The coolant system in your car is a pressurized system. As you operate your car, the coolant in your radiator warms and expands and thus flows into the reservoir tank. When you car cools, the excess coolant will cool and return back to the radiator, typically leaving the reservoir tank 1/3 full. Coolant should not move from this enclosed system. If there is a problem in this system you may find that coolant leaks from the exhaust manifold. What does this mean?
It is possible that the coolant has worked its way through your system and you have now noticed it leaking from the exhaust manifold or the tail pipe. This is more than a cracked coolant reservoir or a hole in your radiator. This is indicative of a more serious and costly repair and it need to be addressed quickly. Here are some possibilities of what could be the root of your problem
Bad Head Gasket
This is not a good leak to discover that you have developed. The head gasket is an internal leak. They can be difficult to diagnose visually because it is contained in the engine itself and it will be quite costly to repair. What happens in this scenario is that the head gasket will leak coolant into the cylinder or the crank case. This will dilute the oil and damage your engine’s bearings. This can also foul the spark plugs. If this happens you will see white smoke coming from the exhaust.
You can do a temporary 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 need to replace the head gasket but you will be able to get by for a short while.
Cracked Head or Block
This is another internal leak. Similarly, this is not a good place to experience a leak. If there is a crack in the cooling jacket of the cylinder head or the engine block, you may leak 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 foul the oxygen sensor and the catalytic converter. This type of coolant contains silicates. If the coolant leak into the cylinder is severe, you can end up locking the engine.
Again, this is yet another bad internal leak. You may have a coolant leak into the crankcase. The oil level, as measured by the dipstick, will appear higher than it normally is and it may also appear frothy or oddly colored. This type of leak can damage the bearings.
Intake Manifold Gasket
This is the least serious of the problems 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.
Knowing what is causing the coolant to leak from your exhaust manifold can help save you time and money. Just remember to consult a mechanic if you find yourself in over your head.