just acquired a evo 8 this past december. ive put about 5k miles on it since ive had it. i had to replace the radiator cause the oem was leaking. i put it a mishimoto rad with oem mitsu. fluids. for the past two months my cars has had a very weird over heating issue. when i start up and let it warm up the car, after 5 mins of driving the temp gauges goes over pass the mid-range heat to about 3/4 of the way up, which is pretty high. if i just start up the car and let it sit for about 25-30 secs and drive off, after about 5 mins the temp shoots up to about 7/8 of the way up, after it does this te car drives fine all day.

 

To me this sounds like your water pump could be on the way out, might need a new one?

 

Before you replaced the oem radiator with the mishimoto was the car overheating ?

 

It could simply be an air bubble in the system causing the over heating issue which may only be reflected on the thermostat placed thermocouple. can you log the coolant temp thru evoscan to verify if its actually over heating?

 

thAnks for the replies yalls, i was starting to lose hope.

gzr: the water pump, and timing belt was replaced in september just before i bought it in late december. says the old owner with reciepts of labor and parts install.

a-917: no. the car ran fine. this issue has just risen since march.

dtrt-pstn: ive bled the system 3-4 times, how i did it? took the rad cap off started the vehicle, wait for the car to warm up enough til the fan kicked in rad fluid went down a little bit, added some coolant so it filled all the way up, then i revved the car till the rad fluid starts to go down again top then it off with the engine still revving i close the rad cap. dont have a logger unfortunatley, im new to the evo game so i have no clue which electrical set up to go with. is it possible to find out if its the thermostat by completely removing it? also my ac condensor fan does not work.

 

whats a thermocouple?

 

I'm not familiar with coolant flow direction, however could this be a sticking or ill responsive thermostat?

Does the mishimoto radiator have any bent tubes or possible obstructions?

 

i dont think the mishimoto is bending my tubes at all. if it is its not pinched.

i ordered a new t-stat as of last night

this morning was cold so i decided to roll down the window and turn the heater on. the car didnt over heat. at all until i tried to shut off the heat. temp started rising so i turned the heater back on and it went back down

 

get the t-stat done asap... tell us all why this previous owner was selling the car and what else is on it. What exactly do you mean by overheating-- does it peg the temp dial...has it ever? If so your looking at a head gasket. Has the GH recently been replaced?

 

I recommending installing an OEM radiator in the vehicle and properly bleeding the cooling system. After that, report back. Your thermostat may need to be replaced if you still have issues.

 

Here is my suggestion. Change the Tstat to an OEM (180) or Ralliart (170) . Get a coolant funnel like this that goes onto the radiator
http://static.cargurus.com/images/si...088327729.jpeg

Fill the coolant and start the car up. Turn the heat on high ( it should also get hot) and let the car run for about 20 min. While its running make sure the fan cycles on and off correctly. Gently squeeze a hose every few minutes and rev the engine a little . Let it idle another 10 and see if any more bubbles come up. This should burp the system.
If the fans don't come on you will need to look at the fuses and relays . Then the fan itself. Also, if you press the A/C button with the fan motor on it should turn the cooling fans on as well.

If everything checks out and it still gets hot you will need to log or get a Infrared temp gun and check the temps. If you still have an issue then you should do a pressure test on the system to see if the headgasket is intact. Good luck with it.

 

+1 on purchasing the yellow funnel as Abacus suggested.

 

sounds like a thermostat problem. every time i do radiator or deal with replacing a hose there i just do it anyway, its 25 dollar insurance from extremepsi.

 

Someone on here had a similar issue. It ended up being a wiring issue with the temp sensor for the gauge. They got water on the pins and when they cleaned and dried them all was fine again.

You have one sensor for the cluster, the other temp sensor for the ecu. You can get a scan tool, or use evoscan to see what the temp sensor to the ecu is reading. If that's fine then check the wiring and condition of the pins for the temp sensor to the cluster.

You can also look at the coolant values on evoscan and then also use a IR temp gun and point it at the thermostat housing. They should be somewhat close to each other, at least for diagnosing purposes. They will be close enough to at least let you know the sensor is working correctly or not.

 

Remove the thermostat to see if it is it first, If it isn't that could be the head gasket? Check the oil dip stick if there's any water in contact with the oil.