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John, Master A.S.E Automotive technician
Category: Chevy
Satisfied Customers: 9176
Experience:  A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
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2000 impala: temp gauge will spike..trans fluid..therm..flushed

Customer Question

2000 impala 3.4 no heat and temp gauge will spike at times and then go down, oil and trans fluid not contaiminated.coolant had a brownish build up.Radiator and therm. replaced and system flushed but no change. Intake gasket replaced 20k ago.
Submitted: 8 years ago via
Category: Chevy
Expert:  John replied 8 years ago.


Use a class 2 scan tool to see the actual engine temperature when the gage spike is present to verify gage accuracy.

With engine warmed up & heater on,go under hood & feel both heater hoses.Are the both hot & close in temperature ? If not you have an obstruction in the heater core.If they are hot you most likely have a failed temperature actuator.There is usually a code set in the Body Control Module for this condition.

Customer: replied 8 years ago.
one side is hot the other side is warm, the heater core has been flushed and back flushed and appears to flow.
Expert:  John replied 8 years ago.
The most likely cause is a failed temperature actuator.Use a class 2 scan tool & look at the body control functions,along with failure codes to make sure this is your problem.

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