Service Manual

ISB, ISBe and QSB (Common Rail [...] Air Compressor Carbon Buildup
Section 12 - Compressed Air System - Group 12 Page 12-9
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Remove carbon from the compressor head and valve
assembly components with a non-abrasive solvent and a
non-metallic brush.
NOTE: Using an abrasive solvent like carburetor cleaner
can lead to further lubrication loss in the air compressor
head.
Blow out passages with compressed air.
Verify the unloader slider plate is fully closed when at rest.
Remove the unloader slider plate and verify proper
unloader piston travel. Use a stiff wood handle or
equivalent non-abrasive device to move the unloader
piston by pushing back on the unloader slider plate guide
pin in the direction of arrow as indicated. Be careful not
to damage the aluminum surface of the head or drop
debris into the open slot in which the guide pin travels.
NOTE: When released, the unloader piston should return
to the loaded position (closed) with a quick, smooth
motion and audible snap.
If the unloader piston does not return completely to the
loaded position with an audible snap; fill the open slot
between the unloader slider plate guide pin and the
closed position of the unloader position with automatic
transmission fluid.
Actuate the unloader back and forth for three periods of
10 seconds. If the unloader is not free after 10 seconds,
fill the open slot again with automatic transmission fluid
each time until the piston is free and returns to the loaded
position (closed) with a quick, smooth motion and audible
snap.
If the unloader piston does not return to the loaded
position with a quick smooth motion and an audible snap
when released after performing the steps above, replace
the cylinder head.
Clean the compressor cylinder.
Rotate the crankshaft until the piston is at the top of the
cylinder bore.
Remove any accumulated carbon and varnish by careful
scraping and light application of solvents.