Coolant flowing out of cap

amf201091

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So i have a 98' gt thats a dedicated track car. I put a mishimoto radiator along with a new t-stat not to long ago. It has a moroso expansion tank. Everytime when the car is hot and i spin out off track or come to a stop... coolant shoots out of my cap! Ive replaced the cap with a new one (16psi/1bar) from autozone but still does it. Any ideas on what i should do? 19psi cap? Am i overfilling expansion tank? Theres no level with moroso's so i only fill it about half way when cold... help! Lol
 

OpalFrostGT

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Heat impacts pressure. Your problem is NOT pressure, pressure is a symptom of the actual cause!
Determine what is getting too hot
A. Is the Mishimoto radiator undersized?
B. Are your cooling fans not moving enough airflow to assist the radiator?
C. Is there some blockage in front of the radiator?
Whatever it is...it will be simple. Cooling down a radiator is simple. Don't overthink about it.
Again, I believe that pressure is a result and NOT the cause of the problem.
I would talk with some racing mechanics. Good luck with this issue. Keep us posted.
 
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The factory degas bottle has a full line on it and it is damn near the top maybe a half inch before the top of the bottle not the top of the cap. I'm not saying that is the problem but would fill it just like the stock unit. For peace of mind, I would drain the coolant just the radiator but not the block. Then if you have a coolant system vacuum/fill tool go ahead and pull a vacuum on the system and then use the suction hose coming from the tool and suck up the coolant you drained in a clean pan to refill your system. Try that first so you know for a fact you have no air in the system and fill the degas bottle as close to stock height. What brand and temp thermostat are you using?
 

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