Knocking Noise when engine first started up (Please HELP)
 

I have a 98 blazer 98000k on it. Recently i have been hearing a knocking noise from under the blazer when it is started after sitting for a couple of hours. The noise goes away once engine is warmed up. What could this noise be. Can it have anything to do with giving an oil change and putting 5w30 in it. it is about 50 degrees here in Wisconsin. Please Any advise would be great

First off, try changing the oil filter again, you may have installed a defective one when you changed the oil. Watch the oil pressure gauge when the engine first starts... does it take a few seconds to come up? If so then try going back to some 10w30 oil. If that doesn't do it then you may be looking at a new oil pump and possibly more.

Valve noise on start
 

It's possible that this is caused by an anti-drainback valve in your oil filter that is not doing its job. Check out my post here for more details:

https://blazerforum.com/forum/showth...ght=oil+filter


Just changing your oil filter might make this problem go away. Hope this helps!

MrBill99