Cold Engine Piston Slap

[jg45]

Just curious if anyone else is having what I think is piston slap. Since this weekend, it has been getting below 50 degrees at night. When I first start the KJ in the morning, I let it idle for just a minute or two while I wipe the frost/dew off the windows and then drive off. I hear a distinct knocking noise when accelerating that is tied to RPM and load. After just a few minutes of driving, it fades away. I feel pretty certain that this is piston slap. Is anyone else having this? I am still under the 7/70 powertrain warranty and am thinking I may need to take it in to the dealer.

 

[Nursecosmo]

How many miles on engine? Have you also considered valve noise? Here is a thread which might interest you.
http://forums.jpmagazine.com/70/6569433/jeep-driveline/37l-kj-engine-issue/index.html

 

[fulltimer]

How many miles on engine? Have you also considered valve noise? Here is a thread which might interest you.
http://forums.jpmagazine.com/70/6569433/jeep-driveline/37l-kj-engine-issue/index.html

Interesting thread. They seem to be typical of some other Jeepers I know of. They have a very tired engine that needs replaced. It isn't the KJ, it's that particular engine. Could happen to any type of Jeep.

Terry

 

[jg45]

Engine has just a bit over 65K on it. That is why I am wondering if I need to take it in to the dealer. It does not sound like valvetrain noise at all. I am running synthetic 5w30 oil in it.

 

[Nursecosmo]

My brother threw a valve just like the ones in the above thread with about 65k on the clock. If you do a Google search you will find that it is a common problem with the 3.7L engines. It is unfortunately not just a mater of a tired engine.

 

[fulltimer]

The engine in the above link has 153K miles on it:

" The engine has 153K on it. The first time it happen he took it to a local garage and he put it back on and told..."

But, no matter how many miles on it, it should be checked out.

Terry

 

[Nursecosmo]

jg45. If it is indeed piston slap there are a couple of things which you can try to diagnose it before taking it to the Scamcanic. This site has a good recommendation in the fourth paragraph from the bottom of the page. http://www.remanufactured.com/Engine_Noise_Diagnosis_101.htm It says this:

" Some guys will use straight pins stuck in the ankle of the wire boots in the distributor. You know. The guys with tattoos and key rings stuck in their eyebrows. Then they touch a grounded jumper wire to each one. If the noise is changed when the plug wire is shorted to ground, you can figure that the problem is in the reciprocating bottom end parts. (piston, wrist pin, connecting rod or connecting rod bearing) The reason the sound changes is that when you short the cylinder plug wire you are stopping the combustion chamber explosions that are slamming the piston downward making the inside of the big end of the connecting rod bang against it's connecting rod journal. Or in the case of piston slap, no explosion changes how the piston is shoved hard sideways against the cylinder wall."

Here is another thing to try out in the morning when cold.

First thing in the morning, start the engine up and run it for 15 seconds while you listen carefully and memorize the sound and it's intensity. Shut it down quickly, pull the spark plugs and put two squirts of motor oil into each cylinder. Reinstall the plugs, fire the engine up again and listen.

If you have piston slap the noise will have been greatly reduced or even eliminated…..for 15 or 20 seconds that is, and then your nightmare noise will come back like a Marine Corps marching band coming toward you in the parade.

 

[Nursecosmo]

The engine in the above link has 153K miles on it:

" The engine has 153K on it. The first time it happen he took it to a local garage and he put it back on and told..."

But, no matter how many miles on it, it should be checked out.

Terry

No, only one of the engines in that thread had 153k on it. The other one about 2/3 of the way down the post has 74 thousand KILOMETERS on the clock, which is only 50k miles. A modern engine with only 153k miles should NOT be considered worn out, and certainly not one with only 50k. The above mentioned valve problem is so prevalent that Jasper Engine Rebuilders adds a higher output oil pump and an updated valvetrain design to all of their 3.7L engines no mater how many miles are on the clock.

