Rod knock?

[Kingfish]

My wife's 03 has what sounds like a slight rod knock when cold, but when the engine warms up the noise goes away. Oil level is normal. Is it possible this is a valvetrain noise? Can't figure out why it'd be temp dependent though.

 

[LibertyTC]

Are you running synthetic or dino in hopefully 5W-30?
Are we talking freezing temps parked outside?
How many miles on this 3.7 engine?

 

[Kingfish]

10W-30 dino, and it's got 110k. In CT so the sub-freezing temps haven't happened yet.

 

[LibertyTC]

Why 10w-30?
5W-30 is preferred and mentioned on cap.
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I would recommend a good synthetic like Penzoil Platinum in 5W-30 and see if that helps the objectionable noise!

 

[tommudd]

All depends on how it has been taken care of. I've heard them sound like they are on their death bed at 75,000 but others well maintained sound great at 250,000

 

[Kingfish]

IBD. The last oil change was done by a garage and I just assumed they used 10 weight. It's due for its next change, so will look into a full syn 5W-30. But what about the syn oil might make a difference in the noise?

 

[tommudd]

IBD. The last oil change was done by a garage and I just assumed they used 10 weight. It's due for its next change, so will look into a full syn 5W-30. But what about the syn oil might make a difference in the noise?

If it has an internal issue, no matter what you run its going to make noise.

 

[Kingfish]

If it has an internal issue, no matter what you run its going to make noise.

Sure, but why does the tap go away when the engine's warmed up?

 

[LibertyTC]

Tolerance issue when cold? Once things expand/warm up, a sticky lifter may free itself for instance.
Frequent maintenance every 3500miles/ oil & filter changes using Synthetic 5W-30 should be tried & see what happens.
If you did have 10w-30 in crankcase that is not going to help at all.

 

[kejobe]

A year or so ago I needed an oil change. Didn't have the money at the time for Mobil 1 so I did the Autozone special. It was the STP dino oil (5w-30) and STP filter. Every time I stared the Jeep it would knock for a few seconds and the oil light would come on. If I shut it off and restarted the light would go out.

The STP wouldn't flow quick enough to protect the motor. The colder outside temp, the worse it would be.

About 2 weeks later I bit the bullet and got Mobil 1 5w-30 and a Mopar filter. It's been fine ever since using these.

Point of story is the brand and type of oil, along with the weight can have a significant impact on how a motor runs and reacts.

I'd start with a good synthetic oil and a good filter and go from there.

 

[HoosierJeeper]

Guessing that was a ADBV issue in the filter. Mopar filters are OK, but made my Purolator so I won't use them, they've been having tearing issues lately.

My KJ always rattled for a second upon startup ever since I got it back in 07...always used Puro filters. Joined Bob is the Oil guy forums and saw that Fram had done a whole turnaround and is considered good by them, tried a Tough Guard and the rattle went away. Wix is good too, but owned by Mann-Hummel like Puro so I'm not sure if they've had the same cost cutting.

 

[Kingfish]

Why 10w-30?
5W-30 is preferred and mentioned on cap.
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I would recommend a good synthetic like Penzoil Platinum in 5W-30 and see if that helps the objectionable noise!

My wife's car doesn't have that cap. Anyway, an update...
The issue was a vacuum hose (pcv?) and the noise was from a lifter (or two). Once that was replaced the top-end noise went away.