I have a 98 Blazer with the 4.3 v6 and it started knocking on my way home. It sounds like a rod bearing but im not sure. It has 150,000 miles on it, I change the oil regularly,and do regular maintenance. Im not sure if i should spend the money on my old engine or buy a rebult one. It is a heavy knock. Has anyone had a problem like this?

 

You do have oil in it right?
What kind of oil pressure does it have?
Did this start out of the blue or were you running the heck outta it?
Does it knock less at a higher rpm?

 

It has the correct amount of oil, and it has never run low. I have never overheated it either. I was driving at 70 mph and it knocks all the time. It is louder at higher rpm, and when i let off the throttle it kinda rattles. The oil pressure changes with rpm a lot. I do not remember it doing it that bad. driving its about 40 and idle its about 25 or
30.

 

If you have good oil pressure then you may not have an engine bearing problem. Are you sure it's not a lifter? Maybe something else all together like a torque converter?

 

Hi!
Did you tried to check where is it coming from?
Do you hear it in the middle of the engine?
Do you hear it more from the bottom of the car?
In my car it's finished by engine rebuilt :-(

 

My blazer is doing the same thing yours is but mine isn't on the road but when its running my engine is knocking and when i rev it the knocking gets louder as the rpm's go up but goes back to the way it was when the rpm's go down. but my oil pressure at idle is around 40 and goes up to about 50 when i rev it. so idk

 

I just picked up a 99 blazer for $500 that has a bad motor... bad knock in the bottom end that I'm pretty sure is a broken rod... but its obviously bad... like its scary to idle... I certainly would never drive it... so if u r driving it and it doesn't sound like something his.slamming your truck with a sledgehammer then I'm thinking u might wanna look for another cause... lifter or valve sounds more like it

 

Just wondering why you asked if the engine knocks less at higher rpm? I have a 2000 blazer and just did a head gasket/head replacement. The engine wasn't knocking at all before the repair and now after fixing it it runs perfectly.
However when its first started cold no problems but after it warms up it starts knocking at idle and off idle. It seems that it goes away or gets quieter at higher rpm or under load like brake torquing it. I'm wondering if it spun a bearing after replacing the heads? Maybe some water got in the oil after the head replacement and caused bearing failure? I'm thinking of trying to pull the oil pan and replace all the bearings as the knock is new and it may not have hurt the crank yet. Dunno if it will work but it might be worth a try.