08 Civic EX Overheating

[SnakeChamer]

145K miles, warranty short block replacement at 95K miles due crack.

Symptom: coolant is being forced out of the system through the reservoir/overflow. Engine compartment gets really hot but engine temp gauge never says above normal. Gurgling can be heard as coolant is exiting the system. No leaks anywhere. Not smoking out the tailpipe. Oil not a milkshake. Both fans functioning. Mechanic thinks it has a failing headgasket causing the cylinder compression to force the coolant out of the system.

Your thoughts/opinion, please.

 

[Brak]

cooling system works by creating pressure, which prevents the coolant from boiling.
if there is a leak somewhere, that constant pressure is not maintained, the coolant will expand, and fill up the reservoir, or overflow.

Commonly the main culprit is a failing radiator, water pump, or hoses/gaskets.
A leak on the top side of the system could cause pressure loss, without any noticeable coolant leakage, but most likely there's coolant leakage someplace.

head gasket is a possible option. if it's leaking near one of the outer edges, it wouldn't necessarily make it into the engine oil, hence your observation of no milkshake.

Realistically, if there's no visible coolant leak, the best way to pin point it would be a pressure test.

 

[SnakeChamer]

cooling system works by creating pressure, which prevents the coolant from boiling.
if there is a leak somewhere, that constant pressure is not maintained, the coolant will expand, and fill up the reservoir, or overflow.

the main culprit is usually a failing radiator, but a leak on the top of the system could cause pressure loss, without any noticeable coolant leakage.
head gasket is a reasonable option. if it's leaking near one of the outer edges, it wouldn't necessarily make it into the engine oil, hence your observation of no milkshake.

Realistically, if there's no visible coolant leak, the best way to pin point it would be a pressure test.

Thanks for your reply.

 

[nd4sped]

If there are NO leaks, seems like a failed radiator cap. The cap is what maintains a specific pressure (about 14-16 lbs) on the cooling system.

The pump will supply the pressure via flow, but he cap will maintain it. If pressure exceeds due to increased heat then the cap will release coolant into the reservoir. Make sure to NEVER overfull the reservoir as it will then push out of the overflow bottle.

Again if there are no leaks, swap out the radiator cap and ensure the proper level in the reservoir.

Let us know!

 

[Brak]

radiator cap is indeed a cheap and easy test.
even if it doesn't fix the issue, it's probably time to replace it anyway.