Cold engine knock, 3.7L

willness33 · **Joined:** Tue May 16, 2006 3:21 am **Posts:** 7

Ok, I tried the search and got very little. The wife's libby has a pretty bad knock when cold. By cold, I mean it only happens in the winter months and only for about 1-2 minutes after startup. No problems in the warmer months. This isn't typical lifter or valve tick, but a much more ominous, down low knock. It wouldn't entirely suprise me if it were a rod bearing since we've got 156K miles on the thing. What I'm curious of is, does anyone else have this issue? Have you investigated it any? Has anyone tried any oil additives and have they worked? I'm considering some lucas with the next oil change to see if it improves any.

Blue KJ in PA · **Posted:** Tue Dec 09, 2008 9:02 am

willness33 wrote:

Ok, I tried the search and got very little. The wife's libby has a pretty bad knock when cold. By cold, I mean it only happens in the winter months and only for about 1-2 minutes after startup. No problems in the warmer months. This isn't typical lifter or valve tick, but a much more ominous, down low knock. It wouldn't entirely suprise me if it were a rod bearing since we've got 156K miles on the thing. What I'm curious of is, does anyone else have this issue? Have you investigated it any? Has anyone tried any oil additives and have they worked? I'm considering some lucas with the next oil change to see if it improves any.

Cold engine noises are common with the 3.7. My has always made noise when cold until warmed up...using synthetic oil only made a very slight difference if any at all.

TAHOE · **Posted:** Tue Dec 09, 2008 9:50 am

I was wondering that too. My wife's libby sounds like a rod knock for about 1-3 secs on startup. Then my dad's Chevy truck has done it for over 40k and still runs fine, I think his is wrist pin issues.
Couple secs, I wouldn't worry about, but if you have 1-2 mins, sounds like you maybe in for a motor soon. But then whi,le I'm thinking, if it is lasting that long, it should be there all the time. I've had a couple vehicles of late lose a rod bearing, once it's there, it stays. I also had an astro van that sounded like a rod knock, ended up it was the cold fluid in the tranny convertor. It would take 30-40 secs to disappear.

SoDakJeep · **Posted:** Tue Dec 09, 2008 1:32 pm

mine does it quite often in the mornings but as soon as it warms up you cant hear the noise anymore. It only has been happening since its started to get cold 20s degrees. I usally let it warm up for a minute or two before heading out. I hope its nothing serious and I assume it is just because it is so cold out because as soon as it warms up there seems to be no noise.

Jeepjeepster · **Posted:** Tue Dec 09, 2008 1:43 pm

I use 5w-30 in the winter and 10w-30 in the summer. Engine seems to be a lot quieter in the winter with 5w-30..

willness33 · **Joined:** Tue May 16, 2006 3:21 am **Posts:** 7

SoDakJeep wrote:

mine does it quite often in the mornings but as soon as it warms up you cant hear the noise anymore. It only has been happening since its started to get cold 20s degrees. I usally let it warm up for a minute or two before heading out. I hope its nothing serious and I assume it is just because it is so cold out because as soon as it warms up there seems to be no noise.

EXACT same situation as me. What kind of mileage do you have on yours?

willness33 · **Joined:** Tue May 16, 2006 3:21 am **Posts:** 7

Jeepjeepster wrote:

I use 5w-30 in the winter and 10w-30 in the summer. Engine seems to be a lot quieter in the winter with 5w-30..

I'll give that a shot on the next oil change.

mrkake · **Posted:** Tue Dec 09, 2008 4:49 pm

Running a lower weight oil during the colder months will make a difference for you folks up north (assuming that it is just frigid oil that is causing the knock). I have had several vehicles do that when it starts to get cold and that's when I know to swap out for lighter weight oil. It's a good place to start anyway. You have to change your oil eventually anyway and if it doesn't help you will know to look further.

SoDakJeep · **Posted:** Tue Dec 09, 2008 8:16 pm

i know thats the thing tho I have 5-30 amsoil in my jeep. Its only noticeable with the radio off you cant really hear it with the radio on. As soon as it warms up though it seems to be fine and no noises? I will mention that when I head to the dealer tomorrow for an all amsoil stop hahaha. Oil, Filter, F Diff. R Diff and the transfer case.

jg45 · **Posted:** Tue Dec 09, 2008 9:09 pm

Mine is doing it also. I have 65K on it. It is quite until I accelerate, then when I get to about 1500 RPM I hear the knock. On a really cold morning, it sounds like a diesel. I think it is piston slap since it goes away when they engine warms up. It sounds like it is on only one cylinder as well. I took it to the dealer since it is still under the 7/70 warranty, and they said it wasn't loud enough to do anything about.

willness33 · **Joined:** Tue May 16, 2006 3:21 am **Posts:** 7

jg45 wrote:

Mine is doing it also. I have 65K on it. It is quite until I accelerate, then when I get to about 1500 RPM I hear the knock. On a really cold morning, it sounds like a diesel. I think it is piston slap since it goes away when they engine warms up. It sounds like it is on only one cylinder as well. I took it to the dealer since it is still under the 7/70 warranty, and they said it wasn't loud enough to do anything about.

