ok, I'm tired of this. My sc300 has now started overheating again. When I first got the car together, it did that since it needed the air pockets out of the system. Then about a month ago, I had to replace my radiator cap because it couldn't keep a seal for the system to pressurize. And now it is over heating again and I have no idea why. It came out of nowhere. Any clues? I feel like maybe the thermostat isn't opening or the clutch fan isn't being effective.. the heat stays normal, then it just shoots up at a certain point and stays right below the red mark. please help.. i have a week to fix this before i go back home for break from college.

 

how old is your radiator? i found with my car, where the radiator cap sits. the sprung part of the cap sits on a rim inside, if it doesn't pressurize that. it will leak. thusly causing your issue.

seems like a likely senario anyway.

 

dont let it stay below the red mark to start... get it shut down before you bhg..


verify that your ac fans are activating also. then check radiator cap, verify fluid levels to see if youre leaking. If not check thermostat also.

 

yeah, i know not to keep it right below the red mark line. I was almost back to my apartment so it wasn't there long. and i shut it off and coasted into my spot. its not leaking i'm sure, the overflow tank is completely full with coolant now :/ .I think it may be the radiator cap again tho. push down on one side of it and i can hear pressurized air leaving the system. I just don't want it to be the water pump bc idk how i would change it down at school.

 

you might still have an air pocket.

take the thermostat out drive around a week or so.
or
park up steep hills or car stands at the front

 

I have the same issue, but on mine, it turned out to be a bad headgasket.
I had replaced the radiator with new koyo radiator, OEM cap and I did timing belt shortly before this issue, so water pump, termostat were new as well, but my car still was slowly overheating, and occationaly puffing white smoke. The also have the MAC tools funnel radiator flush kit (those are awesome tools, this to ensure I do not have have any air pocket)
If yours does the same, my suggestion ... do compression check/test.
If you doubtfull about the thermostat ..I suppose you can boil it with pan and water to see if the valve open or not under high temp (the bad news is you need to drain your radiator and to pull the thermostat out)

 

Probably a BHG. Mine did the same thing and eventually just failed catastrophically.

 

I just hope it isn't a blown head gasket.. just replaced it over the summer with brand new arp head studs.. gah.. i'm going to check the oil tomorrow and see. and it only puts off smoke when it starts up since it's so freaking cold out. after that it's fine.

 

do you have the stock fan shroud around your fan clutch? are you sure your clutch fan is working properly? i would suggest getting a infared thermometer and check the temperature of the radiator, hoses and other parts of the cooling system. it is an easy way to diag hot spots and has been used to diag air pockets in the radiator in my own experience. hope that helps