Need some help, friends 85 Z28 thermostat is not working. The needle is stuck in high position in the morning when first turning the car over. Engine is cold and yet the temp reading is above 220 degrees. He replaced coolant thermostat and went as far as replacing the temp gauge. Still reading high from a cold start. Member has a code 32 and a 43. Any help would be appreciated.

 

wow, the exact same same is happening to my car...although im sure they are totally unrelated, im very anxious to see the replies you get to this post. code 43,32, and a sticking temp needle that sticks at first then goes to normal.....i will be checking this thread to see whats going on...

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As for the temperature guage, did he look at the temperature sensor in the driver's side head between cyl# 1 & #3? Try disconnecting it, it should go to 0. If it doesn't, I would suspect a short.

 

Glenn91L98GTA,
Thanks for your help. He replaced the coolant temp located in between spark #1&3. He set the connector on the plenum and started the car. The temp went up; he again relocated the connector somewhere else. (Reason being as he stated that the metal piece was touching his plenum) He put the connector on a rubber piece and started the car. The temp gauge read at 100 degrees and did not move. He let the car idle for 2 minutes and the temp needle still did not move. Connected it back to the sensor and the temp went up to 260.

 

Are you saying that it still reads max with the new sensor? Or are those the result of your testing prior to replacing the sensor?

If it still reads max, after you replaced the sensor, you are going to have to trace it back. You have a new guage and a new sensor. The problem is then in the wiring.

Take an ohm meter an measure the resistance of the sensor. It should show high resistance when its cold and less as it warms up. Then start tracing backwards. Good to get an electrical diagram. Make a post asking for a wiring diagram for your car. I'm sure someone has one available that they can post for you.

 

Ok the same kinda things happens to my truck. What I've discovered is that it's a sticking thermostat. The engine temp climbs even though it's just been started, then when the thermostat breaks loose the temp goes right down. I found that when I buy a new thermostat is helps to check the motion of it since the stamped parts don't always have the highest tolerances. Just a simple $3 part hosing up the works.

If you've ruled out this problem, other possibilities would include blocked passages or incorrect antifreeze mixture, maybe even a collapsed radiator hose. I'd check that thermostat again though.