Constant coolant loss, engine overheating, foam in radiator cap, and overflow tank getting full.

[civic_fd]

Car: Honda Civic FD4

Problem: Engine overheating at long distance journeys and loss of coolant (about 500ml per 30 minutes drive). 

Observations: 

1. Foam creating in the radiator cap (currently running with only water due to coolant loss). 
2. Overflow tank getting full all the time after a drive. There are some foam in the overflow tank too. 
3. Occasional white smoke during the morning, cold starts. 
4. A leak in the radiator core. 
5. The mechanic said it takes a longer than usual time for the thermostat valve to be opened. 
6. Both fans work without A/C but takes time to turn on. 
7. No other visible external locations for coolant leakage. 

Things Done:

1. Replaced the radiator.

Question:

What could be the reason? If it's a blown head gasket (or something else), what is the correct procedure to diagnose/fix it? 

[varotone]

Start by filling the overflow bottle to the correct level when the engine is cold. Start by checking for visible leaks. Radiator core, tanks, overflow tank, coolant lines when the engine is warmed up to operating temperature and thermostat is open.

Is there oil in the radiator? Is the radiator cap good? Correct specs? Loss of compression? Water in the engine oil sump?

 

A bit of foam is normally created due to the circulation of coolant. Excessive frothing or bubbling with oil can be due to a blown head gasket. It will also make a lot of white smoke. Steam to be more specific.

[civic_fd]

On 1/18/2021 at 5:01 PM, varotone said:

Start by filling the overflow bottle to the correct level when the engine is cold. Start by checking for visible leaks. Radiator core, tanks, overflow tank, coolant lines when the engine is warmed up to operating temperature and thermostat is open.

Is there oil in the radiator? Is the radiator cap good? Correct specs? Loss of compression? Water in the engine oil sump?

 

A bit of foam is normally created due to the circulation of coolant. Excessive frothing or bubbling with oil can be due to a blown head gasket. It will also make a lot of white smoke. Steam to be more specific.

Thanks. My mechanic has done a gasket replacement and now it seems ok.