knocking sound
Thread Starter
Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
knocking sound
Ok, I know engine noises are extremely difficult to diagnose over the internet, but here goes.
I had an exhaust leak that was making a high pitched, ticking sound. Replaced exhaust manifold gaskets and that noise is gone.
Now I’m hearing a lower pitched knock sound. It’s almost a hollow sound like tapping on a coconut with a hammer. Sometimes it is just barely audible at idle, some times not. It is not audible until the engine has warmed up. It is most audible between 1000 and 2000 rpm. It seems to disappear above that.
I’ve readjusted the valve lash per the FSM. Timing is at 8* at idle with vac can disconnected.
Motor is not original. It was built up and installed in the car about 7 years ago. In that time I believe I’ve only put about 6 to 8 thousand miles on it.
I’ve not checked compression yet, but I’m getting 21" of vacuum at idle and the needle only fluctuates about 1/4" so I don't think the compression can be too terrible bad.
Anybody have any thoughts? Need more information?
Any chance that this sounds like something I can repair with out removing the motor? I don't have a hoist or a stand at the moment.
Any help is appreciated.
thanks,
Mike.
I had an exhaust leak that was making a high pitched, ticking sound. Replaced exhaust manifold gaskets and that noise is gone.
Now I’m hearing a lower pitched knock sound. It’s almost a hollow sound like tapping on a coconut with a hammer. Sometimes it is just barely audible at idle, some times not. It is not audible until the engine has warmed up. It is most audible between 1000 and 2000 rpm. It seems to disappear above that.
I’ve readjusted the valve lash per the FSM. Timing is at 8* at idle with vac can disconnected.
Motor is not original. It was built up and installed in the car about 7 years ago. In that time I believe I’ve only put about 6 to 8 thousand miles on it.
I’ve not checked compression yet, but I’m getting 21" of vacuum at idle and the needle only fluctuates about 1/4" so I don't think the compression can be too terrible bad.
Anybody have any thoughts? Need more information?
Any chance that this sounds like something I can repair with out removing the motor? I don't have a hoist or a stand at the moment.
Any help is appreciated.
thanks,
Mike.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
That kind of knocking is usually a rod bearing with too much clearance. When cold it's still tight around the crank but when it warms up the oil thins and the metal expands and it starts knocking.
I don't recall a rod bearing knock going away at or above 2K RPMs, so that might point to something else.
Bad news, IF it's a rod bearing, the engine has to come out, the heads need to be removed, all rods need to be checked and repaired, and the crank needs to be replaced, and generally, along with the rod that was knocking.
Not a weekend task unless you have the proper tools.
Lets home someone else comes up with something other than a bad rod bearing.
I don't recall a rod bearing knock going away at or above 2K RPMs, so that might point to something else.
Bad news, IF it's a rod bearing, the engine has to come out, the heads need to be removed, all rods need to be checked and repaired, and the crank needs to be replaced, and generally, along with the rod that was knocking.
Not a weekend task unless you have the proper tools.
Lets home someone else comes up with something other than a bad rod bearing.
Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Take a wood dowel or long rubber hose and listen to your valve covers over each plug....Idea here is to isolate on noise source....if nothing there,listen at oil pan..or low on block.....(block wheels,etc..)
Let us know what you find..
Good luck...
Let us know what you find..
Good luck...
Thread Starter
Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
I've been poking around my engine with a piece of tube in my ear trying to find the source of my knocking.
it gets distinctly louder at the upper right hand corner of the timing chain cover and becomes less if i move away from that point in any direction.
it's less hollow than i had said it was in my original post. i was going off of memory when i typed that. more of a "clack" sound.
i still think i should poke around down by the oil pan and lower on the block just to be sure that there is no knocking comming from that area either.
does this give anybody any ideas of what it mite be? timing chain hitting the cover maybe?
it gets distinctly louder at the upper right hand corner of the timing chain cover and becomes less if i move away from that point in any direction.
it's less hollow than i had said it was in my original post. i was going off of memory when i typed that. more of a "clack" sound.
i still think i should poke around down by the oil pan and lower on the block just to be sure that there is no knocking comming from that area either.
does this give anybody any ideas of what it mite be? timing chain hitting the cover maybe?
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I'm wondering if you might have one of those crappy plastic covered timing gear sets. The plastic breaks off and leaves you with a mess.
Could also be the fuel pump actuator arm on the cam making the noise.
Thread Starter
Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
i suppose i could pull the cover off and have a look. that looks like something i can do with out having to remove that f-ing fan schroud.
i don't remember hearing the noise when i put the tube down on the fuel pump. the pump is kind of oily if that matters. i'll check the pump better when i poke around down by the pan. the pump should be a little easier to get to from down there.
i'm pretty sure it is not the water pump. all i hear from that is a steady "whirr" sound.
is it that they cote the teeth in plastic to cut down on noise or something? sounds like a bad idea to me.
my timing holds pretty steady where ever i put it. currently i set it to the factory setting of 8* just to rule out detonation. i also only feed her premium gas.
i appreciate the help and ideas, Durango boy.
thanks,
Mike.
i don't remember hearing the noise when i put the tube down on the fuel pump. the pump is kind of oily if that matters. i'll check the pump better when i poke around down by the pan. the pump should be a little easier to get to from down there.
i'm pretty sure it is not the water pump. all i hear from that is a steady "whirr" sound.
is it that they cote the teeth in plastic to cut down on noise or something? sounds like a bad idea to me.
my timing holds pretty steady where ever i put it. currently i set it to the factory setting of 8* just to rule out detonation. i also only feed her premium gas.
i appreciate the help and ideas, Durango boy.
thanks,
Mike.
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Thread Starter
Racer
Joined: Mar 2005
Posts: 487
Likes: 0
From: Jacksonville FL
i'm sure that rod isn't all that expensive. maybe i'll try that route.
did your buddies old push rod look obviously damaged?
Racer
Joined: Jun 2007
Posts: 291
Likes: 6
From: Delray Beach FL
Pull the fuel pump from the motor and start the car. It will run for about 30 seconds with the gas in the carb and see if the noise goes away. Remember to put a rag below because some oil may come out from pump open in the block. I was hoping my problem was a fuel pump turned out be number one rod bearing spun.
Marty
Marty
