dave1123

What is it that makes all the noise in the AMC 4.0 I6? I know it's not a problem because they all make noise, but it seems to be just at or near idle. I had one guy say it's because the lifters don't get enough oil to stay pumped up but I question that. I know lots of people don't like them because of the noise, they question the engine's condition, but we who know them love them because they seem to last forever.

What is really going on inside?

sthon

inline engines have a lot more lifter noise than a v engine because of the location of the lifters. The 4.0 has also been known to have some piston slap until it it gets up to temp.

dave1123

Ordinarily, I'd agree with you on that, but my 00 WJ doesn't make a lot of noise and it's got 129K on it. Maybe Jeep changed the lifter design in later years. I don't remember the old Chevy "Blue Flame" 6's rattling at idle like that. Of course, I'm getting on in years so maybe I don't remember. My wife keeps telling me that!

I may not remember but I never forget!

sthon

By design the lifters are closer to the outside of the block on an inline engine. Less metal between them and the outside of the block = more noise. This isn't to say the noise is normal, just that you will hear lifter noise much more prominently on an inline engine.

pwb

maybe time to replace the lifters?

baseman

or increase the viscosity of the oil or add an additive???

dave1123

Guys! I'm talking about a NORMAL engine in good condition! This noise is inherent with this motor and is nothing that needs fixing. I was just curious as to what parts are creating the noise, that's all. My 97 ZJ has 208K in her and 40 psi oil pressure at idle hot, doesn't use or leak any oil, and pulls like a mule. (That is, slow off the mark, but strong and steady.)

I don't have a problem with that!