2003 chevy trailblazer cooling temp running 230

I guess that depends on what 3/4 is temperature-wise. Engines normally operate in the 180-210 degree F range depending on the thermostat and whether there is a mechanical or electric fan. Mechanical fans keep the temperature more stable. If you feel that after what you have done that the temperature indication is still too high, the issue may be with the sending unit for the temp gauge or the gauge itself. Have the coolant temperature checked with a second temp device if possible, otherwise, try the sending unit first and see what happens.

With due apologize I do not know about the model year, engine code and other specs of your car. But check the following to solve the problem.
- Check Tire inflation.
- Check the clutch and pressure plate (if manual transmission).
- Check the accuracy of temperature sending gauge. (the fan should automatically start when the temperature gauge reads center position position on the combination meter.
- Check the radiator fan air flow, throw pressure and fan direction (should throw the air inside towards the engine).
- Check radiator cap and reservoir for air leaks. Perform cooling system pressure test.
- Check all the radiator hoses for firmness. Any scale or coolant color can reveal the leakage.
- Re torque all the cylinder head bolts a little more.
- Check color of engine oil. If the color is seen brown or excessive pressure is built inside the cooling system, due to the exhaust gases released into the cooling system, the cylinder head gasket is burnt. If so replace the gasket and surface grind the cylinder head with a surface grinding machine.

The powertrain computer turns the fans on through the cooling fan relays, based on information from the coolant temperature sensor. The fans will only come on when the coolant temp. is pretty high-varies by manufacturer, but it is over 200 degrees, some as much as 230 degrees. So the fans will not come on when engine is started, but they should come on before the engine overheats. You should have them checked. Also find out if the temp. gauge sending unit is separate and different from the coolant temperature sensor-on most cars, they are separate, maybe not on yours?
Free advice from a shadetree-not worth a lot, eh? lol.

Have you checked your cooling fan to see if it is working propely? Let the car idle and get warm and listen for the fan to kick in (if they are electric) or just watch to see if the fan starts to spin faster if it is the old school type with a clutch. Have you replaced the thermostat? A bad one will let the temp rise since it opens too late and then the temp will drop off. But it won't due this only at a light and it will do it infrequently.

Did the engine overheat before the water pump was replaced? If so, you may have a warped cylinder head and/or blown head gasket.

Was the radiator full of rusty-colored liquid before you flushed it? If so, your radiator is probably restricted with rust deposits in the cooling tubes. Flushing WILL NOT get this stuff out. The radiator MUST be replaced if this is the case. Your heater core is probably not in real good shape either, so you should be expecting some heating problems this winter.

If the above is not the correct answer, then you should check to make sure the temperature gauge is not "LYING" to you. This could be caused by a defective gauge, a bad temperature sending unit, or faulty wiring.

The way to check this is with a scan tool that can read engine data and an infrared thermometer. While reading the coolant temperature data from the computer, check the cylinder head temperature with the infrared thermomometer. The readings you get should be within 5 degrees (F) of each other. If the computer data does not match the thermometer within the 5 degrees, then the sending unit for the computer should be replaced.

Then look at the gauge to see if the gauge reading is appropriate to the temperature readings that you took. Normal operating temperature is between 190 and 230 degrees. This should place the gauge at slightly to the right of center to about 5/8ths of the way to HOT. If the readings you took are OK and the gauge is reading higher than this, then you should try replacing the temperature sending unit for the gauge and see if that fixes the problem.

Please note that there are TWO temp sending units: One for the gauge and one for the computer.

either the thermostat is getting ready to fail or the temp sensor isnt working properlythese engines also leak fluid from rear side of head after getting hot so check that so may have air in system because of the blown head gasket

Your sending unit is definately bad running at 180 - 210 is perfectly fine and it is not overheating at all.Replace it and your problems will be solved. But make sure you are using your lazer temp gauge at the same point as your temp sending unit.If you are then it is your sending unit if not you may have air in the system at the point of the sending unit and this will cause your problem as well.

You probably need to bleed the cooling system properly.

Open the cooling system bleeder screws.

Slowly fill the cooling system with a 50/50 coolant mixture until coolant runs freely out of bleeder screws.
Close the cooling system bleeder screws
Install the coolant pressure cap
Start the engine.
Run the engine at 2,000 - 2,500 RPM until the engine reaches normal operating temperature. (midway on gauge)
Allow the engine to idle for 3 minutes.
Shut the engine off.
Allow the engine to completely cool.
Top off the coolant as necessary.
Run engine again at 2000 - 2500 RPM until the engine reaches normal operating temperature.
Allow engine to idle until cooling fans come on. It should come on with the gauge about 3/4 of the way to red. - if it gets to where is touches the red, shut down immediately.
When the fan comes on, put your hand behind the fan and observe the temperature of the air coming from the fan. It should feel hot. If it is blowing cold air, the coolant is not circulating through the radiator like it should. This could be caused by lots of things including an improper/defective thermostat, corroded water pump impeller, or a blown head gasket.

Replace the thermostat. I have had bad luck with aftermarket thermostats on this particular year of GM/ Chevy trucks.They tend to stick closed and then fully open, thus causing the temp to sort of surge hot and cold. A good thermostat will slowly open maintaning a good consistant temp. I would recommend spending a little more and getting a GM thermostat.


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