In most cases is is blown head gasket. The engine suckes air through the hole in the gasket and sends it to cooling system. You never know how long it gonna last.
Can also be caused by a defective pressure relief valve in the coolant reservoir cap. If it is the head gasket, you may also find you can smell combustion gases in the coolant. These won't smell the same as the exhaust gas though as the exhaust has been through the catalytic converter. If changing the cap fails to cure the problem, disconnect and isolate the ht leads or coil low tension wires and remove the pressure cap from the coolant tank. Get someone to turn the engine over on the starter motor while you look into the tank. If you see bubbles emerging in the coolant, it's probably the head gasket.
And a worse case scenario, a cracked head is possible.
Normal causes are low coolant and an inoperative radiator fan.Normal causes are low coolant and an inoperative radiator fan.
Don't! Most cars have a reservoir for radiator coolant ... add liquid to the reservoir. Opening the radiator cap introduces air into the sealed system ... you don't want air bubbles in the cooling system.
Indicates a bad head gasket or a cracked head.
Find out where you're leaking. Anything that causes the coolant to leak out is cause for concern. Fill the radiator. Leave the radiator cap off and start the engine. Watch for bubbles. If there are quite a few bubbles and the coolant wants to blow out even before the engine gets warm, you might have a head gasket problem.
Defective radiator caps or tubes
If your exhaust is getting in your coolant, you have a reeeeeeeeeeeeaaaaaaaaaaaaaaaaallllllllllllllllllyyyyyyyyyyyy major malfunction.
Check to coolant level in the coolant recovery tank and radiator when engine is cold
Possible trany cooler leak
Lack of coolant, lack of coolant flow, air in cooling system, lack of airflow over radiator,........
Loss of coolant with no visible leak. White smoke out the exhaust. Excess pressure and bubbles in radiator.
If you have coolant mixed with air bubbles coming out, you may have a cracked head or a bad head gasket. Have a pressure test done on the cooling system to verify there is a problem.
Let it settle. You maybe fooled about the bubbles if your are checking it while the fluid is hot. At rest with the engine cooled down, there wouldn't be any bubbles. Check the coolant level when engine is cooled off and not running.
Broken or split hose Radiator leak heater core leak
I had this problem ....Head Gasket or radiator cap
Lack of coolant, faulty thermostat, radiator fan not working...
Head gasket? Low coolant level? Water pump not circulating coolant? Thermostat not opening? Radiator plugged or restricted?
Coolant goes in the radiator or you can also fill the radiator resevoir.
In systems that do not have a radiator cap, the coolant is drained by the radiator drain plug. It is filled by adding coolant to the system through the overflow bottle.
Could be, Restricted air flow through outside of radiator, Restricted coolant flow through inside of radiator, Faulty fan clutch, Missing or broken radiator fan shroud, Faulty thermostat, Low on coolant,
The radiator cap could be the cause of coolant reservoir overflow or backup. Have the cap checked to see if it is bad.
It could be a number of things, a clogged radiator,bad thermostat,low coolant, hoses leaking coolant, radiator fan not working,or a leaking head gasket. Hope this helps you.
Low coolant, radiator restriction.Low coolant, radiator restriction.
If the bubbles are because you need to bleed the system, full bleeding can have many sequences. All cars require that your heater is set to the max heat so that the valve is fully open and able to except coolant and allow to release bubbles. you'll also have to fill the radiator with the correct coolant all the way to the filler neck. next you'll have to see if your vehicle has a bleed valve somewhere around the engines upper inlet. if it does have one open it slightly. bubbles will Begin to escape as the are escaping keep filling the radiator to the top till you see that threw the bleed valve your getting a steady stream of coolant coming out. If it does not have a bleed valve you will have to fill it to the top. Turn the engine on and allow the thermostat to open. when this happens the coolant level will drop. Add more coolant in the radiator and accelerate the vehicle to 2000 rpm for 2-3 minutes. this will allow the water pump to pull air bubbles out the radiator filler neck. you will have to do this maybe 3 times max to get all air bubbles out of the system. once you have achieved this fill the reservoir to the middle of the hot and cold lines because by then you have warmed up your engine a bit.
coolant draining back into resivoir or possible air pocket