 

[FastTRX]

I believe I have the case described in the posted thread. 3 weeks ago my KJ started making a very light sounding ticking noise (not even anything that sounds close to a knock). It ran fine...I drove it home from school, had a few people listen to it and the opinions were the fan clutch was going. It even had play in it making me think this was the problem. So I changed the fan clutch and serpentine belt. Still making the noise after these were changed. Took it to a mechanice, hooked it up to the computer and sure enough I have a valvetrain problem above cyl. #1. Mechanic thinks it's an easy fix, just have to get it in to be fixed. In the meantime I'm commuting in my moms pontiac...blah (but saving money in gas..hehe).

The one thing that disturbs me is the mechanic too believes my engine is sludged. There is no way this is the case. My KJ has around 108K and I change the oil every 3K just like you should. I am the 2nd owner which worries me because I'm not sure what happened in the beginning of its life but it has ran really good since I've bought it. No problems before this. It has routine maintenance and I've not beaten it in the time I've owned it.

Hopefully this problem will be taken care of very soon (I want my Jeep back!)...but I may let the mechanic know that this is a common problem with the 3.7s around 100K. I also will let him know that a bent valve could be the problem too.

 

[Nursecosmo]

The one thing that disturbs me is the mechanic too believes my engine is sludged. There is no way this is the case. My KJ has around 108K and I change the oil every 3K just like you should. I am the 2nd owner which worries me because I'm not sure what happened in the beginning of its life but it has ran really good since I've bought it. No problems before this. It has routine maintenance and I've not beaten it in the time I've owned it.

Hopefully this problem will be taken care of very soon (I want my Jeep back!)...but I may let the mechanic know that this is a common problem with the 3.7s around 100K. I also will let him know that a bent valve could be the problem too.

It seems that the early 3.7s had an inadequate oil pump as well as an intake screen in the sump which was too small for a good flow. It is thought that because the volume is too low, sludge builds up in the low flow areas of the engine and pieces of it later break off, lodging in the small passages of the oil galleys, blocking cooling jets and the intakes for the hydraulic lifters. once that happens there is too much slack between the valve and rocker and it just falls off because there is not any kind of keeper to hold it in place.

FYI my brother developed his problem a short time after running some oil system purge before an oil change. It is my theory that it washed a clump of sludge loose and that started his problem.

 

[Dave]

Sounds like a bad problem. But there must be a whole bunch of early 3.7L KJ's out there with between 50 and 150,000 miles on them so if it was such a common problem (as stated) for the 3.7L it would be all over the website as half the people on this board would be having problems with the early 3.7's and reporting it??? Not to mention that the same motor was used in Dodge p/u's and other vehicles. Seems like something elce is or might be involved as a cause.

Dave

 

[k99jk99j]

Just curious if anyone else is having what I think is piston slap. Since this weekend, it has been getting below 50 degrees at night. When I first start the KJ in the morning, I let it idle for just a minute or two while I wipe the frost/dew off the windows and then drive off. I hear a distinct knocking noise when accelerating that is tied to RPM and load. After just a few minutes of driving, it fades away. I feel pretty certain that this is piston slap. Is anyone else having this? I am still under the 7/70 powertrain warranty and am thinking I may need to take it in to the dealer.

mine has had this noise since the day i bought it new with 12 miles on it! it sounds like a diesel on cold start up. i always thought it was piston slap also. i think it is piston slap be cause the noise is identical to the piston slap noise in my 99 cherokee with a 4.0L. i have heard lots of 4.7L owners reporting the noise also. it seems it does not effect the motor in a bad way. their is no mass reports of 3.7l's blowing up!

 

[k99jk99j]

check this thread out! similiar noise! mike

http://www.jeepforum.com/forum/showthread.php?t=282340&highlight=piston+slap

 

[jg45]

Just to clarify, there is no noise at initial start while it is idling. I can barely perceive the noise if I hit the gas while it is in park and rev the engine a little. It's when I put it in gear and start to accelerate that I hear the noise. I am running 5w30 since the weather cooled down. I have historically run 10w30. That may be why I never heard it before.

 

[sleeve]

My 2002 has nearly 75K miles on it and every winter it makes that piston slap noise. I usually start the jeep about 5 minutes before I leave for work to cut down on the noise. But the colder it gets, the more noises your Jeep will make. You should hear mine in the mornings... The fan makes a horrible noise until the clutch warms up. Top it off with some standard lifter ticking and I have a good old noisy Jeep. To me, it's normal.

