Cavalier L4-2.2L VIN 4 (1998)
Coolant Temperature Sensor/Switch (For Computer): Technical Service Bulletins
Instruments - Erratic & Incorrect Engine Temp Reading
File In Section: 06 - Engine/Propulsion System
Bulletin No.: 99-06-02-010
Date: March, 1999
TECHNICAL
Subject:
Erratic and Incorrect Engine Temperature Reading
(Bleed Air from Cooling System)
Models:
1998-99 Chevrolet Cavalier
1998-99 Pontiac Sunfire
with 2.2L Engine (VIN 4 - RPO LN2)
Condition
Some owners may comment about low coolant temperature gauge readings and when performing diagnosis, the technician may notice coolant
temperature readings below the actual coolant temperature.
Cause
There may be a small pocket of air trapped in the coolant temperature sensor fitting on the radiator inlet pipe. This air pocket insulates the coolant
temperature sensor from contact with the coolant flow causing low temperature gauge readings.
Correction
REMOVE THE TRAPPED AIR WITH THE FOLLOWING PROCEDURE:
Caution:
With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at
atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil
instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious
bodily injury may result.
1.
With the engine off and at ambient temperature, slowly remove the surge tank cap to relieve pressure from the cooling system.
2.
Locate the Coolant Temperature Sensor on the Radiator Inlet Pipe.
Notice:
DO NOT APPLY TORQUE DIRECTLY TO THE RADIATOR INLET PIPE! Always use a back up wrench on the coolant temperature sensor
fitting to prevent damage to the Radiator Inlet Pipe.
3.
Observe the gap between the bottom of the hex on the coolant temperature sensor and the top of the hex on the fitting brazed to the radiator inlet
pipe. It may be helpful at this point to mark the coolant temperature sensor thread with a reference mark 5 mm (0.196 in) down from the bottom of
