Heater - Fluctuating Output
90saab08Subject: Bypass Valve for the Heater System
Application: 1985- 900 Models With 16-Valve Engines
CATEGORY Body
SECTION PAGE
8 11
ISSUE CODE
11/90-0072 854
Figure 1:
On certain cars with plastic heater valves the flow of heat from the heater core may fluctuate depending on driving conditions. The heater control valve has a constant bypass which may result in insufficient coolant flow at low engine speeds to provide a comfortable level of heat during certain situations, such as stop-and-go driving.
An auxiliary bypass valve has been developed to help remedy complaints of fluctuating heater output. The service kit is designed for use on cars wfth 16-valve engines, with or without ABS brakes. The previously-released kit containing the circulation pump (see PSI 03/90-1221) should henceforth only be installed on cars with 8-valve engines, -M88. To further assist the operation of the bypass valve kit a 89~C thermostat, P/N 88 17 298, may be installed in place of the standard 82~C thermostat, P/N 88 17 538.
Before installing the bypass kit, investigate and remedy all other potential sources of insufficient heat output such as a blocked heater core, low coolant level, faulty thermostat, etc.
NOTE
This kit will not remedy complaints of insufficient heat during highway driving or driving conditions other than stop-and-go traffic. There is sufficient coolant flow through the heater core at any engine speed above approximately 1500 rpm and the bypass valve will not improve a complaint of poor heat at speeds above thls level.
Heater Bypass Valve Kit, B202 Turbo 41 21 745
^ Bypass Valve 40 73 706
^ Hose, water pump/pipe - bypass valve 41 21 729
^ Hose, lower control valve - bypass valve 41 21 703
^ Hose, upper control valve - bypass valve 41 21 695
^ Hose, coolant pipe - bypass valve 41 21 711
^ Hose clamps (Qty. 4) 79 70 080
^ Tie strap (Qty. 1) 79 71 880
Heater Bypass Valve Kit, B202 Nat. Asp. 41 21 687
^ Bypass Valve 40 73 706
^ Hose, water pump/throttle housing - 41 21 737 bypass valve
^ Hose, lower control valve - bypass valve 41 21 703
^ Hose, upper control valve - bypass valve 41 21 695
^ Hose, coolant pipe - bypass valve 41 21 711
^ Hose clamps (Qty. 4) 79 70 080
^ Tie strap (Qty. 1) 79 71 880
Figure 1:
Heater Bypass Valve Installation Procedure
1. Disconnect the ground cable trom the battery.
2. Drain the engine coolant from the radiator drain.
3. Cut the tie strap securing the hoses leading to the heater control valve. Remove the hoses from the control valve (Figure 1).
Figure 2:
4. Remove the lower hose from the large coolant pipe located between the intake manifold runners (Figure 2).
Figure 3:
5. Turbo models:
Remove the upper hose from the water pump and the small coolant pipe underneath the intake manifold (Figure 3).
Naturally-aspirated models:
a.) Remove the hose from the bottom of the AIC valve to the throttle housing.
b.) Remove the upper coolant hose from the water pump and throttle housing fittings.
Figure 4:
6. Turbo models:
Install hose clamps loosely onto hose 41 21 729. Fit the hose onto the water pump and the small coolant pipe undemeath the manifold (Figure 4).
Figure 5:
Naturally-aspirated models:
Install hose clamps loosely onto hose 41 21 737. Fit the hose onto the water pump and throttle housing.
7. Install hose clamps loosely onto hose 41 21 703. Fit the straight end onto the lower fitting of the heater control valve (Figure 5).
Figure 6.:
8. Install hose clamps loosely onto hose 41 21 695. Fit the straight end onto the upper fitting of the heater control valve (Figure 6).
Figure 7:
9. Install hose clamps loosely onto hose 41 21 711. Fit the long end onto the large coolant pipe between the intake manifold runners (Figure 7).
Note
Ensure that the throttle cable and, where applicable, the kick-down cables are routed in their original positions.
Figure 8:
10. Install the bypass valve (Figure 8). Ensure that the hoses are not likely to chafe anywhere before tightening all hose clamps. On naturally-aspirated cars, refit the hose for the AIC valve.
Figure 9:
11. Install the tie strap to secure the upper heater hose to the AC hose (Figure 9).
12. Reconnect the ground cable to the battery.
13. Fill the cooling system and bleed. Run the engine at normal operating temperature and check for leaks.
Warranty Information:
For warranty claims, use Failure Coding 26160-71-9-01-10. Labor allowance is Operation No. 26160 (0.5 hour).