Heater - Insufficient Heat
File In Section: 1 - HVACBulletin No.: 46-11-02
Date: November, 1994
Subject:
Insufficient Heater Performance (Install New Water Pump and Re-Route Heater Outlet Hose)
Models:
1990-94 Chevrolet and GMC Truck G Vans with 5.OL and 5.7L Engines (VINs H, K - RPOs L03, L05)
Condition
Some customers may comment on insufficient heat during cold weather operations. The heating system may be performing properly; however, the customer may still be dissatisfied.
Cause
Inadequate warm up time from the heating system. In extreme cold environments, the heating system may be unsatisfactory if the vehicle is equipped with only a front heating system. It may be necessary to install a second (rear) heating system.
Correction
Install a new water pump which will need a 1 inch long steel nipple, and re-route the heater outlet hose to the new water pump. This will improve the warm up time for the heating system.
Service Procedure
Before installing the new water pump and re-routing the heater outlet hose, make sure that the heating system is functioning properly. There are a variety of options which may effect the heating performance.
First, perform a function test. Before performing the function test, make sure that the engine coolant is hot and thermostat is open. This function test procedure is located in the Service Manual Section 1A.
Check and verify that the following items are functioning properly. If not, repair as needed.
^ Low Coolant
^ Actuator mode door (temperature lever)
^ Thermostat
^ Waterflow obstructions
^ Airflow obstructions
^ Blower Motor Assembly
If the Heating system checks out to be functioning normally, install the new water pump (presently used on 4.3L engines) and reroute the heater outlet hose from the radiator to the water pump assembly.
Removal Procedure
1. Drain Coolant
2. Remove water pump assembly.
3. Remove the heater outlet hose. There are 2 methods of routing. Reference (Figure 1) for the Old routing. Once the hose has been removed, it will be necessary to save approximately 3 inches of hose material. This will allow the radiator side of the connection to be plugged.
Installation Procedure
1. Install steel nipple to water pump. Before installing the steel nipple, seal threads with pipe sealant (P/N 12346004) or equivalent. Torque to 24 N-m (18 lb.ft).
2. Install water pump.
3. Install end cap plug into remaining hose and install onto the radiator. Fasten securely with hose clamps.
4. Install new heater outlet hose routing it to the water pump (Figure 2). Fasten securely with hose clamps. Make sure that the hose has a clean routing. Make sure that the hose does not rub or contact any sharp edges. Secure with tie wraps if applicable.
5. Install remaining accessories.
6. Fill coolant to normal operating levels. Start engine and inspect for leaks.
7. Perform function test. Verify that coolant levels are at normal operating levels, engine hot and thermostat is open.
8. Check the coolant levels one more time. Fill to operating levels if applicable.
Parts Information
Parts are expected to be available from GMSPO on 11/14/94.
Warranty Information
For vehicles repaired under warranty, use:
