I drive a 99 silverado 1500 z71, she has 197,000 and still running like a champ except for the head gasket that will be replaced soon as i get time. My thing is i bought this truck a year and a half ago with 179,000. I have only heard this knock noise during cooler weather and after a long highway drive(about a hour or longer). I run 10w-30 full synthetic in my truck and noticed that it helped a little but when starting my truck oil pressure jumps to 40 psi and a knocking or "slapping" noise happens for no more than 6 seconds. My biggest fear is that im getting the noises of a soon to be blown motor. I've seen some people say its normal and some people say your a dumb a** if you think it is normal. I would really appreciate to hear what yall have to say about it, whether i need to be pricing a new motor or enjoying my truck. Thanks

 

Enjoy the truck...I've got the same truck. 01 z71 with 198k on the dash and it gives a little piston slap during cold weather. Other than that it still runs just as strong as day one

 

I've had a top end knock on my 2000 Suburban 5.3L since it had 50K on it (intermittent) Think it is lifters. Since you have to replace a head gasket, might be time to look at lifters. I run, and recommend the OEM recommendations on oil, however since I have 170K, I use Castrol GTX extended life at whatever the oil cap says to use, I think 10w-30. Because you are using a full synthetic only means longer oil life, nothing else.

 

Thansk for the replies, I think good idea to look at the lifters. The 5.3 calls for 5w-30 but with all the miles(some are ran hard miles) i run a thicker oil to keep everything lubricated well and not so much now but i live in louisiana and it gets hot as a some b**ch. But thanks again for the info

 

If your not burning oil Id still use what the cap says, I seem to burn a quart every 6 months with 5-30 @ 110,000 so I use a slightly thicker oil full syn to account for that, I change it every 8000 which is about 6 months for me.

 

Always use the proper weight oil. If you use thicker oil yes the oil pressure goes up but the volume of moving oil goes down. At operating temp 5w-30 and 10w-30 is exactly the same. First # 5w or 10w is when oil is cool. The thicker oil takes longer to move through the engine which is worse. I actually put 0w-30 in my truck when I change the oil in the winter time so the engine gets lubrication quicker. If you wanted to run thicker oil you wold need to run ?w-40 or ?w-50, which is still not a good idea. BAck in the older days it was normal to use thicker oils. Now and days engine are built much more percise and oils have come a long way


Oil Additives | MotorWeek

 

I have had my truck for about 7 years now and it has always had a knock even after I replaced the rods and lifters... at first it concerned the hell out of me so that's why I replaced everything but yeah truck has been running amazing even with this coolant issue I posted earlier