Quote:

I am not worried about digging in to it right now, the only time I really notice it is when I start it up early in the morning when it is still cold, it makes some noise and quickly goes away as the oil pressure comes up and is gone when the temp is at up at operating temp.



STLDuster,

Let me see if I understand you correctly. You changed oil grades at approximately 110,000-miles because you started hearing valve train noise? Also from what you’ve stated in this thread, it doesn’t sound like changing to the thicker grade oil took away the noise at cold start-up.

As others have said, it could be loose lash adjusters, or maybe loose lash adjusters due to some valve train wear.

Also, one reason why you could be hearing the valve train noise at cold engine start-up is that the oil is simply too thick. For example, an SAE grade xxW-40 motor oil has a viscosity of around 135 to 165 at the temperature of 104 degrees Fahrenheit (F). But obviously your motor oil temperature is going to be less than 104 degree (F) at cold engine start-up depending on where you live. Although we are not given the viscosity of motor oil at temperatures under 104 degrees (F), we can see from the specs that engine oil thickens as it cools down from operating temperature. By contrast, the same SAE xxW-40 motor oil is rated to have a viscosity of 12.5 to 16.29 at 212 degrees (F). 212 degrees (F) is the motor oil operating temperature, which is not to be misconstrued with engine coolant temperature. At temperatures under 104 degrees (F), your 40 grade oil will be thicker than the above mentioned viscosity of 135 to 165. This can be confusing to some as the SAE numbers on the oil bottle actually represent the grade of the motor oil and not the actual viscosity. A 10W-40 motor oil does not have a viscosity of 40 when your engine is up to operating temperature. This would be incorrect. In reality, SAE specifications state that 10W-40 motor oil has to have a viscosity between 12.5-to-16.26 at the operating temperature of 212 degrees (F) in order to receive the xxW-40 designation.

So this means in the morning when you first start your engine, the oil is excessively thick and does not provide adequate oil flow and protection. When the oil starts to warm up and thin out to its design operating viscosity, you hear the noise effectively go away because the oil started out with a viscosity of 165-plus and then thinned down to the operating viscosity of 12.5-to-16.29. This makes more since when they say 90% of engine wear occurs at start-up.

Your 2001 JEEP GRAND CHEROKEE 4.7L 8-cyl Engine is recommended to use a SAE xxW-30 grade motor oil. The SAE grade xxW-30 motor oils are rated to have a viscosity of around 90 to 110 at 104 degrees (F). To round out the comparison, the same SAE grade xxW-30 has an operating viscosity of 9.3 to 12.49 at 212 degrees (F).

Also, consider that an 0W-30 motor oil will have the best protection at start-up even at 104 degrees (F). 0W grade motor oils are a better choice over 5W and 10W grade motor oils. In fact, some have said that their engine noise at cold start-up was cured by using a good 0W-30 motor oil.

Question: At cold engine start-up, what motor oil viscosity do you want to have flowing through your cold relatively un-lubricated engine?

(A) More than 165
(B) More than 110
(C) Better then the above

If you selected answer (C), take some time and download some Typical Physical Properties data sheets that all the leading motor oil manufactures provide online. By taking some time to study these, you will see that some motor oils provide better cold start protection than others. If you wish, you can start with this Shell Rotella T Typical Physical data sheet pdf file I’ll provide in the attachment at the top of this post.

Compare the ASTM D-445 cSt viscosity @ 40 degree (C), and 100 degree (C).

Note:

40 Degrees (C) = 104 Degrees (F)
100 Degrees (C) = 212 Degrees (F)

Finally, by using an API (SM) rated motor oil, you’ll get less zinc and phosphorous. I’m assuming the 4.7L engine comes equipped with rollorized valve-train like most modern engines. So no need for the higher zinc and phosphorous numbers that can have harmful effects on your catalytic converter.

CompSyn