At idle. I know the cam spins at half engine speed. I'm trying to diagnose some bearing noise. Only happens when the engine is warmed up. When it's cold the noise is not present. And off idle I can't hear the noise. It is very apparent at idle and can be heard from at least 15 feet away.
So far I know that:
The noise has a frequency that could be lined up with cam speed (350 rpm or thereabouts).
Water pump is new, cam belt tensioner is new. Distributor cap and rotor are also quite new. I did not think to check the intermediate shaft for play when I had the chance. The head has been off and flattened and refreshed since the noise started (no change to noise) but I don't trust that the guys who worked on it would have seen a cam bearing problem if there was one, especially since noise is only present warmed up. And I had evidence when I got the head back that they're not too bright.
I do have a stethoscope, but all I can tell with it is that the noise is somewhere on the front of the engine. I can hear the noise quite well on the engine lifting bracket, not quite as well on the front of the head casting, and about the same on the block right above the intermediate shaft. I can also hear the noise if i put the steth on the distributor boss, but not as loud as at the forward end of the intermediate shaft.
The engine has 164k miles on it. No other running problems. Runs very well actually.
edit: I also know that the noise is not caused by an accessory. I ran the engine (while warmed up) very briefly with all the belts removed and the noise was still present.
So far I know that:
The noise has a frequency that could be lined up with cam speed (350 rpm or thereabouts).
Water pump is new, cam belt tensioner is new. Distributor cap and rotor are also quite new. I did not think to check the intermediate shaft for play when I had the chance. The head has been off and flattened and refreshed since the noise started (no change to noise) but I don't trust that the guys who worked on it would have seen a cam bearing problem if there was one, especially since noise is only present warmed up. And I had evidence when I got the head back that they're not too bright.
I do have a stethoscope, but all I can tell with it is that the noise is somewhere on the front of the engine. I can hear the noise quite well on the engine lifting bracket, not quite as well on the front of the head casting, and about the same on the block right above the intermediate shaft. I can also hear the noise if i put the steth on the distributor boss, but not as loud as at the forward end of the intermediate shaft.
The engine has 164k miles on it. No other running problems. Runs very well actually.
edit: I also know that the noise is not caused by an accessory. I ran the engine (while warmed up) very briefly with all the belts removed and the noise was still present.
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