CLOSED COOLING
SERVICE MANUAL NUMBER 30
7.
8.
While maintaining specified pressure on closed cooling section, visually inspect
external portion of cooling system (hoses, gaskets, drain plugs, petcocks, core plugs,
circulating pump seal) for leaks. Also, listen closely for bubbling or hissing; either
indicates a leak.
If no leaks could be found in above steps, engine is leaking internally, and it probably
is due to one or more of the following:
•
Loose cylinder head bolts or damaged gasket
•
Loose intake manifold bolts or damaged gasket
Loose exhaust elbow or distribution block retaining nuts or damaged gasket
Cracked or porous cylinder head or block
•
•
•
Cracked or porous exhaust manifold.
9.
Proceed as follows until location of internal leak is found.
a. Start engine. Re-pressurize system to previously specified amount and observe
pressure gauge on tester. If needle in gauge vibrates, compression or combustion
is leaking into closed cooling section from a leak in the combustion chamber.
b. Remove spark plugs (one at a time) from cylinders and examine for presence of
coolant. A spark plug that is perfectly clean or milky appearing is an indication of a
leak.
c. Drain oil from engine and examine for presence of coolant. Oil will be milky if coolant
is present. If coolant is present, remove engine from boat and drop the oil pan. With
engine in the upright position, re-pressurize closed cooling section to previously
specified amount and examine internal surfaces of engine to locate leak.
d. If no leaks can be found in the above steps, entire engine must be disassembled and
inspected for leaks.
Heat Exchanger
Testing And Inspection
INTERNAL LEAKS
An internal leak will cause coolant to go into the seawater circuit when pressure is put on
the closed cooling circuit.
1.
2.
3.
Remove a seawater hose from the heat exchanger. Do not drain the heat exchanger.
Pressurize the closed cooling system to 19 psi (131 kPa) with a radiator tester.
If seawater begins to flow from the hose fitting, there is a leak.
WATER BLOCKAGE
IMPORTANT: Seawater flows THROUGH the tubes in the exchanger. Coolant flows
AROUND the tubes.
1.
2.
Remove end caps and inspect for any blockage in the seawater circuit.
Remove closed cooling circuit hoses and inspect the tubes just inside the hose fitting.
The complete heat exchanger cannot be inspected; the heat exchanger should be
replaced if is suspected of being blocked.
INDEX
Page 6A-8
90-863161 SEPTEMBER 2000
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 496 CID |
| Model Year | 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
(2 votes, average: 4 out of 4)
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Great down load . it was all there an more