900 L4-1985cc 2.0L DOHC (1986)
Technical Service Bulletin # 03901221
Date: 900301
Heating - Flow of Heat From Heater Core Fluctuates
FILE IN
VOL.
S.I. Man.
I
SEC.
PG.
A-8
120
Subject:
Circulation Pump For The Heater System Issue: 03/90-1221
Application:
1985-89 900 Models
On certain cars with plastic heater control valves, the flow of heat from the heater core may fluctuate, depending on driving conditions. These heater
control valves have a constant by-pass flow and the heater core may not receive sufficient coolant flow at low engine RPM to provide a constant,
comfortable level of heat during certain situations, such as extensive stop-and-go driving in cold weather.
To remedy a persistent complaint about this problem a circulation pump may be installed. The pump starts when the ignition is turned on and supplies
the heater control valve and the heater core with a constant flow of coolant which in turn means that the passenger compartment temperature is not
dependent on engine RPM.
Before installing a circulation pump, investigate and remedy all other potential sources of insufficient heat output such as a blocked heater core, faulty
thermostat, etc.
NOTE
This kit will not remedy complaints of insufficient heat during highway driving, or driving conditions other than extensive idling and stop-and-go traffic.
There is sufficient coolant flow through the heater core at any engine speed above approximately 1500 rpm and the circulation pump will not improve a
complaint of poor heat at engine speeds above this level. This kit is not intended for 1990 models equipped with ABS.
Parts Required:
Pump Kit
P/N 41 18 063
Kit Contents:
Circulation Pump Wiring Harness Pump Bracket and bushing Self-tapping screw "T" fitting Hoses (qty 2) Hose Clamps (qty 6) Tie Straps (qty 5)
Pump Kit Installation Procedures
Figure 1.
1.
Disconnect the ground cable from the battery.
2.
Drain the engine coolant from the radiator drain.
3.
Remove the engine coolant expansion tank.
4.
Cut the tie strap which secures the hoses leading to the heater control valve (Figure 1).