Uh oh! Engine knocking?

[Bryan]

hey guys, I have a 8v71 engine. Today, it started making a loud knocking sound. Basically, when we start it, after about 3 to 5 seconds of idling, it starts knocking. Here is what we know, the water lines and heater lines are warm (not hot, not cold), and the oil pressure is at about 12lbs. What could this be?

[luvrbus]

12 lbs at what rpm,any white smoke ?

[Bryan]

12 lbs at what rpm,any white smoke ?

basic idle so aprox 1,000 rpms, we haven't started it in about a month or 2, so there was some white smoke at the very beginning, but seemed to go away

[luvrbus]

If it was only 12 lbs at 600 rpm which is the idle speed without the fast idle engaged on a cold engine you do have a problem any idea what the engine temp was ? 12 lbs is not bad for a hot engine at idle

[grantgoold]

Have you gone back to the engine compartment and tried to take a video? This might help the experts on this board, watch the video and could perhaps be more specific in their help! 

Grant

[Bryan]

If it was only 12 lbs at 600 rpm which is the idle speed without the fast idle engaged on a cold engine you do have a problem any idea what the engine temp was ? 12 lbs is not bad for a hot engine at idle

I'm not sure what is considered a hot or cold engine. We had it running for about 10 minutes and then cut it off, Then we started it again to move it, it was during this time that the sound started.

[Bryan]

Have you gone back to the engine compartment and tried to take a video? This might help the experts on this board, watch the video and could perhaps be more specific in their help! 

Grant

great idea! working on the video right now, will post it in 5 minutes.

[Ace]

Sounds like a bad air compressor


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[Len Silva]

Is it a stick?  I had broken flywheel bolts sound just like an engine knock..

[Bryan]

here is a video!

http://youtu.be/q1CyitEufWU

[luvrbus]

Sounds more like a clutch to me try depressing the clutch and see if it goes away

[Ace]

Sounds louder on the fan side than on the clutch side


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[luvrbus]

Behind the fan there is a disk to drive the fan maybe the springs have broken and are rattling around in the housing check for slop on the fan

[TomC]

Without a doubt-it is one of your Jake brakes firing off. Make sure the Jake brake is off. Good Luck, TomC

[OneLapper]

I agree with Tom, sounds like a Jake.  The oil pressure comes up and the Jake actuates.