Knocking POS engine.

:swear::swear::swear::swear::swear::swear::swear:: swear::swear::swear::swear::swear::swear::swear:


I just finished spending about $2grand on repairs/mods to my truck and today I heard an oh so sweet knocking noise come from the engine. Needless to say, this caused me to come up with many new swear words. I have read some threads and will be flushing out the oil, this week.
I just wanted to ask if the oil flush doesn't help....What else can i do that wont bust the bank???

Might not stop the knock but you can try Mobil1 5W-30. FOllow the flush directions as you have read in these posts, idle for 45 minutes then drain. Do not rev or race the engine. Stay away from Fram filters as everyone would say and buy a stant radiator cap. What was done in the shop to your truck?

Or should I say what did you do that cost 2 grand and was it knocking before? Or a slight knock?

no knock at all before, it started today?
$2 grand in Headgasket, headers, fuel pump, had the bumper/grill painted to match the body, new hub and wheel bearing, starter.

Just wanted to show you guys the diffrence it made in the look.
Before::
http://files.automotiveforums.com/gallery/watermark.php?file=/503/302694PICT0029-med.jpg

After::
http://files.automotiveforums.com/gallery/watermark.php?file=/500/302694blazer_front_2.jpg

What oil and filter are you using?

How is the oil pressure?

ac delco filter...
when I start up it runs normal, but after about 5min my oil pressure drops near zero.
As soon as I step on the gas it goes back up. Its kinda hard to tell because the oil pressure gauge is crap it has markers at 0,275,500

So if you raise the rpms, the knocking goes away?

When was engine work done to it, how long ago? Does oil pressure come back up right away to normal as soon as you step on the gas? Something might have gotten stuck somewhere causing either a restriction, or maybe the oil pressure bleed off valve on the oil pump can be stuck open exhausting to much oil at idle. Sounds possible since something like a piece of gasket material or debreis can easily get into the engine when the head gasket was done.

So if you raise the rpms, the knocking goes away?
no, it gets louder and faster as the rpms go up!

When was engine work done to it, how long ago? Does oil pressure come back up right away to normal as soon as you step on the gas? Something might have gotten stuck somewhere causing either a restriction, or maybe the oil pressure bleed off valve on the oil pump can be stuck open exhausting to much oil at idle. Sounds possible since something like a piece of gasket material or debreis can easily get into the engine when the head gasket was done.
The repairs were done 2-3 weeks ago, I haven't heard or had any problems with it till today! I can honestly say it ran perfect before the noise started. The oil pressure does go up as soon as i step on the gas.

Thanks for your help in advance!!

Sounds like the crank is letting go.

Sounds like the crank is letting go.

Thats what one of my friends said aswell. I'm going to the shop tommorow. I just hope it doesn't kill my wallet to get this fixed.

thanks for the advice BLT.

You will practically have to rebuild it.

I would have a look at the local boneyard for a cheaper replacement.

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

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.

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.

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.

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.

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.

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.

thanks for all the advice guys!

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.

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

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.

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.

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.

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??

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.

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!!

Not a quick fix...a Cause!!

Honestly, do you REALLY think upgrading an exhaust can throw a crank bearing?

I don't think so. If that was so, we would see knocking hotrods and sports cars dying all over the road.

In response to BlazerLT: a 94 blazer is FAR from a sports car, everything on there was designed with a specific purpose in mind. Where as a sports car's main goal is performance.. not economy, ease of manufacturing, etc....


I would have to chalk this up to a classic case of "if it ain't broke don't fix it"
I had an 87 chevy caprice with the 4.3 in it, ran with a knock in it since the day I got it, drive over 100,000 miles, 2 tranny rebuilds later I sold the car as is for a few hundred dollars.

The moral to the story...either fix it.... deal with it ..... or sell it and move on to a whole NEW set of problems.

I would have to chalk this up to a classic case of "if it ain't broke don't fix it" one of life's hard learned lessons but some lessons are learned the hardest ways.

:2cents:

In response to BlazerLT: a 94 blazer is FAR from a sports car, everything on there was designed with a specific purpose in mind. Where as a sports car's main goal is performance.. not economy, ease of manufacturing, etc....


I would have to chalk this up to a classic case of "if it ain't broke don't fix it"
I had an 87 chevy caprice with the 4.3 in it, ran with a knock in it since the day I got it, drive over 100,000 miles, 2 tranny rebuilds later I sold the car as is for a few hundred dollars.

The moral to the story...either fix it.... deal with it ..... or sell it and move on to a whole NEW set of problems.

I would have to chalk this up to a classic case of "if it ain't broke don't fix it" one of life's hard learned lessons but some lessons are learned the hardest ways.

:2cents:

Your opinion is noted but the last time I checked, the engine in a sports car ran off gasoline and had an exhaust as any other.

Just because it is bolted into a sports chassis makes no difference.

Upgrading your exhaust will NOT cause your engine to knock.

In response to BlazerLT: a 94 blazer is FAR from a sports car, everything on there was designed with a specific purpose in mind. Where as a sports car's main goal is performance.. not economy, ease of manufacturing, etc....


I would have to chalk this up to a classic case of "if it ain't broke don't fix it"
I had an 87 chevy caprice with the 4.3 in it, ran with a knock in it since the day I got it, drive over 100,000 miles, 2 tranny rebuilds later I sold the car as is for a few hundred dollars.

The moral to the story...either fix it.... deal with it ..... or sell it and move on to a whole NEW set of problems.

I would have to chalk this up to a classic case of "if it ain't broke don't fix it" one of life's hard learned lessons but some lessons are learned the hardest ways.

:2cents:

Your opinion is noted but the last time I checked, the engine in a sports car ran off gasoline and had an exhaust as any other.

Just because it is bolted into a sports chassis makes no difference.

Upgrading your exhaust will NOT cause your engine to knock.