Yanmar 3JH4E Service Manual page 51

(4) Clean & check the water passages
When it is used for a long time, cleaning of the cooling water passages is periodically necessary,
because trash, scales, rust, and so on collect in the cooling water passages and the cooling performance
declines.
(a) Cleaning and inspection of cooling water rubber hoses.
1) Remove the cooling water rubber hoses for the fresh water line and the seawater line.
2) Check the dust and trash inside the hoses. If necessary, clean it.
3) Check the crack and the deterioration of the rubber hoses. If necessary, replace with new ones.
4) Replace the used hose clips with new ones, if necessary.
(b) Heat exchanger inspection
1) Cooler core inspection
a) Inspect the inside of the tubes for rust or scale buildup from seawater, and clean with a wire brush
if necessary.
NOTE: Disassemble and wash when the cooling water temperature reaches 85
b) Check the joints at both ends of the tubes for looseness or damage, and repair if loose, Replace if
damaged or corroded
c) Check tubes and replace if leaking.
d) Clean any scale or rust off the outside of the tubes.
2) Heat exchanger body water Leakage test
a) Check heat exchanger body and side cover for dirt and corrosion. Replace, if excessively
corroded, or cracked.
b) Inspect seawater and fresh water inlets and outlets, retighten any joints as necessary and clean
the insides of the pipes.
c) Check the exhaust gas intake flange and line, and replace if corroded or cracked.
3) Heat exchanger body water leakage test
a) Compressed air/water tank test
Fit rubber covers on the fresh water and
seawater inlets and outlets. Place the heat
exchanger in a water tank, geed in compressed
air from the overflow pipe and check for any
(water) leakage, (air bubbles).
b) Use of the tester
Fit the fresh and seawater inlets and outlets with
rubber covers and fill the fresh water tank with
fresh water. Fit a pressure cap tester in place of
the pressure cap, operate the pump for one
minute and set the pressure at 0.15MPa
2
(1.5kgf/cm , 21.33lb/in.
the pressure will not rise. If there are no leaks the
pressure will not fall.
2
). If there are any leaks
35
2. Inspection and Adjustment
°
Pressure gauge
Air hose
Filler cap
Rubber cap
Rubber cap
C.
Rubber
cap
Tast tank
Heat exchanger
Pressure tester
Pressure gauge
Rubber cap