You either have a leak or you have air in your system that you need to get out. What does the engine oil look like? Is it whiteish or frothy? How old is your radiator cap? Check the hoses in and out of the firewall for leaks, Get your car's front end up higher than the back. Not crazy high, but like the slope backing out of the garage into a driveway. Keep car running with the bonnet in service position, defroster on full fan and the windows closed door shut. Inspect the hoses, giving them a squish periodically while the car gets to temp. (thought bubble is I hope you are running the car with a thermostat) As the car reaches temp it may take longer as the coolant is flowing thru the heater core and the fan is blowing air thru it. Your Temp will get hot however, and if you have a thermostat in there if it is working..it will open and flow will be robust and the roar of the fan clutch will be noticed without fail (if it is working). Monitoring these hoses at the firewall, the expansion tank and the radiator all the while. If you do not have visible leaks then you may have air in your system or whitish frothy oil if you have a head gasket leak. If you have humidity evidence on your windscreen at temp, you may have a heater core that is suffering in some way. If it was leaking you would have musty sweet/sour mash smell perhaps with evidence of moisture blown on the inside windscreen near the defroster vents. Wile this is not likely your issue, running green style coolant can and has more often than not proven to eat away at the aluminum core and pipes as the coolant sits in those components during mild temps. Hopefully not your case. The over flow bottle in the PS fender well should be looked at. The original hose off the expansion tank into the fender well is hot and brittle over time and can be a leak source. It is just a tire removal and some fender liner nuts to remove to gain access there. if you have a hose leak it will be evidence of it very clearly. If the hose is brittle, any rubber hose from the local mcflaps store will do as long as the ID/OD are the same and the rating is proper for the fluid. Your need to pay attention to the circuitry of the hoses heading into and out of the firewall and also the washer tank reservoir and heating to the wiper system hoses/
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