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Ask Dave Nova Your Own Question
Dave Nova
Dave Nova, Pontiac Technician
Category: Pontiac
Satisfied Customers: 19451
Experience:  ASE Master Certification. GM World Class Certification
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98 pontiac: mini van..that is overheating sometimes

Customer Question

i have a 98 pontiac transport mini van that is overheating sometimes. sometimes the fan will come on and sometimes it wont. changed the thermostat and still the same problem. what else could it be?
Submitted: 6 years ago.
Category: Pontiac
Expert:  Dave Nova replied 6 years ago.
How high does the temperature go?
Customer: replied 6 years ago.

it will go all the way in the red if u dont turn it off. if the fans are working it goes to 210. just redid the heads because of this overheating problem . van is running good besides when the fans decide not to work

 

Expert:  Dave Nova replied 6 years ago.
If you unplug the temperature sensor on the intake near the thermostat housing and run the engine, do the fans stay on all the time?
Customer: replied 6 years ago.
yes, they run even when its not hot
Expert:  Dave Nova replied 6 years ago.
If the fans will run everytime with the sensor unplugged, the problem is then most likely the coolant temperature sensor. If the fans still only worked intermittently with the sensor unplugged, the problem could be elsewhere.
Customer: replied 6 years ago.
i just changed the sensor and fans still not comming on they came on when i unpluged the sensor
Expert:  Dave Nova replied 6 years ago.
do you have a scan tool?
Customer: replied 6 years ago.

no i dont

 

Expert:  Dave Nova replied 6 years ago.
Try swapping the fan relay with one of the other relays in the underhood fuse panel to see if this makes a difference.
Customer: replied 6 years ago.
i switched the relay with the only other one i could find and it still didnt come on
Expert:  Dave Nova replied 6 years ago.
What does temperature gauge on the dash display with the sensor unplugged?
Customer: replied 6 years ago.
nothing. it goes all the way down below the lowest mark on the gauge. like its not working
Expert:  Dave Nova replied 6 years ago.
That is what it should do. The same sensor runs the gauge and sends a signal to the computer. If the gauge is working all the time, the computer should always be receiving the correct signal from the sensor. The problem will either be in the computer or the wiring to the fan relay. The computer is located under the air box for the air filter. Check the wiring around the computer carefully for chafing and/or damage.
Customer: replied 6 years ago.
the wires seem to be ok as far as i can tell. connections look good do u think i should try a new relay or it would most likely be the computer? how could i tell if it is the computer?
Expert:  Dave Nova replied 6 years ago.

You can test the circuits between the ecm and the fan relay. The best way to test is with a scan tool that show engine data. This way engine temperature can be monitored and cooling fan relay output can be checked.

 

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Customer: replied 6 years ago.
is the ecm the box behind and under the air filter?
Expert:  Dave Nova replied 6 years ago.
The ECM is in the box below the air filter.