At what temperature should the coolant be to not be harmful to my 1998 Cadillac deville
Normal operating temperature should be between 160 and 190 degrees depending on what thermostat you have installed. If it is running much hotter than 190 then you need to service your cooling system.
Normal operating temperature for your Cadillac is 195°F. The engine must reach that temperature within a predetermined time from cold start up or the check engine/service engine soon light will come on and a trouble code will set. As you drive the temperature may fluctuate between 195°F and about 205°F. In stop and go traffic, in the summer, with the a/c going it may climb to 220°F. This is normal. Anything higher than that means there's something going on with the cooling system that needs to be addressed. HTH. -Jim
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