Yukon Denali AWD V8-6.2L (2007)
Heater Core: Technical Service Bulletins
Cooling System, A/C - Aluminum Heater Cores/Radiators
Bulletin No.: 05-06-02-001A
Date: July 16, 2008
Information On Aluminum Heater Core and/or Radiator Replacement
2005 and Prior GM Passenger Cars and Light Duty Trucks (including Saturn)
2003-2005 HUMMER H2
This bulletin is being revised to update the Warranty Information. Please discard Corporate Bulletin Number 05-06-02-001 (Section 06 -
2004-05 Chevrolet Aveo (Pontiac Wave, Canada Only) does not use DEX-COOL(R). Refer to the flushing procedure explained later in this bulletin.
The following information should be utilized when servicing aluminum heater core and/or radiators on repeat visits. A replacement may be necessary
because erosion, corrosion, or insufficient inhibitor levels may cause damage to the heater core, radiator or water pump. A coolant check should be
performed whenever a heater core, radiator, or water pump is replaced. The following procedures/ inspections should be done to verify proper coolant
To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and
steam under pressure if the radiator cap or surge tank cap is removed while the engine and radiator are still hot.
If the vehicle's coolant is low, drained out, or the customer has repeatedly added coolant or water to the system, then the system should be completely
flushed using the procedure explained later in this bulletin.
Verify coolant concentration. A 50% coolant/water solution ensures proper freeze and corrosion protection. Inhibitor levels cannot be easily
measured in the field, but can be indirectly done by the measurement of coolant concentration. This must be done by using a Refractometer J 23688
(Fahrenheit scale) or J 26568 (centigrade scale), or equivalent, coolant tester. The Refractometer uses a minimal amount of coolant that can be taken
from the coolant recovery reservoir, radiator or the engine block. Inexpensive gravity float testers (floating balls) will not completely analyze the
coolant concentration fully and should not be used. The concentration levels should be between 50% and 65% coolant concentrate. This mixture will
have a freeze point protection of -34 degrees Fahrenheit (-37 degrees Celsius). If the concentration is below 50%, the cooling system must be
Inspect the coolant flow restrictor if the vehicle is equipped with one. Refer to Service Information (SI) and/or the appropriate Service Manual for
component location and condition for operation.
Verify that no electrolysis is present in the cooling system. This electrolysis test can be performed before or after the system has been repaired. Use a
digital voltmeter set to 12 volts. Attach one test lead to the negative battery post and insert the other test lead into the radiator coolant, making sure
the lead does not touch the filler neck or core. Any voltage reading over 0.3 volts indicates that stray current is finding its way into the coolant.
Electrolysis is often an intermittent condition that occurs when a device or accessory that is mounted to the radiator is energized. This type of current
could be caused from a poorly grounded cooling fan or some other accessory and can be verified by watching the volt meter and turning on and off
various accessories or engage the starter motor. Before using one of the following flush procedures, the coolant recovery reservoir must be removed,
drained, cleaned and reinstalled before refilling the system.
Using coolant other than DEX‐COOL(R) may cause premature engine, heater core or radiator corrosion. In addition, the engine coolant
may require changing sooner, at 30,000 miles (50,000 km) or 24 months, whichever occurs first. Any repairs would not be covered by your
warranty. Always use DEX‐COOL(R) (silicate free) coolant in your vehicle.
If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost would not be covered by your
warranty. Too much water in the mixture can freeze and crack the engine, radiator, heater core and other parts.