I would say, I have a severe case of piston slap, but from what I have
> found out about the infamouspiston slap problem, it should have ended
> long before 1999.
> So, what problem do I have on my '99 Cherokee? The symptoms are very
> similar to the legendary piston slap:
> Symptoms vary from no noise, to a light ticking, to a
> ticking/hammering to a
> strong and very audible hammering/knocking noise. The noise is
> generally more pronounced at start up, when the engine is cold.
> Sometimes, the noise disappears when the engine warms up.
> Sometimes, when the noise appears at start up, stopping and
> immediately restarting the engine stops the noise completely.
> The symptom is most noticeable during idle, but will get louder as
> engine speed increases, and sometimes appears / disappears randomly on
> a warm engine and at various driving conditions.
> While this noise was very infrequent before, now it is a almost daily
> occurrence.
>
> The engine has about 60K and was serviced regularly at the local
> dealer, with
> oil and Mopar filter changes every 3,000 Miles. The engine runs,
> starts,
> and idles otherwise completely fine. No significant oil consumption
> either.
>
> The dealer here in Thailand suggests to open up the engine, and
> perhaps change the hydraulic lifter, but he is basically not really
> sure, what causes the problem.
>
> I have used a Fuel Injector Cleaner without success.
>
> Most likely, it is not the piston slap problem, as the car is built in
> 1999.
> If it is the lifter, why stopping and restarting the engine clears the
> noise
> immediately sometimes, but not all the time.
> The noise appears at a cold engine and on a warm engine as well, and
> during idle but during normal driving conditions as well, but
> randomly, it seems. If drive at high rpm, there is generally no noise.
>
> What could cause that noise?
>
> Any help from you old timers and experts would be greatly appreciated.

Re: Hammering / knocking noise on 4.0L6 '99 Cherokee
 

Interesting....

The last time I heard those symptoms was on the first start up of a
fresh rebuild and we both just about ---- ourselves we were so pissed
off. We restarted it and no noise or low, then creeping back up. 3rd
time knock knock.

Then as we are leaning over to try and listen where it was coming from,
I put my hand on the alternator and almost got burned it was so hot.
Bingo, the alternator had decided to give up and something inside was
slamming around.

We then used an automotive stethoscope to confirm it. Basically a thin
metal rod with a clear plastic hose on one end. The hose goes to the
ear and you can really trace down a knock with one.

I would be making or using one before spending money. Even your finger
touching parts can sometimes nail it.

One other cause of a strange knock is a worn clutch on the rad fan.
This can change every start up and usually is temperature dependent as
the clutch changes when hot.

With the engine cold and off, I would try moving the rad fan around for
play or clicks.

I would then heat it up good and watch when someone shuts down the
engine. If the fan keeps spinning after a hot shutdown, the clutch is
baked. It should stop almost immediately.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Robert Goldpalm wrote:
>
> I would say, I have a severe case of piston slap, but from what I have
> found out about the infamouspiston slap problem, it should have ended
> long before 1999.
> So, what problem do I have on my '99 Cherokee? The symptoms are very
> similar to the legendary piston slap:
> Symptoms vary from no noise, to a light ticking, to a
> ticking/hammering to a
> strong and very audible hammering/knocking noise. The noise is
> generally more pronounced at start up, when the engine is cold.
> Sometimes, the noise disappears when the engine warms up.
> Sometimes, when the noise appears at start up, stopping and
> immediately restarting the engine stops the noise completely.
> The symptom is most noticeable during idle, but will get louder as
> engine speed increases, and sometimes appears / disappears randomly on
> a warm engine and at various driving conditions.
> While this noise was very infrequent before, now it is a almost daily
> occurrence.
>
> The engine has about 60K and was serviced regularly at the local
> dealer, with
> oil and Mopar filter changes every 3,000 Miles. The engine runs,
> starts,
> and idles otherwise completely fine. No significant oil consumption
> either.
>
> The dealer here in Thailand suggests to open up the engine, and
> perhaps change the hydraulic lifter, but he is basically not really
> sure, what causes the problem.
>
> I have used a Fuel Injector Cleaner without success.
>
> Most likely, it is not the piston slap problem, as the car is built in
> 1999.
> If it is the lifter, why stopping and restarting the engine clears the
> noise
> immediately sometimes, but not all the time.
> The noise appears at a cold engine and on a warm engine as well, and
> during idle but during normal driving conditions as well, but
> randomly, it seems. If drive at high rpm, there is generally no noise.
>
> What could cause that noise?
>
> Any help from you old timers and experts would be greatly appreciated.

