ok so iono if the Guage itself or my cooling system..

ok... so i drive to work 5 days a week at 7:45 in the morning...i start the car let it idle for about 30-40 secs.. n then put it in drive. SC sometimes slams into gear.. (ill have to do OLT's Mod/Trick later when i have time) and just let my car run/idle down to the streets so the engine can still warm up without me gassing it (i drive downhill).. SOOO

heres the problem.. Whenver i drive downhill i notice my guage reads cooler than normal.. say when my guage is at quarter mark.. going down hill itll read cooler that quarter mark.. n then itll go back to normal later on..

ALSO...

ok so thats the car getting colder than normal.. it gets worse.. it gets hotter than normal as well.. ( or so it looks like on the needle)... ok so down the street... getting ready to get on the on-ramp to the 91 freeway.. i notice my gauge rising slowly up.. passed the mid mark where its supposed to be. i go on the freeway and it rises quarter till red.. im still trying to get to freeway speeds slowly to save gas heh.. and the needed rised till it touches red. a few secs later it drops back to mid/normal zone..

ok what seems to be the problem? its beed doing that since May, 08 i believe.
im thinking either there is a bubble.. or my thermostat is all crappy that closes when its not supposed to and opens when its not supposed to?

 

guess im the only one wit the problem... sigh...

 

I used to be in a similar situation. When ever I would take a hard right or a left the temperature would slowly rise or drop. I wanted to get to the bottom of this so I flushed my entire cooling system and noticed all the dirtyness that had built up in the system. My guess is you might have a dirty cooling system.

 

hmm sounds plausible. when i changed out my starter (this is a SC400 btw.)... i think some stuff might have fallen in the Coolant bridge... hmm

 

ok so my problem is getting worse.. like pretty bad.. today it went past red a few times n then down.. i was about to pull over on the side of the freeway.

i noticed though.... Whenever the temp guage shoots up my heater doesnt work. and when it falls back to normal my heater starts working...

this is kinda starting to scare me since i dont want to be stranded on the side.. especially since i dont have a cell phone anymore..

 

Same thing started happening to me about a week and a half ago, except it'll just go up and down at random, and not to the extent you described. I am going to flush my coolant system later this week, and I'll see if that helps any.

 

hmm i wanna flush but i dont have the time.. i leave home at 7ish am.. n come back at 9pm... for work -_-

ok so an update.. after work.. drove for a bit.. the heat guage just kepted climbing n climbing. It went down for a few seconds n then climbed some more.. a few minutes it went pass the RED.. n touched the "H" and didnt go down.. i decided to stop and popped the hood.. =/ all i saw was steam sigh...

i notice its steaming and hissing from the back.. near that heater switch.. passenger side.

sigh... the sc400 is out for now =/

 

uhh....change the coolant, man. Seems like you were running really low.

When you keep the rpms HIGH, does the temp go down? thats a dead giveaway you have air in the system.

 

blown headgasket? fyi: i would never let my engine get to the red. pull over immediately if the needle starts going anywhere close to the red.

 

i flushed n changed my coolant about lesser than a year ago. As for the RPM.. actually when my RPM's go up the heat goes up with it


hope it isnt =/ i tried not to.. i was hoping itll go down but it didnt so i pulled over sigh..


but yea when i turn on the heater.. it blows cold stuff while the temp rises n then when the heat starts blowing Hot.. the temp guage goes down..

wats do u think?

 

You might want to check your reserve overflow tank hose.
Make sure that radiator vent hose is connected to the overflow reserve tank inlet.
Temp gauge usually dances around if hose connection is loose.
Meanwhile, the radiator would spit out excess fluid instead of going to the reserve tank as engine heats the fluid.
Eventually, engine would overheat (lacking fluid) without proper reverve tank connection and cap.

 

My car was overheating whenever I turn on the AC, drive hard (high RPM).

new radiator, new fan clutch, new thermostat, and toyota red + dasani (didn't have distilled...)

My old radiator had all kinds of gunk inside and it runs like a champ again =D

 

i believe radiator overflow tank hoses are on right last time i checked (yesterday night cuz i had to pull over again..) but ill check again.

could the problem be due to a bad thermostat? since it seems like the fluid isnt circulating at all when the temp gauge goes up.