The coolant system in your vehicle is a pressurized system. As you use your car, the coolant in your radiator warms and expands thus flowing into the reservoir tank. When the car cools, the excess coolant will cool and return to the radiator, typically leaving the reservoir tank 1/3 full. Coolant should not escape from this enclosed system. If there is a problem in this system however, you may notice that coolant leaks from the exhaust manifold. What does this indicate?
It is possible that the coolant has worked its way around your system and you have now noticed it leaking from the exhaust manifold or the tail pipe. This is something more than a cracked coolant reservoir or a hole in your radiator. This is a sign of a more serious and costly repair that needs to be addressed quickly. Here are some examples of what could be the cause of your problem
BAD OR WORN HEAD GASKET
This is not a good leak to notice that you have developed. The head gasket is an internal leak. They can be trying to diagnose visually because it is found in the engine itself and it will be quite a costly repair. What happens in this situation is that the head gasket will leak coolant into the cylinder and or the crank case. This will dilute the oil and spoil your engine’s bearings. This can also spoil the spark plugs. If this occurs you will notice white smoke issuing from the exhaust.
You can however carry out a remedial fix on type of leak by adding a sealer into the cooling system. It may seal the leak if it is not extensive. You will still be required to replace the head gasket but you will be able to operate the car for a short while.
CRACKED HEAD OR BLOCK
This could create another internal leak. Similarly, this is not a good environment to experience a leak. If there is a crack in the cooling jacket of the cylinder head or the engine block, you may notice leaked coolant into the cylinder. This is damaging to the engine because it will dilute the oil on the cylinder walls, thus damaging the piston and rings.
If you use traditional green antifreeze you can also spoil the oxygen sensor and the catalytic converter. This type of coolant has silicates. If the coolant leak into the cylinder is severe, you can wind up locking the engine.
Still, this is another bad internal leak. You may have a coolant leak into the crankcase. The oil level, as shown by the dipstick, will read higher than it normally is and it may also appear frothy or oddly colored. This type of leak can cause damage to the bearings.
INTAKE MANIFOLD GASKET
This is the least serious of the problems to be addressed. The intake manifold gasket seals the intake manifold to the cylinder heads. It may leak and allow the coolant to enter the intake port, the crank case, or it can drip down the side of engine on the outside.