Re: Hammering / knocking noise on 4.0L6 '99 Cherokee
 

Hi Robert,
If it ever sounds like a ticking then I vote with your dealer and
say you need a new set of lifters. But if it does sound like a hammer
beating the side of the block, then it could be piston slap, but usually
that won't go away with oil pressure and warm up, and will at a certain
RPM be more pronounced. I think your describing main bearings, their
worn clearances let the oil drain out during the time it sits, and
knocks until they are lubed again. I think it time to take it apart and
find the problem while you still have a core.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Robert Goldpalm wrote:
>
> I would say, I have a severe case of piston slap, but from what I have
> found out about the infamouspiston slap problem, it should have ended
> long before 1999.
> So, what problem do I have on my '99 Cherokee? The symptoms are very
> similar to the legendary piston slap:
> Symptoms vary from no noise, to a light ticking, to a
> ticking/hammering to a
> strong and very audible hammering/knocking noise. The noise is
> generally more pronounced at start up, when the engine is cold.
> Sometimes, the noise disappears when the engine warms up.
> Sometimes, when the noise appears at start up, stopping and
> immediately restarting the engine stops the noise completely.
> The symptom is most noticeable during idle, but will get louder as
> engine speed increases, and sometimes appears / disappears randomly on
> a warm engine and at various driving conditions.
> While this noise was very infrequent before, now it is a almost daily
> occurrence.
>
> The engine has about 60K and was serviced regularly at the local
> dealer, with
> oil and Mopar filter changes every 3,000 Miles. The engine runs,
> starts,
> and idles otherwise completely fine. No significant oil consumption
> either.
>
> The dealer here in Thailand suggests to open up the engine, and
> perhaps change the hydraulic lifter, but he is basically not really
> sure, what causes the problem.
>
> I have used a Fuel Injector Cleaner without success.
>
> Most likely, it is not the piston slap problem, as the car is built in
> 1999.
> If it is the lifter, why stopping and restarting the engine clears the
> noise
> immediately sometimes, but not all the time.
> The noise appears at a cold engine and on a warm engine as well, and
> during idle but during normal driving conditions as well, but
> randomly, it seems. If drive at high rpm, there is generally no noise.
>
> What could cause that noise?
>
> Any help from you old timers and experts would be greatly appreciated.

Re: Hammering / knocking noise on 4.0L6 '99 Cherokee
 

Hi Robert,
If it ever sounds like a ticking then I vote with your dealer and
say you need a new set of lifters. But if it does sound like a hammer
beating the side of the block, then it could be piston slap, but usually
that won't go away with oil pressure and warm up, and will at a certain
RPM be more pronounced. I think your describing main bearings, their
worn clearances let the oil drain out during the time it sits, and
knocks until they are lubed again. I think it time to take it apart and
find the problem while you still have a core.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Robert Goldpalm wrote:
>
> I would say, I have a severe case of piston slap, but from what I have
> found out about the infamouspiston slap problem, it should have ended
> long before 1999.
> So, what problem do I have on my '99 Cherokee? The symptoms are very
> similar to the legendary piston slap:
> Symptoms vary from no noise, to a light ticking, to a
> ticking/hammering to a
> strong and very audible hammering/knocking noise. The noise is
> generally more pronounced at start up, when the engine is cold.
> Sometimes, the noise disappears when the engine warms up.
> Sometimes, when the noise appears at start up, stopping and
> immediately restarting the engine stops the noise completely.
> The symptom is most noticeable during idle, but will get louder as
> engine speed increases, and sometimes appears / disappears randomly on
> a warm engine and at various driving conditions.
> While this noise was very infrequent before, now it is a almost daily
> occurrence.
>
> The engine has about 60K and was serviced regularly at the local
> dealer, with
> oil and Mopar filter changes every 3,000 Miles. The engine runs,
> starts,
> and idles otherwise completely fine. No significant oil consumption
> either.
>
> The dealer here in Thailand suggests to open up the engine, and
> perhaps change the hydraulic lifter, but he is basically not really
> sure, what causes the problem.
>
> I have used a Fuel Injector Cleaner without success.
>
> Most likely, it is not the piston slap problem, as the car is built in
> 1999.
> If it is the lifter, why stopping and restarting the engine clears the
> noise
> immediately sometimes, but not all the time.
> The noise appears at a cold engine and on a warm engine as well, and
> during idle but during normal driving conditions as well, but
> randomly, it seems. If drive at high rpm, there is generally no noise.
>
> What could cause that noise?
>
> Any help from you old timers and experts would be greatly appreciated.

