The car: 2005, 42000 miles.

Sorry in advance for the lengh i was just trying to be descriptive. Out of no where my car started over heating on me and caught me very much by surprise. The first time it happened i was not getting any heat and thats when i noticed that my water temp was very elevated. I immediately shut the car down and tried to figure out why. After letting it cool for about 30 minutes i limped it over to a local shop where they checked the pump and stated it was good and preceded to change the thermostat. Right after i picked it up and started driving home i still noticed i was not getting heat but the temp was staying in normal, it preceded to start blowing heat and i thought the new fluid and everything just had to work itself into the system. I thought everything was good, even after a 20 minute city/highway drive to a bar to meet friends the temp seemed fine. Well on my way home from there i again noticed that the temp was raising above normal levels again (higher than halfway accross the dash gauge). I pulled over and shut it down and looked for leaks or anything that might tell me something but nothing did. After that i started back up and noticed that the temp gauge was fluctuating frequently to normal and elevating levels, sometimes making it uncomfortably hot and i would pull over for a few minutes which i only had to do about 2 times, but i noticed that if i kept the revs alittle higher it would keep the temp from shooting up, i also noticed that during acceleration the temp would decrease ussually and when deceleration it would increase which i did not understand. So i finally got it home. Does anyone have any idea what could be the problem with my cooling system?

 

Did you check if the fan was turning on?

 

Sorry to leave that little bit out. I have not noticed the fan turn on. on a side note, i drove it to work (15 miles) and the temp fluctuated between 7 and 10-11 bars for the first few minutes and then leveled out and stayed at normal operating temps for the majority of the drive.

 

Did you recently drain and refill the coolant? Sounds like you have an air pocket in the system. Search on here how to properly bleed the system, the S2K can be finicky to bleed.

Scott-

 

Could be a air pocket in the system as mentioned above or it sounds to me like your thermostat starting to fail. Sounds like its staying stuck closed then eventually freeing up a little after it over heats and unsticks. Your heater not working right points to the either of the above also. My guess though is the thermostat. Thats the only thing on my car thats actually failed so far since ive owned it and those were the things mine was doing prior to it completely failing. I first though i had an air pocket somewhere but after a pressure bleed didnt fix it i replace the thermostat and that solved the issue. After removing the failed thermostat i held it under a torch to heat it up and even with direct flame it wouldnt open up so it was definitely a goner.

 

the thermostat was just replaced and thats why i dont understand why i am still having this issue, im beginning to believe that it could be a air pocket in the system because the car is definetly driveable and have put some mileage on it, i just get very nervious when i see the temp flucuate to a hotter point.

 

No heat means that hot coolant is not getting to your heater core. Blocked core, stuck heater valve, thermostat stuck open, failed water pump, or an air pocket could cause that.

Over heating could be a thermostat stuck closed, failed water pump, fan not turning on, clogged radiator, or an air pocket.

I'd say you have a bad water pump, slipping belt or an air pocket. Seeing as it doesn't overheat when you rev it would lead me to believe that its the water pump or belt. The water pump is hardly turning or not turning at all at the lower revs. But somehow catches and turns just enough to keep the car from overheating at higher revs.

There are two spots where you need to bleed the cooling system. One is a small rubber cap on a coolant pipe behind the motor. The other is a 10mm hex bleed screw at the front of the motor on the intake manifold.

 

Sounds like a bleed (air pocket) problem to me.
Are you getting heat out of the cabin heater?
read this thread
https://www.s2ki.com/s2000/topic/876...ntengine-temps

 

when the car is cool open the radiator cap and turn the car on and run the heater on high , when you hit 2-3 bars and coolent is done gushing out the radiator cap turn it off and refill the overflow tank and thats how you properly bleed the coolent. worth a try.

if that doesnt work your pump or thermostat is stuck. or do you have a hole in your overflow tank?
people who race and drag their cars add more water than coolent because it cools faster, so check your water to coolent ratio. you can buy the tool for like 6 bucks at walmart. instead of a 50/50 mix try around a 60-65/50 mix and see if that improves it.

i have a hole in my overflow tank and water is always evaporating leaving more coolent than water, so i always run the heater and add more water in the overflow tank so it can properly cycle.

 

oh and i found a video of how to bleed the radiator for you! about 1/2 way
http://www.youtube.com/watch?v=_a6z5TbbEH8