Strange overheating symptoms. - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

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

Quote:

Originally Posted by cerealwars

+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.

11-07-2014, 11:01 PM	#1
thordrivesfast Join Date: Oct 2014 Location: Coeur d'Alene Age: 31 Posts: 9 Trader Rating: (0) Feedback Score: 0 reviews	Strange overheating symptoms. 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.

11-08-2014, 11:37 AM	#2
angel mkiv Zilvia Addict Join Date: Sep 2009 Location: Seattle, wa Posts: 727 Trader Rating: (4) Feedback Score: 4 reviews	Only thing I could think of is sticky thermostat or you didn't bleed it correctly/all the way. __________________ Instagram username:angelmkiv

11-11-2014, 01:36 PM	#3
silverarrow27 Zilvia FREAK! Join Date: Oct 2005 Location: Banning, CA Posts: 1,428 Trader Rating: (11) Feedback Score: 11 reviews	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. __________________ 1989 240sx XE\|2002 Frontier SC CC LB 4wd\|2011 Pathfinder LE V8 4wd

11-11-2014, 01:42 PM	#4
cerealwars Zilvia Member Join Date: Mar 2011 Location: Detroit Age: 32 Posts: 161 Trader Rating: (5) Feedback Score: 5 reviews	+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. __________________ 93 coupe - AutoX/Fun summer daily/Eternal project

11-11-2014, 09:10 PM	#6
jr_ss Post Whore! Join Date: Dec 2005 Location: Pa Posts: 6,413 Trader Rating: (35) Feedback Score: 35 reviews	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. __________________ My SR20VET Does your VTC gear rattle in your S14/15 SR? PM me.