Again, same symptoms. I'm glad I'm not the only one. I'll say one thing though. Aside from a few sets of tires, a few ball joint changes, a condensor and compressor, the libby has been a good vehicle. At 160K miles, I guess I should expect a little engine noise, but the darn thing still runs so well and doesn't burn OR leak any oil. I'll admit that it doesn't get near the wrench time that it deserves and no where near what my TJ gets. I hope it lasts another 100K miles.

sleeve84028 · **Posted:** Thu Dec 11, 2008 5:37 pm

Just wanted to report that my KJ has been making knocking noises since the day I bought it (almost 7 years ago). I've always considered the knock as a "OK, I'm alive" indicator...

Guest · **Posted:** Fri Dec 12, 2008 2:29 am

Jeepjeepster wrote:

I use 5w-30 in the winter and 10w-30 in the summer. Engine seems to be a lot quieter in the winter with 5w-30..

+1
ThunderbirdJunkie also switches up viscosities depending on weather

Prospect62 · **Posted:** Wed Dec 17, 2008 12:55 pm

Mine does it too, when it's cold (below 40F or so) and I start it and go with no warm-up period. I find that letting the engine idle for a couple minutes or so before I start out in the morning eliminates most of the knock. It's a simple viscosity issue. The oil is too cold and thick to lubricate all the parts. Once in a while won't hurt...repeated occurrances might. This is why folks in colder climates should allow a warm-up period on those cold mornings (this is being discussed elsewhere on LOST, or maybe KJ Country) before placing a load on high RPM's on the engine.

I'm considering the switch to 5w-30 for the winter myself.

jg45 · **Posted:** Wed Dec 17, 2008 1:05 pm

The interesting thing is that I did change to 5w30 for the winter for the first time and this is the first time I have heard the knock. Oh well, it sounds like it is a common thing and probably nothing to worry about. Now anyone know how to fix the OPEC problem?

HoppedUpOnGoofballs · **Joined:** Sat Nov 29, 2008 10:36 pm **Posts:** 203

I have a little under 33,000 on my 05, and it has done this for as long as I can remember. I think it also does it when its warm, but cant remember for sure.. But, its only for a few seconds, so I just wait until it stops before I start driving.

I use 5w30 (Mobil1 synthetic) year-round up north here..

tjkj2002 · **Posted:** Wed Dec 17, 2008 11:08 pm

willness33 wrote:

jg45 wrote:

Mine is doing it also. I have 65K on it. It is quite until I accelerate, then when I get to about 1500 RPM I hear the knock. On a really cold morning, it sounds like a diesel. I think it is piston slap since it goes away when they engine warms up. It sounds like it is on only one cylinder as well. I took it to the dealer since it is still under the 7/70 warranty, and they said it wasn't loud enough to do anything about.

Again, same symptoms. I'm glad I'm not the only one. I'll say one thing though. Aside from a few sets of tires, a few ball joint changes, a condensor and compressor, the libby has been a good vehicle. At 160K miles, I guess I should expect a little engine noise, but the darn thing still runs so well and doesn't burn OR leak any oil. I'll admit that it doesn't get near the wrench time that it deserves and no where near what my TJ gets. I hope it lasts another 100K miles.

Well since you have 160k on the ODO I'd check the plastic timing chain tensioners for wear.

DarbyWalters · **Posted:** Thu Dec 18, 2008 9:13 pm

It could be the "wrist pins" are worn and the piston slaps a bit when cold and at low rpms.

dieselenthusiast · **Posted:** Fri Dec 19, 2008 12:37 am

If you're engine is mechanically sound, then you should consider switching to the Amsoil 0W-30. Unless if you have the 07 KJ or 08/09 KK, then you can run the 0W-20. I change my oil once a year. The Amsoil has excellent film strength and saves wear and tear on engines. I've seen Amsoil take gasoline engines to over 350,000 miles. Plus, you’ll save a little mpg.

ShafferNY · **Joined:** Wed Dec 26, 2007 3:51 pm **Posts:** 88

My Liberty has had the same cold engine knock since I bought it a year ago with 74,400kmi on it. It now has 81.000kmi on it. The colder it is out, the more noticable it is.

I always hit the remote starter and by the time I go out, 7-8 minutes later, the temp gage is at 1/4 and the engine knock is hardly noticable.

Even when I can't use my remote starter I always let it run for at lease 3-4 minutes and wait for the temp needle to start to lift of the cold pin.

I always switch to 5w-30 when I do my oil change in the fall.

With the 3.7L's cam design I feel it's always best to give the engine at least 3-4 minutes of run time before going anywhere just to make sure the oil is circulated to the top end of the engine good.

I'm sure some may think that's rediculous, but better safe than sorry.

Cold engine knock, 3.7L

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