Hello,

After checking some threads about coolant overflow i want to share my experience too and if you can helm me with what is happening

I have a Koyo radiator with a spoon radiator 1.35bar cap and Mugen thermostat and fan shitch. While doing some work in my car i unpluged the radiator fan (the one closes to the overflow bottle) and forgot to plug it back. After couple of rides with my car i noticed when starting the car from cold the water temperature was rising a little more than 82 degrees Celcious, where the fans start kicking normally, so that made me curious and checked the engine. I saw the cooloant overflow bottle full and some coolant was out of the bottle in the engine. That was when i noticed the fan was unplugged and plug it back. I filled in the radiator with some more coolant. Since that time i am facing the same problem after couple of rides not every time. Only when i start the car from cold i see the water temberature rises fast above 82 degrees Celcius up to 95 degrees (saw max yesterday) without the fans kicking in that they normally do at 82 degrees. So as i am keep driving the temperature returns back to normal. Going up to 82 degrees fans kicking in and water temberature going down to 74degrees as it was normally working up to now. This stays like that even after some hard pulls. The overflow bottle though still keeps being overflowing with liquid and spills some in the engine bay.

So i need your opinion. Does this sound like air in the system or a blown headgasket (pressure goes to the cooling system)? The water temperature never climped to high,to blow the headgasket from overheating the engine, max i saw was 95 degrees through the AEM EMS, and there is no oil in the coolant.

Just to mention i have a fully build engine 9:1 compression using stock headgasket.

Thanks in advance
Chris

 

No one?

 

It could be several things.
The reason it continues to overflow is probably because you added more to the system.
You may have an air bubble in the vicinity of the thermostat or more likely the thermostat may be bad.

Look at the common things before running off like chicken little about blowing a head gasket.

I found topping off the coolant at the small back nipple eliminates bubbles in the system.

At this point, I suggest you adjust the volume in the overflow tank, purge the system and go from there. If it acts up again look into replacing the thermostat.

 

Thank you for your reply. There is definately air in the system cause i oppened the radiator cap after leaving the car the whole night and a lot of air came off the radiator. The problem is from where this air is comming. I will bleed the system definately but how can a bad thermostat create air in the system? It works fine for a couple of rides and after it happens only on startup where the water gets more hot than normal for a few minutes and after everything returns back to normal apart from the coolant overflow.

Thank you again for your reply

 

hmm, if you can bleed the system, and then the system starts to overheat again, i'd be thinking about it being a blown headgasket. Do you lose heat when this happens?