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4.0 valve train noise

armadillo66

NAXJA Forum User
With the weather turning cooler, my engine rattled like a Cummins this morning. 98 XJ 4.0 Auto with 115,000mi. No smoke. Just changed oil, 10w30 and I put in a container of STP to see if that had any effect on the noise. Helped a little, noise is less when engine warms up.
not missing any and been getting 16-18mpg adround the city, I do need to put in new plugs and wires when I do my cooling system, belts and hoses next payday.

Anything these engines tend to have go wrong in the valve train I need to know about?

I probably should scout around for a good 4.0 to put away and do a slow rebuild process on for down the road. I got a buddy who runs a remanufacture engine shop in Oklahoma, he said he could get me a decent price on a quality rebuild should I ever need one done.

Being new to this particular engine, I know more about the old 300 inline 6 Ford than I do the Jeep 4.0.
 
Does it respond well to throttle while the engine is still "rattling"?
 
What Oil & Filter did you use?

If I use Dino (ANY DINO including the much vaunted Diesel Rotella) my 140k engine is much noisier than if I use Synthetic, Especially during startup.
I cheaped out & ran Mobil Devlac 15W40 (It was on sale) last month & noticed some not so nice noise @ startup + the Valve train was much louder than normal. I dumped it after 1K miles & put in some Pennzoil Platinum 5W30 I had on hand (My Nissan uses it) & all quieted down + No more loud startup.
I have always run M1 EP, M1 TDT, Pennzoil Platinum Ultra, Rotella synthetic (Whatever is on sale) , with a premium filter (M1, Pure one, Mopar, etc..) With 5-7K oil change intervals & my truck was always very quiet (For a Jeep 4.0!!) .
I try to run lighter weight (Ex. 5W30) in the winter & heavier weight (10-15W 40-50) in the summer)
 
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