A/C - Cooling System Overheating/Heater Blows Cold: Overview
File In Section: 06 - Engine/Propulsion SystemBulletin No.: 99-06-02-012D
Date: April, 2002
TECHNICAL
Subject:
Rust in Cooling System, Heater Inoperative, Blows Cold Air, Engine Overheats (Flush Cooling System)
Models:
1996-2000 Chevrolet and GMC S/T Models (Blazer, Jimmy, Sonoma, S10 Pickup)
1998-2000 GMC Envoy
1996-2000 Oldsmobile Bravada
with 4.3L V6 Engine (VINs W, X - RPOs L35, LF6)
This bulletin is being revised to include additional model years. Please discard Corporate Bulletin Number 99-06-02-012C (Section 06 - Engine/Propulsion System).
Condition
Some customers may comment that the heater is inoperative, blows cold air, engine may exhibit an overheat condition or the coolant reservoir has rust in it.
Cause
Vehicles equipped with DEX-COOL(R) coolant, which may have been operated for extended periods of time with a low coolant level, usually in excess of 32,000 km (20,000 mi), may be susceptible to the formation of a rust-like material in the cooling system.
Correction
Flush the cooling system using the repair procedures that follow.
Parts and equipment required/suggested for this correction are listed below.
^ 1 each *Prestone(R) Flush and Fill kit # AF-KITP U.S. (# 00050 in Canada). This kit can be obtained from your local parts supplier and can be used on all vehicles repaired under this procedure. Save it after performing the repair, as it is reusable.
^ 1 each *Prestone(R) Heavy Duty Cooling System Cleaner, GM P/N 12346500 - 1 per vehicle. This cleaner is in powder form and contains a neutralizer. Do not substitute other cleaners. The diluted cleaners that are available in liquid form are not recommended for this repair.
^ 5.7 L (6 qt) of 100% (non-diluted) DEX-COOL(R) coolant (GM Spec 6277M).
^ 1 each new thermostat, GM P/N 12563335.
^ 2 each new radiator cap, GM P/N 15075565. 1 each *Prestone(R) yellow funnel. This funnel can also be obtained from your local parts supplier. It fits snugly into the radiator opening for an easy fill and is reusable.
* We believe this source and their products to be reliable. There may be additional manufacturers of such products. General Motors does not endorse, indicate any preference for or assume any responsibility for the products from this firm or for any such items which may be available from other sources.
Important:
Verify the fuel level in the fuel tank. The fuel level should be above 1/4 tank before this procedure is started.
As a precaution, verify the oil level in the crankcase. Add the amount required to bring the oil level into the normal range.
It is recommended the vehicle be placed in a position so that the following are available:
^ A sanitary sewer - not a storm drain, etc.
^ A monoxivent system (if the outside temperature is less than 10°C (50°F)).
^ Hot running water
Notice:
Due to the complexity of these procedures, the following repair steps must be strictly adhered to in order to achieve the intended results. Any deviation or substitution may result in sub-standard cleaning/flushing results or system damage.
Diagnostic Procedure
1. Install the Scan Tool. This will allow monitoring of the coolant temperature throughout the procedure.
Caution:
As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the radiator cap while the engine is hot and pressure is high will cause the solution to boil instantaneously - possibly with explosive force - spewing the solution over the engine, fenders and the person removing the cap. Under some conditions, the engine coolant is combustible.
Important:
^ The installation of a NEW radiator cap at the beginning of this procedure and the second new cap at the end of the repair procedure is necessary in order for the correct pressure to be achieved and for the repair to be completed successfully.
^ The radiator cap is NOT a good indicator of the general condition of the cooling system. Typically the underside of the radiator cap will exhibit a greater amount of contamination than the rest of the system. It is important to evaluate the condition of the cooling system by checking the following before beginning the repair procedure:
2. Remove the radiator cap. Install a new radiator cap, GM P/N 15075565. A properly operating radiator cap is essential for this procedure to work properly. Be sure to wipe off all radiator cap sealing surfaces prior to installation.
3. Start the engine.
4. Using a flashlight or lead light, look into the radiator. From the right side of the vehicle, peer into the radiator toward the left side of the vehicle. Observe the top three rows (or tubes) of the radiator. (It may be necessary to drain off some of the coolant to see the top three rows of the radiator).
If it appears the coolant is able to flow through the third row down from the top, the vehicle should be repaired using Procedure A. If it appears the coolant is NOT able to flow through the third row down from the top, then the vehicle should be repaired using Procedure B.
5. Stop the engine.
Parts Information
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use the table shown.
This is a unique labor operation for use only with this bulletin and will not be published in the Labor Time Guide.
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