Flushed cooling system changed out thermostat. While driving no more than 5 miles temp gauge went up almost to red line then went back down. Noticed fluid bubbling out of radiator cap. Thought it just might be air so I let some air out. Drove again this time temp went high after not even a mile. What could be wrong? No leaks other than coming out of radiator cap.
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Re: Temp gauge goes up and down
First i would purchase a new radiator cap 15 lbs 16 lb capacity cost about $7..then you must let car cool completely...now check radiator coolant level.. top off if it needs it. Now install new cap..let car warm up normally and after it get to normal temp range or higher put hand on upper radiator hose..it should feel hot and when you squeeze it you should feel a slight back pressure..this will mean that the thermostat and water pump are working correctly. if not either the thermostat you purchased is defective or your pump may not be working properly. when you use just water in an engine the boiling point becomes 212 when you add the correct amount of antifreeze, depending on where you live, the boiling point will go up to 240 degrees. Make sure you put in the correct amount of mix.50/50 will usually work well. sometimes when a gauge does max out like that it could just be trapped air. if after you checked all this out and no air is trapped in the system, i would think that you may have a bad temp sensor. let me know if this helped thanks.
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1. Engine Coolant Temperature.
If the thermostat in the cooling system is getting stuck in the open or partially open position rather than opening and closing as needed to keep the coolant at the required operating temperature then you will get the results you have described here with the coolant temp dropping as you drive. The radiator is providing optimum cooling when the car is moving and there is plenty of cold air flow through it.
I am assuming the temp gauge in the vehicle is reading correctly.
Thermostats in the cooling system do become faulty in time and it may well never have been changed (or only changed once) since the car was built and is possibly gummed up with debris. With those symptoms I would definitely change the thermostat. Make sure a full flush of the cooling system is done at the same time and refilled with fresh coolant.
2. In Car Heater.
I would not worry about the interior heating until you change the thermostat on the cooling system. However if you continue to get cold air from the heater then there will be an issue with hot coolant from the cooling system being restricted in flowing through the heater core.
is the cooling fan cutting in ? run the engine whilst stationary with the hood up , give it a little gas 2000revs and wait for the temp gauge to rise ,the cooling fan should be heard cutting in , and off again once cooled the engine temp down ,this may take 10-15 mins but you have to be sure the fan is cutting in or you may cook the engine
do a full system flush on the radiator and engine and the lines to the heater. flush them out. also change the thermostat and the temp switch, the temp switch sensor is the one with only one wire on it with either a 11mm or 13mm head on it depending what one was fitted. after it is flushed reconnect the pipes add the water and antifreeze, when all clean in the system the water should come out clean. 50/50 water antifreeze should be used. leave the top off the header tank and run the engine with the heater on number one. keep squashing the pipes as the engine warms up to help get the air out and keep the header tank full to the top. when the fan kicks in to cool the rad turn off the engine and leave to cool down when cool top up to the line and put the cap back on. wile you are doing the bleeding you should see the temp go up. if the heat goes to or above a 100 and the fan does not come on then the fan switch or motor may need changing, thermostats last for around 5 years, temp switches can last up to 5 years temp switch for the fan can be around 3 to 8 years.
More than likely sounds like your heater core is bad or clogged, easy thing to do is have it backed flushed, also you may need to burp you cooling system it may have a air pocket due to the radiator change