A25C noisy engine

[Brunelli77]

Can some one please.
Rebuild A5C engine. When building up air engine makes a noise around timing gear area.
As soon as air builds up noise goes away. Got front of engine apart cant see anything.

 

[Mobiltech]

Air compressor failing.

 

[sfrs4]

Air compressor is never disengaged so if it was the air compressor surly it would make noise all the time? does the noise sound like weights spinning in something and the noise goes away with oil pressure not air pressure? it could be your advance and retard timing device.

 

[Brunelli77]

I put brand new compressor.

 

[Brunelli77]

When air has build up to pressure noise goes away. I have the front cover and i still can't pinpoint the noise. I even went to the trouble of pulling the compressor gear off.
No noise. Sound like a timing gear noise. I checked the gears they seam ok.
Could it be the advance timing ?
It sounds like its coming from that area.

 

[sfrs4]

That is why I said it couldn't be the compressor it isn't switched or anything it's continually working, so the building up air pressure thing is either coincidence or a red herring, it's hard to describe the sound by words, but less of a rattle and more of a rhythmic noise, and like something spinning in something is the best way to describe the timing device failing

 

[Brunelli77]

When I pulled compressor gear off and run engine the noise goes away.
I am thinking the little bit of load from the compressor is triggering something.

 

[Brunelli77]

What does the timing device do?

 

[Mark250]

make sure the check valve between the compressor and the first tank is working correctly

 

[sfrs4]

Ok so if the load is what is stopping the noise then the rattle is probably coming from the head of the compressor there is a metal valve plate in there.

 

[Brunelli77]

I will check the valve tomorrow.
I will disconnect outlet line on compressor and run engine.
( i put brand new knorr bremse compressor on)

 

[Mobiltech]

Saying it could not be the air compressor is a little misleading.
The air compressor on a highway truck is driven all the time but It will go from rattling to quiet when the unloader dumps the pressure off the pistons. Usually a sign of slop in the pistons or rods.
I’m guessing you changed the compressor to try and get rid of the noise.
Did you check backlash in the gears?

 

[Shimmy1]

That is why I said it couldn't be the compressor it isn't switched or anything it's continually working, so the building up air pressure thing is either coincidence or a red herring, it's hard to describe the sound by words, but less of a rattle and more of a rhythmic noise,

I have an ISX in a truck that had the compressor replaced, and timed according to Cummins, and it rattles like crap when building air at idle.