I have a 2000 Blazer with a 4.3 it has 82000 miles on it, the last couple of times when I change the oil and filter it rattles for a few seconds when I start it then goes away. Now it is making the noise every time I start it and you can hear the rattle under normal take off then goes away or gets quiter when it shifts to 2nd. I am runing 5w30 oil with ac delco oil filter. The oil pressure guage reads only 20-25 at 2000 RPM and about 10-12 at idle @650 RPM. Any ideas?

Thanks Jerry.

 

That still is in the safe range, but hook a mechanical oil pressure gauage to the sender connection and see what it says.

 

Thanks, but still trying to under stand the rattle when it is started, and is worse after the oil change. I have checked the bolts on the flywheel and thay was tight. Could it be the main bearings or something leaking off or can that happen?

Thanks Jerry

 

try running a thicker oil 10w-30 see if that helps

 

I think you have the FAMOUS Blazer engine rattle. I have the same. I keep being told it is piston slap. I was reading a TBS about a chain tensioner which is new to me. I didn't know a 4.3 V6 had a tensioner. I'm not aware of another engine option in 1997-2000 S-10 Blazer's I thought the 4.3 was it.
Anyway ours has been rattling for 33,000 miles & still is the same as when it started. I run NAPA synthetic 20-50 oil, but even with 10-30 it runs 20 PSI @ idle & 40-45 with RPMs.
So I say drive it, keep tow insurance. Have fun. That is what we do.

 

It could be the regular 4.3 knock,btw they dont have a tensioner from the factory only the late models did,others are suppose to be added to eliminate the noise. The oil pressures are above the gm specs but not by much, they seem low compared to the average pressures on an engine running 5w30. On synthetic hot I get 20-25 at 550rpm and 60 at rpm.

 

What is the REGULAR 4.3 KNOCK? What years did they use tensioners? Where they 4.3 V-6?
Thanks

 

Personally sounds like its a lifter tap which is notorious in Blazers. I get it every once in a while when i start up. Its from the oil draining out of the lifters and when you start up it pressurizes the lifters again and gets them all pumped up and the noise quits. that would explain it when you change the oil and it takes a sec for all the oil to get everywhere again. Just a thought.


Matt

 

Well personally..sounds like you need some thicker oil..i would recommend 10w40- 20w-50 oil. Also if the sound sounds like a hollow knock then it could be worn bearings . if its a higher pitched tapping knock ..then as said it could be just a lifter or two collapsed or sticking.
If you are pondering changing the oil for the thicker stuff then i would run some sea foam in it for a lil bit before the oil change. If it is a lifter problem it could fix it.
Also...that sounds like some low oil pressure to me. best of luck

 

sounds like sticky lifters.