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View Full Version : Strange overheating symptoms.

thordrivesfast
11-07-2014, 11:01 PM
Whats up guys, im new on the forums. I purchased a 92 240sx SE that sat for a few years and ive been trying to freshen up the whole car. It is currently my DD. This past week i noticed when i am driving the temp will spike to close to the top of the gauge out of nowhere and drop back to halfway in the matter of a minute or less. Whenever i notice this happening i turn the heat all the way to 4 but the heater isnt even hot its more like room temperature. This is confusing to me because i just replaced: upper and lower rad hoses and clamps, thermostat, water pump. what else could it be? The coolant level is normal and i bled all the air pockets out of the cooling system after replacng the coolant. Maybe it could be my rad cap letting air in? idk what it could be. Any advice and or tips is greatly appreciated.

Thanks,
Thor.

EDIT: right before this problems started occurring the RAD FAN CLUTCH went out (seized) and i replaced it the next day with a NAPA part.
angel mkiv
11-08-2014, 11:37 AM
Only thing I could think of is sticky thermostat or you didn't bleed it correctly/all the way.
silverarrow27
11-11-2014, 01:36 PM
You didn't mention it, but have you checked if the coolant lines running into the firewall to the heater core is connected and correctly? Only thing I can think of since you said your heater blows room temps.
cerealwars
11-11-2014, 01:42 PM
+1 for heater core. Disconnect the lines at the firewall and blast a garden hose through it in both directions until clear water comes out.
thordrivesfast
11-11-2014, 07:37 PM
+1 for heater core. Disconnect the lines at the firewall and blast a garden hose through it in both directions until clear water comes out.
So are you implying it's clogged? I'm not really familiar with how the heater core works.
jr_ss
11-11-2014, 09:10 PM
Coolant flows through the heater core much like a radiator. The heat is then dispersed into the cabin via blowing air across the core. If you have no heat, you either have no hot coolant flowing through the core or no air blowing across the heated core. So you could have a blocked core or a bypassed core if you have air but no heat.