Cylinder heads leaking coolant - 2009 Nissan Murano SL

No! Air bubbles in the radiator is usually caused by a damaged radiator hose, a leak in the radiator, a faulty water pump or there isn't enough coolant in the system. A blown head gasket usually leaks oil into the coolant and coolant into the oil. It may also run rougher if its leaking from cylinder to cylinder.

From what you have described you have radiator coolant leaking into the engine cylinders.

This will not be rectified by changing the gaskets on the rocker covers. That just stops engine oil leaking out from around the edges of the rocker covers.

The coolant will be leaking internally due to a failed cylinder head gasket and/or a crack in the cylinder head(s) and/or even a crack in the engine block. You will most likely also have combustion gasses leaking into the cooling system passages from one or more cylinders. I expect there will also be some coolant finding its way into the engine oil.

If you have allowed the radiator coolant to run low and hence for the engine to overheat at any stage that will cause the problems you have now.

You need to have tests run to check if you have a failed head gasket(s) and in that event the cylinder heads will need to be removed, the head gaskets replaced and, while removed, the heads checked for cracks, checked for any warping and overall condition. The engine block will also need to be checked.
If you run a compression test on all cylinders you will likely see the compression lower than spec in a number of them. A leak down test on each cylinder will show which cylinders have coolant leaking into them(and combustion gasses leaking out into the cooling system) and certainly confirm the need to remove the cylinder heads.

If you start the engine cold with the radiator cap removed, once the coolant has warmed and begins flowing from the engine via the top radiator hose to the radiator you will see bubbles in the coolant if there are combustion gasses leaking into the cooling system as described. This is an indication, (because the bubbles can also be air not properly bled out of the cooling system) but you still need to run a leak down test.

You need to have the problem checked out immediately as you do not want to be running the engine in this condition. Make sure you also check the level of the coolant in the cooling system and top it up when the engine is cool if not full. Coolant can escape quickly under normal cooling system pressure when the engine is running.

If you are losing coolant then you have either an external or internal leak.
If you can find no indication of an external leak from the radiator, the radiator overflow tank, any of the hoses on the system or around the water pump fitting then you may well have an internal leak. Check the radiator overflow tank carefully and the hoses to it for any signs of external leakage.

An internal leak of coolant can be via a failed cylinder head gasket or a crack in the cylinder head or both. Coolant can then leak under pressure into the cylinders or into the engine's lubrication system and will then mix with the oil. Check the condition and colour of your oil for evidence of coolant contamination. Check your exhaust for a constant flow of white exhaust emissions which is evidence of coolant entering the combustion chamber.

If you have run the vehicle with the engine overheating this will generally cause failure of the cylinder head gasket and possibly a crack in the cylinder head.

Usually white smoke from the exhaust means that there is radiator coolant leaking into one or more cylinders. Blue smoke is normally from burnt engine oil. Check your coolant level and you will probably find it is down below the full mark.

Have a leak down test done on all cylinders and this will show up a leak in the combustion chamber(s). You will also likely have combustion gasses leaking into the coolant passages and that can cause some overheating of the coolant. If you see bubbles in the coolant , once the engine has warmed up so the coolant begins flowing through the radiator, then you have a compression leak into the cooling system and in that event you will also have coolant escaping into a cylinder or cylinders and producing white smoke.

Coolant leaking into the cylinders will be via a blown head gasket or a crack in the cylinder head or both. If you have run the engine in an overheated condition this will certainly produce a damaged head gasket and possibly damage to the cylinder heads as well.

On the block ( the bottom part of the motor ) below the intake manifold

Loss of coolant is serious because if you allow your engine to overheat you can cause very expensive engine damage - thousands of dollars of damage (not hundreds).

The items that need looking at are:

- Radiator cap is old and faulty. This can allow coolant to escape and needs to be replaced every 4 or 5 years (sometimes sooner) with the correct spec cap - not any old product picked up at some auto store.

- External leak - you need to check all flexible coolant hoses and connections for leaks as well as around the water pump to ensure the WP gasket is not leaking

- Internal leak
The most common is a blown cylinder head gasket which can allow coolant to escape and to get into the cylinders and into the lubrication system. If getting into the cylinders you will see white smoke coming from the exhaust . You need to check the engine oil for coolant contamination as a coolant can escape into the lubrication system via a damaged head gasket. You also need to check the coolant for signs of oil escaping under pressure via the blown head gasket into the cooling system.

An internal leak can also be caused by a cracked cylinder head but if you have this condition are blown head gasket will have probably occurred around the same time.
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On an external head gasket leak you can see coolant leaking out between the cylinder head and engine block at the place where it is leaking .

An internal leak usually occurs into the cooling system . When this happens you might find that the cooling system will pressurize and you will experience coolant loss . The coolant loss may occur through the radiator over flow or on the other hand into the engine cylinders .

When this occurs through the engine cylinders you might find that the engine oil level will increase or the oil could turn a milky white color ( depending on the type of oil )

Also the exhaust smoke will be white in appearance as you rev the motor . ( caused by the coolant inhibitor being burnt in the engine cylinders )

You must have a intake manifold or head gasket problem, check to see if the oil level is high, if so it's most likely a intake gasket. Running a engine with this kind of problem won't last long.

