Since I bought my '01 Suburban 1500 withe the 5.3L engine, I have always heard a knocking sound when first starting up. I reported it back then and was given a letter from GM stating that noise was "normal". Today, 244,000 miles later, that noise has gotten much worse. And it continued to worsen until I found a Bosch oil filter with an anti-backflow check valve in it. If I drive the truck today and start it up tomorrow there will be no knocking. What is "normal" is an avoidable knock in the engine due to oil starvation at start up, a condition that is easily rectified with this Bosch filter. The check valve keeps the oil where it needs to be at start up. If I drive it today and let it sit a few days, however, that oil WILL eventually leak by and the engine will again knock at start up. I wish I had found this out earlier on, but it's never to late to help a great engine hold on longer. I believe AC Delco makes one too, but as far as I know ALL Bosch Steel Tech filters have this feature. They are a little pricier, but well worth the investment to silence this "normal" Chevy engine knock.

 

ru sure its not piston slap. that's what mine had; once the pistons warm up and expand... noise gone

 

I delt with that on my 2000, two pistons were .002 " under clearance.

 

Because changing to an oil filter with a check valve in it seems to reduce that noise I get the impression that this so called normal "piston slap" is GM's way of explaining away a design flaw. Regular maintenance has gotten me to 245,000 miles despite that tho; I just wish I had discovered this filter much earlier...every little bit helps. I remember pulling a cam shaft out of a 327 once; the rear lobes were rounded due to oil starvation at the back of the engine. The cause...who knows? But it proved to me that anything I could do to keep those engine parts properly oiled was worth the effort...although a little pricey, these Bosch filters with the check valves make a difference.

 

have not seen any filters without an antidrain back valve. which ones are you referring to? if they didn't have one; you would hear the knock similar to after a oil change first start up. you would see no oil pressure on the gauge for 2-3 seconds.

 

Bosch Steel Tech has the anti flow check in all filters, I believe. I heard the same about some AC Delco filters too. If others have them as well I wonder why the knocking was so bad before I switched to Bosch. All I know is before I went with the Bosch filter my engine would knock at startup every morning. Since switching to Bosch if I drive it today it will be much quieter when I start it tomorrow. If the engine sits a couple of days however, the oil eventually drains past that check and the engine will be noisy again at startup. O'reilly's Auto Parts list the filter as Bosch 3332. It is a small filter for an engine that size, and Bosch makes a higher capacity one that fits (and I have used) but it is not listed as so. Weird. Also, the only high mileage oil i could find in the 5 qt bottles of 5W30 was a synthetic blend; the only way to buy regular high mileage oil is by the quart. If I'm not mistaken the engine used to be quieter upon startup on any day following one where the engine ran back when standard high mileage oil was used. Is the synthetic blend slipping past the check valve more easily? I don't know, but like I said anything that helps me squeeze more miles out of what is my last Suburban I am all for it. Now I'm tempted to buy standard high mileage 5W30 by the quarts and see if it makes a difference. Like a bumper sticker on an old rusted out chevy with more fender gone than remained read, "A man and his truck...it's a beautiful thing."