If you are worried, take the KJ in and have the dealer or your local mechanic go over everything for you. Maybe there is something wrong. I don't think so, but maybe there is.

As to the problem with the early engines.... Well, I haven't had any problems with sludge or my valve springs. There are a few reports out there about spring failure at 100K miles. But most KJ's do not suffer this problem.

What I do have a problem with is condinsation in the oil fill tube (during the winter only.) I clean that out every 2 weeks with a paper towel to cut down on the water content sitting on my head.

About the oil (from the other board) I've been running Mobil 1 5-30 for the last 6 years (almost 7 years now) and haven't had any issues.

 

[Atrus]

I see everyone talking about 5W-30 and 10w-30...is this what's recommended for older KJ's? My '07 calls for 5W-20. I've run Mobil 1 5W-20 in it since the first oil change at 500 miles, it's now got 26k on it.

 

[sleeve]

Yes, the 2002-2005(?) KJ's were perscribed to run 5w-30. After that, 5w-20 became widely available. Continue to use 5w-20. That is what is recommended for the newer KJ's and all other vehicles practically as well.

 

[Nursecosmo]

Sounds like a bad problem. But there must be a whole bunch of early 3.7L KJ's out there with between 50 and 150,000 miles on them so if it was such a common problem (as stated) for the 3.7L it would be all over the website as half the people on this board would be having problems with the early 3.7's and reporting it??? Not to mention that the same motor was used in Dodge p/u's and other vehicles. Seems like something elce is or might be involved as a cause.

Dave

1 problem here.
http://www.jeepkj.com/forum/showthread.php?t=36110&highlight=valve+problem

9 different people in this thread had the same problem (not all 02 models either)
http://www.jeepkj.com/forum/showthread.php?t=26447&highlight=rocker+fell

2 folks here have it on newer models.
http://www.jeepkj.com/forum/showthread.php?t=29167&highlight=valve+problem

Here is the associated TSB from Chrysler. Sure doesn't sound like a problem to me.
http://home.comcast.net/~merchjo/jee...tsb-page-1.jpg
and
http://home.comcast.net/~merchjo/jee...tsb-page-2.jpg

only 1 here.
http://www.jeepkj.com/forum/showthread.php?t=27143&highlight=valve+problem

2 more cases. Apparently it happens to the #5 valve in the 05 models.
http://www.jeepkj.com/forum/showthread.php?p=266974&highlight=valve+spring#post266974

A couple more listed in this thread from another forum.
http://www.dodgetalk.com/forums/archive/index.php/t-61793.html

Oh look, another one.
http://www.trustmymechanic.com/forum/viewtopic.php?f=1&t=16937&start=0&st=0&sk=t&sd=a

Oh, no. It's not a common problem at all.bs1.gif. These were only the first few listings which I found in a twenty minute search. The vast majority of people with engine problems do not even post anything about them.

jg45; I also found a huge number of references to piston slap with the 3.7.

 

[Marlon_JB2]

But at the same time, you have to remember that people who...

Are Angry: Will express their displeasure with everyone they possibly can.
Are Happy: Keep their mouths shut.

I guarantee there are a heck of a lot more HAPPY people than angry / unhappy people with these 3.7L engines which have a strong reputation for reliability and durability. Mechanics will say anything to make someone feel better or worse. Depends on how their customer takes their comments.

I'm not in denial. I do realize that not everyone will have good luck with the 3.7L engine but I'm just saying, there's a heck of a lot of good 3.7Ls out there than bad ones.

Now if we were talking about the '90s Chrysler 4-Speed Automatics, then I wouldn't be saying anything like that....

Also take into account that there's 2+ Million of these engines out there! A few failures posted on the internet are nothing compared to that huge number.

<-- happy with the 3.7L.

 

[Nursecosmo]

there's a heck of a lot of good 3.7Ls out there than bad ones.

Absolutely no doubt about that. I was simply making the point that it more common than one might think. All automotive manufacturers have quirks with their products. Sometimes the problems just don't start to show up until a few years after production. Chrysler did know about the valve issue, but to fix it would have entailed a pretty expensive redesign of the valve train so they just played the odds knowing that it would cost less to repair the few which showed up with the problem before the warranty expired.