Internal leaks are worse for two reasons. Firstly, they cannot be seen because they are hidden inside the engine. Secondly, the internal leaks of the coolant can be very expensive in the repair.
The punched head is the cause of the internal leaks of the coolant, most often due to the poor laying of the head. Due to the laying of the head, a coolant leak in the cylinder, or to the crankcase is possible. The cooling liquid seeps into the crankcase, dilutes the oil and can lead to damage to the liners in the engine. Cooling fluid leak in the cylinder can pour spark plugs, and create a lot of white smoke in exhaust gases. Adding sealant for the cooling system can stop the leak if it was small, but ultimately the laying of the head should be replaced.
If you suspect a leakage of head laying, you need to experience the cooling system with pressure. If it does not keep pressure, there are internal leaks.
The heads of the head often burn out as a result of overheating of the engine (which, possibly, occurred due to coolant leakage in other places in the cooling system, poor thermostat, or an electric cooling fan does not work). When the engine overheats, thermal expansion can crush and damage the head laying. These damaged areas can then start flowing under the pressure of combustion and / or coolant.
Cylinder head cracks can lead to coolant leakage inside the engine.
Block head or cylinder block – the internal leak of the coolant can occur if the head of the cylinder block or cylinder block has a crack in the cooling shirt. Leakage in the combustion chamber in the cylinder head or in the block allows the coolant leak in the cylinder. This dilutes the oil on the walls of the cylinder and can lead to damage to the piston and rings. If the coolant contains silicates (ordinary green antifreeze), it can also disable oxygen sensor and a catalytic neutralizer. If a lot of coolant flows into the cylinders (for example, when the engine is drowned out at night), this may cause hydro-blocking the engine and not allow promoting, when trying to start it. Internal leaks like this can be diagnosed with a testing of the cooling system.
Carter leakage in the crankcase is also bad news, since it can lead to damage to liners. The cooling liquid seeps into the crankcase, thereby make the oil level on the probe higher than usual. Oil can foam, be dirty or faded from the chopping liquid.
Leaky tubes inside the radiator – the internal leak of the coolant can also occur inside the radiator on the line associated with an automatic gearbox. On most cars with an automatic gearbox, oil from the box circulates inside the radiator. If the tube flows, the coolant can get into the line, pollute and destroy the transmission oil. Red or brown droplets of oil in coolant is a symptom of such leaks. Because the oil radiator is inside the radiator, the radiator must be replaced to eliminate the problem. Transmission oil should also be replaced.