i have a jap spec b16a in a eg6 and i noticed that if i drive my car hard, like on the highway..but then after get caught in traffic or have to idle for a long time..my temp needle goes up. and when i pop the hood i notice the fluid from the radiator gets pushed into the resevoir and i would have to pour it back into the radiator once it cools. can anyone tell me why its forcing the fluid back into the resevoir?

 

thats normal, and then when it needs more, it sucks it out of the resovoir.
Therman expansion. The coolant should come up to the cap at cold engine. Then as the temp gets to running temp, it expands and goes into the resovoir. When the engines gets a lil cooler, it sucks coolant from it. This should be above the min line at cold. Unless your cap is bad. Are you sure you don't have a leak? U using 50% water, 50% coolant? Is this engine you have hot, and requires more cooling than your radiator can do?

 

maybe even a bad thermostat?

 

yeah i that started to happen when my thermostat started to go out..it got increasingly worse, what you can do is take it out and test it by putting it in boiling water at 160 degrees and see if it opens up, of just replace it since its a 5-10 dollar part

 

i doubt its the thermostat because when i first bought the engine, i bought a new therm. just in case. but i didnt replace the cap...im not sure how the cap would cause the overheating but i'll try replacing it.

 

i dunno. if the cap is physically broken, like it wont let the fluid back in when it tries to suck more out of the resovoir. This is more powerful than your stock engine, if you diagnose this problem with no answer, maybe it just emits more heat. you can get a aftermarket radiator cap and thermostat, which open sooner, the fan will run more. Or you can upgrade radiators.

 

You have a blown head gasket dude. Hydrocarbon (unburned gas) is pushing out the coolant to the resovoir, causing it to overflow which makes you low on coolant hense the high temp. Change your head-gasket and you should be alright, if you haven't already warped your head . Don't upgrade your radiator or do anything with your thermostat, it's your head-gasket!

 

i was kinda wondering if it was the head gasket cuz i read some where it could cause that overheating problem...any idea what could of caused the gasket to blow? or how much it would cost to replace?