Think what ya want.
If ya had heard more than one that would be different

 

More

I have been building and blowing up engines for 17 years. Rod knock is a common thing. Main knock is not.

Lets think about it logically. Rods move, more or less, up and down. If the bearing is spun, creating excessive clearence, when the rod changes directions you get a knock. However, a crank just spins in place. No lateral or up and down movement (not forces but acutal movement). So if a bearing goes, you loose oil pressues but unless multiple mains go out, no knock.

 

Think what ya want.
If ya had heard more than one that would be different.


Well it seems like I have been doing it for something like 40+ yrs.
Took an early 70's Ford big block for a ride at the Ford dealer I worked at to see what was wrong,It had a knock/noise under the hood.
Couldn't find a noise until with the air on,in gear,holding the brake,and mashed the gas. Guess what it sounded like it was coming out of the frame.
Pulled it out and only the front main was destroyed. This was from air cond. belt being pulled dick ban tight.Probably why they have tensioner now.
If ya haven't run a spun rod brg a bunch of miles it is hard to detect same for a loose brg. Try a poured bearing.
Ya will need to get it to a steady speed and find the sweet spot between pull and decel-- then it will sound off for ya.That is if the rod is not fixing to window the block which is easy.

 

THAT EXPLAINS IT. You are working on a damn Ford!


Agree to disagree.

 

Unless there's existing damage you must ask yourself how water would get past the piston rings into the crank case?


First you say you can hear a "main knock" over a rod knock but then in the above statement you list all kinds of impending circumstances like having to put load on the crank before you heard it. Logic does not explain why you would not hear a component with such reciprocating force like a rod compared to, as PWR SHFT states, a stationary component. You still haven't explained yourself other than establishing your tenure and telling all us kiddies a barstool bed time bull **** story from 1910.

 

No body is talking hearing one over the other.
If ya got a rod and a main knock ya should think about a rebuild.

 

You are stating a rod knock cannot be heard unless it's about to window the block and then go on to say a main "knock" (if you will) can be heard under certain circumstances. I have asked you to explain how that is and you have yet to do so.

 

Rod knock at idle can't be heard UNLESS IT'S FIXING TO COME OUT REAL SOON. A main will knock under a load only. If ya got a stacked main it will flex the crank enough to knock if it has been run any distance.

Best I can explain it.
If it don't meet your standards-- sorry,but I can tell from my description.
Read back on one of my earlier posts and see how I to tell a rod knock before it destroys the engine,HAS NOTHING TO DO WITH IDLE.


Rod knocks are loudest at higher speeds (over 2500 RPM) Feathering the gas pedal may result in a distinctive back rattle between 2500 and 3500 RPMs.
Bad rod knocks may double knock if enough rod bearing material has been worn away allowing the piston to whack the cylinder head in addition to the big end of the connecting rod banging on the crankshaft rod journal. It will sound like a hard metallic knock (rod) with an alternating and somewhat muffled aluminum (piston) klock sound.
Wrist pin knock in modern engines is very rare today but is a favorite for the misdiagnosticians.


Condition Possible Cause Correction
Engine knocks Cold and continues for two to three minutes. Knock increase with torque. a. flywheel contacting splash shield

b. loose or broken balancer or drive pulleys.

c. Excessive piston to bore clearance.

d. bent connecting rod.

e. Piston 180 degrees off
a. reposition splash shield

b. tighten or replace as necessary.

c. replace piston/liner assembly

d. replace bent connecting

e. rotate piston 180 degrees.
Engine has heavy knock, hot with torque applied a. broken balancer or pulley hub

b. loose torque converter bolts

c. accessory belt too tight or nicked

d. exhaust system grounded.

e. flywheel cracked

f. excessive main bearing clearance

g. excessive rod bearing clearance
a. replace parts as necessary.

b. tighten bolts.

c. replace belt or tensioner as necessary

d. reposition as necessary.

e. replace flywheel

f. replace as necessary

g. replace as necessary
Engine has light knock, hot in light load conditions a. detonation or spark knock

b. loose torque converter bolts

c. exhaust leak at manifold

d. excessive rod bearing clearance
a. see detonation diagnosis section 6e

b. tighten bolts

c. tighten bolts

d. replace bearings as necessary
Engine knocks on initial start up but only lasts a few seconds a. improper oil viscosity

b. hydraulic lifter bleed down

c. excessive crankshaft end clearance

d. excessive main bearing clearance
a. install proper oil viscosity

b. clean, test and replace as necessary

c. replace crankshaft thrust bearing

d. replace worn parts.
Engine knocks at idle hot a. loose or worn drive belt

b. compressor or generator bearing.

c. valve train

d. improper oil viscosity

e. excessive piston pin clearance

f. connecting rod alignment

g. insufficient piston to bore or liner clearance

h. loose crankshaft balancer.
a. replace belt or tensioner as necessary.

b. replace as necessary.

c. see valve train noise diagnosis

d. install proper viscosity oil for expected temperature.

e. replace piston liner/assembly

f. check and replace rods as necessary.

g. replace piston/liner assembly

h. torque any or replace worn parts

Detonation/Spark Knock

DEFINITION: A mild to severe knock, that usually occurs under acceleration. The engine produces sharp metallic sounds that change with throttle opening.

*

Check for poor fuel quality, proper octane rating

 

Well you tried and you were successful at making my head hurt. Thanks for your efforts nonetheless.

 

Tell ya what do.

Would you post any test's or documentation you have that is contrary what I have said.


Take two aspirin and call the doctor in the morning.

 

I fell asleep trying to read it. I am impressed you made it through.

 

Okay...
"Rod knock can be heard at points in the rpm range other than revving from 2500-3500rpm."
There. Comparitively speaking that's about as much "documentation" you've supplied thus far. Are you convinced?

 

Tell ya what do.

Would you post any test's or documentation you have that is contrary what I have said.


Take two aspirin and call the doctor in the morning.

 

You already have one individual who has countered your theory with experience yet you try to overshadow his with your six hundred "years of experience."
Doesn't matter what is said.. you won't provide any documentation nor answer any questions, but would rather plagerize some mechanics book on "condition/cause/correction" and dance around the topic.
I know it hurts your feelings, but I believe PWR SHFT over your beginning of time "experience" on this one.

 

That is more documentation than anybody else is providing. Having heard more than one I believe In the way posted to check them.
All ya want to do is bump your gums about what I haven't done or what I don't know.

Suppose you post ANY documentation to the contrary of what I have stated.