WHERE COOLANT LEAKS OCCUR
Coolant leaks can occur anywhere in the cooling system. Nine out of ten times, coolant leaks are easy to find because the coolant can be seen dripping, spraying, seeping or bubbling from the leaky component. Open the hood and visually inspect the engine and cooling system for any sign of liquid leaking from the engine, radiator or hoses. The color of the coolant may be green, orange or yellow depending on the type of antifreeze in the system. The most common places where coolant may be leaking are:
Water pump -- A bad shaft seal will allow coolant to dribble out of the vent hole just under the water pump pulley shaft. If the water pump is a two-piece unit with a backing plate, the gasket between the housing and back cover may be leaking. The gasket or o-ring that seals the pump to the engine front cover on cover-mounted water pumps can also leak coolant. Look for stains, discoloration or liquid coolant on the outside of the water pump or engine.

Radiator -- Radiators can develop leaks around upper or loser hose connections as a result of vibration. The seams where the core is mated to the end tanks is another place where leaks frequently develop, especially on aluminum radiators with plastic end tanks. On copper/brass radiators, leaks typically occur where the cooling tubes in the core are connected or soldered to the core headers. The core itself is also vulnerable to stone damage. Internal corrosion caused by old coolant that has never been changed can also eat through the metal in the radiator, causing it to leak.

Most cooling systems today are designed to operate at 8 to 14 psi. If the radiator can't hold pressure, your engine will overheat and lose coolant.

Hoses -- Cracks, pinholes or splits in a radiator hose or heater hose will leak coolant. A hose leak will usually send a stream of hot coolant spraying out of the hose. A corroded hose connection or a loose or damaged hose clamp may also allow coolant to leak from the end of a hose. Sometimes the leak may only occur once the hose gets hot and the pinhole or crack opens up.

Freeze plugs -- These are the casting plugs or expansion plugs in the sides of the engine block and/or cylinder head. The flat steel plugs corroded from the inside out, and may develop leaks that are hard to see because of the plug's location behind the exhaust manifold, engine mount or other engine accessories. On V6 and V8 blocks, the plugs are most easily inspected from underneath the vehicle.

Heater Core -- The heater core is located inside the heating ventilation and air conditioning (HVAC) unit under the dash. It is out of sight so you cannot see a leak directly. But if the heater core is leaking (or a hose connection to the heater core is leaking), coolant will be seeping out of the bottom of the HVAC unit and dripping on the floor inside the passenger compartment. Look for stains or wet spots on the bottom of the plastic HVAC case, or on the passenger side floor.

Intake Manifold gasket -- The gasket that seals the intake manifold to the cylinder heads may leak and allow coolant to enter the intake port, crankcase or dribble down the outside of the engine. Some engines such as General Motors 3.1L and 3.4L V6 engines as well as 4.3L, 5.0L and 5.7L V8s are notorious for leaky intake manifold gaskets. The intake manifold gaskets on these engines are plastic and often fail at 50,000 to 80,000 miles. Other troublesome applications include the intake manifold gaskets on Buick 3800 V6 and Ford 4.0L V6 engines.

INTERNAL COOLANT LEAKS
There are the worst kind of coolant leaks for two reasons. One is that they are impossible to see because they are hidden inside the engine. The other is that internal coolant leaks can be very expensive to repair.

Bad head gasket --Internal coolant leaks are most often due to a bad head gasket. The head gasket may leak coolant into a cylinder, or into the crankcase. Coolant leaks into the crankcase dilute the oil and can damage the bearings in your engine. A head gasket leaking coolant into a cylinder can foul the spark plug, and create a lot of white smoke in the exhaust. Adding sealer to the cooling system may plug the leak if it is not too bad, but eventually the head gasket will have to be replaced.

If you suspect a head gasket leak, have the cooling system pressure tested. If it fails to hold pressure, there is an internal leak. A "block tester" can also be used to diagnose a leaky head gasket. This device draws air from the cooling system into a chamber that contains a special blue colored leak detection liquid. Combustion gases will react with the liquid and cause it to change color from blue to green if the head gasket is leaking.

Head gasket failures are often the result of engine overheating (which may have occurred because of a coolant leak elsewhere in the cooling system, a bad thermostat, or an electric cooling fan not working). When the engine overheats, thermal expansion can crush and damage portions of the head gasket. This damaged areas may then start to leak combustion pressure and/or coolant.

Cracked Head or Block -- Internal coolant leaks can also occur if the cylinder head or engine block has a crack in a cooling jacket. A combustion chamber leak in the cylinder head or block will leak coolant into the cylinder. This dilutes the oil on the cylinder walls and can damage the piston and rings. If the coolant contains silicates (conventional green antifreeze), it can also foul the oxygen sensor and catalytic converter. If enough coolant leaks into the cylinder (as when the engine is sitting overnight), it may even hydro-lock the engine and prevent it from cranking when you try to start it. Internal leaks such as these can be diagnosed by pressure testing the cooling system or using a block checker.

A coolant leak into the crankcase is also bad news because it can damage the bearings. Coolant leaking into the crankcase will make the oil level on the dipstick appear to be higher than normal. The oil may also appear frothy, muddy or discolored because of the coolant contamination.

Leaky ATF oil cooler -- Internal coolant leakage can also occur in the automatic transmission fluid oil cooler inside the radiator. On most vehicles with automatic transmissions, ATF is routed through an oil cooler inside the radiator. If the tubing leaks, coolant can enter the transmission lines, contaminate the fluid and ruin the transmission. Red or brown drops of oil in the coolant would be a symptom of such a leak. Because the oil cooler is inside the radiator, the radiator must be replaced to eliminate the problem. The transmission fluid should also be changed.

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u have a blown head gasket here and a cylinder that is full of coolant, this locks the engine up.