Knocking POS engine.

[BlazerLT]

Originally Posted by blazes9395

What makes you think its the crank? He stated the truck was working fine until now.

Knocking plus lack of oil pressure usually means one of the crank bearings has let go.

[herkyhawki]

If you short-out or disconnect one plug wire at a time, the knock may get louder or softer. This wil help prove bad rod bearings. It's probably not worth arguing "is it a main or a rod bearing" as the engine will have to come out to fix either.
Before you decide to pull the engine, remove the serpentine belt and start engine for a short time - to make sure that you are not getting some strange sound from accesories like AC, pwr Steer, alt, Wtr pump.

[scholzee]

Knocking is never caused by a main bearing. Only connecting rod bearings can knock because of the verticle motion as the piston goes up and down and combustion pressure. A main bearing never moves off its center of rotation, no verticle motion, no knock. Low oil pressure can be bad or plugged oil pump, plugged return passages, worn cam bearings, worn connecting rod bearings, or worn main bearings.

[Sen Sen]

my mechanic said it's most likely the oil pump dying and if it's anything more than that, Im replacing the damn engine. Im so sick of shit breaking down.

[JA no Y]

Originally Posted by Sen Sen

my mechanic said it's most likely the oil pump dying and if it's anything more than that, Im replacing the damn engine. Im so sick of shit breaking down.

I have an "88 Blazer that I had to replace the engine in it (because I found a newly rebuilt engine for the price it would have cost me to rebuild) because the engine was knocking SEVERLY. I mean so severly that it sounded like a Harly Davidson going down the road. When I took it out and pulled the oil pan off, I had 2 baerings that were worn out. One was so severe and had so much "play" in it, I first thought the bearing was gone.

I have replaced bearings on the crank b4 in older engines but this one was too scared to do anything with.

[blazes9395]

Originally Posted by scholzee

Knocking is never caused by a main bearing. Only connecting rod bearings can knock because of the verticle motion as the piston goes up and down and combustion pressure. A main bearing never moves off its center of rotation, no verticle motion, no knock. Low oil pressure can be bad or plugged oil pump, plugged return passages, worn cam bearings, worn connecting rod bearings, or worn main bearings.

I agree, but the way mains knock is because of the excessive tolerence)if they are worn) the upward and downward motion will pull and push the crank and cause noise...since work was done 2-3 weeks ago, very good likely hood something got in there and is casuing your problem.

[Sen Sen]

thanks for all the advice guys!

[biv343]

Cam bearings going south are a pretty common cause of low oil pressure. I'll agree with the consensus that the knock is a rod bearing dying a slow death.

[biv343]

Gotta learn to read - scholzee already mentioned the cam bearings.

[BlazerLT]

Originally Posted by biv343

Gotta learn to read - scholzee already mentioned the cam bearings.

More than likely it is the crank bearings causing the knock and the low oil pressure than the cam.

[Rmbodie]

sometimes the bearings on the crank shaft get starved for oil when engine work is done and the distributer is reinstalled without priming the pump. It may have just been its time. Maybe you can use a large wrench and socket to hand turn the engine thru a revolution and stop and turn the opposite direction every now and then to see if you can feel the slop in the bearing to confirm it. Hate to think you may have wasted the money on the engine work though.

[tom3]

Knocking and low oil pressure sure point to the crank I'd think. Spun bearing would be my guess but without hearing the knock it's hard to say. Don't think 5w30 oil will work either. Might try some 15w40 Rotella T as a last ditch effort to run it a bit longer.

[Sen Sen]

I was just going through some past post and another member said that if you don't have proper backflow from "cutting out a muffler", it could lead to engine knocking???
I've done a performance exhast on my blazer a year or two back.
It's 3in pipe with a magnaflow muffler, I had the cat converter cut out.
Would this be a cause to my problems as well??

[BlazerLT]

No, you need to stop looking for a quick fix for this and realise that there is only one way to fix a knocking engine.

You don't see all the sports cars developing knocking engines when they upgrade their exhaust.

[Sen Sen]

Originally Posted by BlazerLT

No, you need to stop looking for a quick fix for this and realise that there is only one way to fix a knocking engine.
.

Not a quick fix...a Cause!!