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Discussion Starter #1
I looked at a 4bt today in a running ford F-250 pickup, the engine sounded great and showed very little vibration. The belt tensioner jumped alot at idle and smoothed out when revving the engine and you could also see the belt skip towards the block. Also when looking at the tensioner from the side I saw it move away from the block once. There was also an odd metalic "pop" sound that was random at idle and didnt do it at all when the engine was revved.

I looked at the FAQ section and found the tensioner problem to be somewhat normal but nothing about the noise. This truck had a manual tranny and the bread truck that it was originally in was also a manual...could this sound be from too much crankshaft end play? Also read in FAQ that there is a thrust bearing problem usually asociated with the manual trans motors.
This thing sounded and ran great except for the tensioner jumping and the random noise. I can get a pretty good deal on it but dont want to have to tear to far into it.
 

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I looked at a 4bt today in a running ford F-250 pickup, the engine sounded great and showed very little vibration. The belt tensioner jumped alot at idle and smoothed out when revving the engine and you could also see the belt skip towards the block. Also when looking at the tensioner from the side I saw it move away from the block once. There was also an odd metalic "pop" sound that was random at idle and didnt do it at all when the engine was revved.

I looked at the FAQ section and found the tensioner problem to be somewhat normal but nothing about the noise. This truck had a manual tranny and the bread truck that it was originally in was also a manual...could this sound be from too much crankshaft end play? Also read in FAQ that there is a thrust bearing problem usually asociated with the manual trans motors.
This thing sounded and ran great except for the tensioner jumping and the random noise. I can get a pretty good deal on it but dont want to have to tear to far into it.

You won't hear any noise related to a worn thrust bearing. If you want to check crankshaft end play, you can put a pry bar behind the crank pulley, and try to move the pulley forward. Do it gently, because the pulley is easily bent. You shouldn't notice much movement. Maybe .010". Then you can remove the starter, and try to pry the flywheel away from the engine. Also, you should get hardly any movement. Probably:) the tensioner is making the noise.--:)
Bob B.
 

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Occasionally a faulty valve spring or keeper/retainer will cause an intermittent mechnical pop sound yet the engine will run fine, until the valve spring causes sometimes serious problems.
 

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Occasionally a faulty valve spring or keeper/retainer will cause an intermittent mechnical pop sound yet the engine will run fine, until the valve spring causes sometimes serious problems.
A problem like a broken or weak valve spring, or retainer problem would not cause an intermittant noise at idle that goes away with an increase in RPMS. The valvetrain noise will get more pronounced as the revs increase.
Bob B.
 

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If I listen carefully to mine, I hear an intermittent metallic noise that I don't have an explanation for, too. I'd describe it as what you'd get if you smacked two wrenches together, but only if you held them firmly in the middle to eliminate any "ringing" after the hit. A metallic "thunk". It goes away if you increase the engine speed slightly. Also, it cannot be heard inside the vehicle.

No clue what it is, though. Might be worth running the engine without the belt on for a moment or two to see if it's accessory / tensioner related.
 

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My 6BT makes similiar noise at certain RPM, and gets better after it warms up. I know part of it is diesel knock, but it has some other noise if you listen real close....I think....or could be diesel knock. It seems to go away or drown out when you rev the engine past 1800-2k. I have decided it is nothing serious or I would have known it by now due to failure. The noise did not change when the head was changed and I have seen the bottom end and pistons which all appear good. I think these suckers are just noisey....


If I listen carefully to mine, I hear an intermittent metallic noise that I don't have an explanation for, too. I'd describe it as what you'd get if you smacked two wrenches together, but only if you held them firmly in the middle to eliminate any "ringing" after the hit. A metallic "thunk". It goes away if you increase the engine speed slightly. Also, it cannot be heard inside the vehicle.

No clue what it is, though. Might be worth running the engine without the belt on for a moment or two to see if it's accessory / tensioner related.
 

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A problem like a broken or weak valve spring, or retainer problem would not cause an intermittant noise at idle that goes away with an increase in RPMS. The valvetrain noise will get more pronounced as the revs increase.
Bob B.
Sorry, I was posting from personal experience, it can happen.

Could be the noise is one valve out of adjustment?
 

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When my 4bt was still in the chassis running I heard a simular noise as well.
The belt tensoiner looked as if it was slapping the the other pulley, I removed the tensioner and ran the engine for a few minutes, the noise was gone.
 

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Discussion Starter #10
Thanks for all the replies guys, it sounds like it may be worth taking a chance on this one. I'll keep you all informed if I get it.
 
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