Re: Hammering / knocking noise on 4.0L6 '99 Cherokee
 

Hi Robert,
If it ever sounds like a ticking then I vote with your dealer and
say you need a new set of lifters. But if it does sound like a hammer
beating the side of the block, then it could be piston slap, but usually
that won't go away with oil pressure and warm up, and will at a certain
RPM be more pronounced. I think your describing main bearings, their
worn clearances let the oil drain out during the time it sits, and
knocks until they are lubed again. I think it time to take it apart and
find the problem while you still have a core.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Robert Goldpalm wrote:
>
> I would say, I have a severe case of piston slap, but from what I have
> found out about the infamouspiston slap problem, it should have ended
> long before 1999.
> So, what problem do I have on my '99 Cherokee? The symptoms are very
> similar to the legendary piston slap:
> Symptoms vary from no noise, to a light ticking, to a
> ticking/hammering to a
> strong and very audible hammering/knocking noise. The noise is
> generally more pronounced at start up, when the engine is cold.
> Sometimes, the noise disappears when the engine warms up.
> Sometimes, when the noise appears at start up, stopping and
> immediately restarting the engine stops the noise completely.
> The symptom is most noticeable during idle, but will get louder as
> engine speed increases, and sometimes appears / disappears randomly on
> a warm engine and at various driving conditions.
> While this noise was very infrequent before, now it is a almost daily
> occurrence.
>
> The engine has about 60K and was serviced regularly at the local
> dealer, with
> oil and Mopar filter changes every 3,000 Miles. The engine runs,
> starts,
> and idles otherwise completely fine. No significant oil consumption
> either.
>
> The dealer here in Thailand suggests to open up the engine, and
> perhaps change the hydraulic lifter, but he is basically not really
> sure, what causes the problem.
>
> I have used a Fuel Injector Cleaner without success.
>
> Most likely, it is not the piston slap problem, as the car is built in
> 1999.
> If it is the lifter, why stopping and restarting the engine clears the
> noise
> immediately sometimes, but not all the time.
> The noise appears at a cold engine and on a warm engine as well, and
> during idle but during normal driving conditions as well, but
> randomly, it seems. If drive at high rpm, there is generally no noise.
>
> What could cause that noise?
>
> Any help from you old timers and experts would be greatly appreciated.

Re: Hammering / knocking noise on 4.0L6 '99 Cherokee
 

Could the cause of this problem be found
within the electronic / contact / sensor input complex?

Today, no noise at all, so far. No noise at cold start,
no noise during normal driving conditions with a warm
engine. No noise whatsoever.

So, if it would be a purely mechanical problem such as
piston slap, hydraulic lifters, or carbon build up, why is
there no noise today?

I am living in the tropics (Thailand) with a very high humidity
of around 80-90%. Could it be, that somewhere, an electronic
contact or a wrong sensor input causes the engine to produce
this ticking / knocking sounds sometimes?

Re: Hammering / knocking noise on 4.0L6 '99 Cherokee
 

Could the cause of this problem be found
within the electronic / contact / sensor input complex?

Today, no noise at all, so far. No noise at cold start,
no noise during normal driving conditions with a warm
engine. No noise whatsoever.

So, if it would be a purely mechanical problem such as
piston slap, hydraulic lifters, or carbon build up, why is
there no noise today?

I am living in the tropics (Thailand) with a very high humidity
of around 80-90%. Could it be, that somewhere, an electronic
contact or a wrong sensor input causes the engine to produce
this ticking / knocking sounds sometimes?

Re: Hammering / knocking noise on 4.0L6 '99 Cherokee
 

Could the cause of this problem be found
within the electronic / contact / sensor input complex?

Today, no noise at all, so far. No noise at cold start,
no noise during normal driving conditions with a warm
engine. No noise whatsoever.

So, if it would be a purely mechanical problem such as
piston slap, hydraulic lifters, or carbon build up, why is
there no noise today?

I am living in the tropics (Thailand) with a very high humidity
of around 80-90%. Could it be, that somewhere, an electronic
contact or a wrong sensor input causes the engine to produce
this ticking / knocking sounds sometimes?