Snap-On Diagnostics DGA 1000, Manual, Page: 106 / 116

6-12
Vehicle Testing Procedures
Combustion Gases in the Cooling
System Test
Use the cooling system of a vehicle as a window for evaluating the
condition of an engine when a blown head gasket, cracked engine
block, or cracked cylinder head is suspected. This test confirms
the presence of exhaust gases in the cooling system, but does not
pinpoint the exact source of entry. Use conventional tests to
identify the cause of the combustion leak.
• Coolant at high pressure and temperature can
escape from the radiator when the cap is
removed and during engine operation under
load. Use extreme caution when testing the
engine under load with the radiator cap
removed.
• Coolant under high pressure and temperature
may cause severe personal injury.
• Remove the radiator cap only with engine cold.
Testing Tip
X
Combustion gases leaking into the cooling system are usually
more easy to detect when the engine is operated under load
while sampling above the cap opening.
Test
1. Remove the radiator cap.
2. Hold the probe tip above the radiator filler neck.
Do not let the probe touch the coolant or draw
coolant into the sampling system. Liquid
contamination of the sampling system ruins
analyzer accuracy and can cause damage to the
system.
3. Note the
HC
reading.
Optional Test
Use this test method to eliminate the possibility of contaminating
the sampling system with coolant.
1. With the cooling system safely uncapped, place a plastic
bag over the cap opening.
2. Briefly run the engine to collect a sample of any gases that
may be escaping from the cooling system.
3. Insert the sample probe into the bag.
4. Note the HC reading.
Interpretation
• Any HC reading indicates combustion leakage into the cooling
system.
• Continue with conventional testing to pinpoint the exact source
of exhaust entry.