Jeep 232, 258 and 2.5L AMC Inline Six-Cylinder and 2.5L Valvetrain Noise and Valve Adjustment

[Mike]

Good info, thanks.  Here's an odd one I have been trying to figure out for years.  I bought the Jeep at 57,000 miles ('97 TJ w/ a 2.5L), and now it has about 200,000.  So I am assuming now it's worn out and am just going to swap it out.  But, this is what it has done for years:

 

First cold start of the day, it is quiet.  After about 30 seconds or a minute of warming up, I can hear a valve clatter/tapping noise starting.  It did this until the engine was up to temp, then would go away as long as the engine stayed running.  If it sat for a while and cooled off, it would do it again until warmed up.  This never impacted the engine's performance or drive ability, so I never really worried about it.  

 

But, in the last year of driving it, the noise would appear at about 30 seconds or 1 minute of run time, but would stay once the engine warmed up.  It would be quieter once warm, but definitely audible.  It almost sounds like a diesel.  

 

This Jeep has sat now for about a year and a half, but I am going to revive it this winter, as well as do another build on it.  Also plan to swap the engine for something else, but will always be curious as to what was making this noise.  When I have a chance, I am going to tear the engine down and see if that shows anything.  

 

It definitely doesn't sound like a rod knock, and is coming from the upper part of the engine.  So I am assuming it is something in the valvetrain.