Knocking noise

-
340luckyman

340luckyman

FABO Gold Member
FABO Gold Member
Joined
Apr 23, 2014
Messages
52
Reaction score
21
Location
Maryland
i have a 340 small block and today it started making a knocking noise. Would a water pump make a knocking noise? I took the belt of and the noise seems to go away. The water pump seems to spin pretty freely.
 
Flex plate bolts tight? Lifter tick? You didn't tell us where the general area is. It could be the neighbors bangin' for all we know.

Gotta isolate that stuff man, a broom handle or a mechanics stethoscope are your friend.
 
Could be the neighbors lol. I checked the flex plate bolts they are tight. Noise is coming from front of the motor. I tried a long trans funnel but couldn't hear much. Put the belt on and off twice and the noise does seem to go away with it off. The noise also seemed a little louder under the front of the motor but wasn't present with belt off.
 
There was a guy on here that had cooling problems, and it ended up that the rotor blades were slipping on the shaft and not able to push the water through enough. Take the water pump off and see if the rotor blades can turn on the shaft or not... the rotor may be loose to the shaft...

Just another possibility...
 
had the same problem on a big block harmonic balancer was bad put a new one on and noise went away one way to tell if it's bad is that when you try to time it the mark jumps all over the place
 
I had a balancer that cracked at the keyway one time and you could twist it back and forth.
 
I have a 340 and the harmonic balancer bolt cam loose and would make a knocking noise took belt off and noise would change. I took bolt out and put thread lock tight on it and noise was gone. might want to check that also..
 
As others have already mentioned, Id check the balancer. I bought a nice running 70 340 for dirt cheap a few yrs back. Guy thought it was knocking and so it sounded. After further investigation the keyway groove was worn and balancer slid on and off pretty loosely. New balancer and im still running it to this day.
 
You may also check the crank pulley itself for being cracked near the bolt holes and the water pump pulley. They will make the sound you are talking about. Over tightening of the belt can cause these to fail and crack. Ford had an issue with this a lot.
 
timing chains are known to slap the timing case as well......

I thought I had a KNocker one time

I tore the engine down to find the OIL SLINGER installed backwards....less than 5,000 miles on a "Fresh" engine.
 
To answer the actual question, Yes.
A water pump can make a knocking sound, as can the belt fitting too deep into the pully.
To easily diagnose a belt noise, take a bar of soap and touch it to each side of the belt with the car running.
The sound will go away instantly if it is indeed the belt/pully making the noise.
You would be surprised what kinds of noises rubber and steel rubbing together can make.
 
I think I found the problem. The crank pulley was loose and with the belt on it just made it louder. Thanks for everyone's input!
 
You must log in or register to reply here.
-

Back
Top