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low oil pressure, knock, and glitter in oil. 99 5.3

6K views 10 replies 4 participants last post by  99z71silverado53 
#1 ·
Okay guys i noticed yesterday i let my 1999 NBS Silverado 203,xxx miles, warm up in the morning and it was just the normal stupid lifter tick. well 10 min went by went to leave for work and it was knocking. the weird thing is that i can bring it above 1500rpms and it stops then itll come back went it goes under 1500rpms. well i still drove it thinking maybe a CAT blew apart but as i found this morning there is glitter in my oil on the dipstick. but i drove it this morning and once it was operating temp and oil pressure was 25psi at idle the knock went away. i have no loss of power, not a constant knock, i have ruled out the CATS and flexplate considering theres glitter in oil. PLEASE HELP!!!! i work for O''reillys so an oil pump is only $65. i know i need a MAF and Throttle Positioning Sensor when i get payed, so should i go a head and drain the Royal Purple Full Syn out and do a normal oil change with heavier conv oil with additive and see if it changes anything???????
 
#4 ·
Well here's an update. I just checked it all again and it was just the led light on my phone reflecting on the metal dipstick cuz I check the oil and wiped my finger on it and no glitter. And now there's no knock at all. Now I'm just leaning towards carbon build up causing the knock and I drove it hard at operating temp and it may have broke the carbon loose. But oil pressure wise could be cuz I have Royal Purple full syn 10w30 with 3,100 miles on it. So I'll do an oil change and keep you guys updated. I'll still rebuild a 5.3 and do a full LSX build for it in the near future.
 
#5 ·
just drove it to class and oil pressure driving was 40psi idle 20psi. only knock when i bring the rpms to 1500 the let off the throttle. but doesnt knock at idle or when driving that i can hear. big tires make to much noise to hear for engine noises. i maybe thinking a cracked flexplate or bolt or maybe a blown apart CAT now but ill chack it when im home. if all else fails ill dropp $500 on a used engine and rebuilt it with high pressure pump, LS6 cam, Lunati valve springs, and flat top pistons with forged crank. but let me know what you guys think could be the issue.
 
#7 ·
1fast-L76 said:
Again, main or rod bearings. No type of super synthetic motor oil will cure this.
The reason for the knock when you let off the gas is the "unloading" of the bearings.
There is no knock from "engine crud".
Yeap, your not far from complete engine failure. I would be looking for that replacement engine wether used junkyard or good Reman. Tons of decent used 5.3s around, just have to look.
 
#8 ·
If you can't find a 5.3 (I know a good one is a little hard to find by me) a 4.8 should also swap right in. I'd grab the 4.8 computer too though. I know a 5.3 will run fine on a 4.8 computer, but it will be under powered. But I don't know how a 4.8 would react to a 5.3 computer.
 
#10 ·
I don't have a 4.8, I was just thinking that of you can't find a good 5.3 in your area, a 4.8 would work fine too.

By me 5.3's disappear fast and if they are still there, they usually are either shot or have 250,000 miles or more
 
#11 ·
well thanks man but a huge relief off of my shoulders..... i was about to pull the oil pan and beat on the drivers side cat and it raddled. so i started it and put my hand on the cat and i could feel the insides bouncing around so i put my stethoscope to is and reved it and about blew out my ear drums lol. so im having a good friend and muffler shop owner cut off the cats completely. as far as my oil pressure the engine has 203,xxx miles and it also has 3,1xx on full syn oil so its either broken down or the oil pump is weak. but thanks you guys for all the advice and help and ill stay in touch.
 
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