The 5.3 Liter in my '01 Chevy has had a knocking noise at startup since I bought it new. That noise continued to get worse, and despite a letter from GM stating that this noise was normal, I looked for a solution. What I found was a Bosch filter with a check valve which helps keep the oil in the engine after it is turned off. If I run that engine today, there is virtually no knock tomorrow when I start it up. However, if I run that engine today and let it sit for a day or more, that knock returns as the check valve does eventually let that oil slip past it and back into the pan. With 235K on this original engine, this filter helps keep it going; and with the price of new vehicles, that's a big plus. I understand that AC akes a filter with a check as well, although I have not tried it.
Engine knock at start up
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With 235k miles on the original engine with this "knock" from new, I don't understand the concern. If is truly a knock, it would not be related to the oil supply, but pre-detonation. What grade fuel are you using? Have you checked/cleaned/replaced the knock sensors? Most vehicles with knock sensors will knock momentarily at start-up because the sensor does not yet have a signal to respond to. But, with 235k miles, I don't understand the concern.
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Are you sure it's a knock and not a tick. A knock is more like a hitting a 2 x 4 with a rubber mallet unless like stated above it's a detonation knock or ping. A knock usually indicates a crank shaft going bad and that wouldn't last 235k like that either. If it's just on cold startup I would guess it's a lifter tick.
Either way 235k tells you that everything is okay if it has done this from the very beginning. Some motors just make more noise than others at times.
Either way 235k tells you that everything is okay if it has done this from the very beginning. Some motors just make more noise than others at times.
It's an oil supply issue; that's why using the Bosch filter with the check valve keeps the oil up in the engine where it is needed at startup and hence the lack of engine knock on any day following a day where the engine had run. Piston slap, aged engine, call it what you want, the proof is in the pudding as my old engineer teacher used to say; the knock of an oil-starved engine at startup is easily resolved with the proper filter. Try it, you'll see the difference. Others that I have told about this remedy were glad that they did.
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