What Causes White Foam in the Radiator?

[AllisonMarie]

Specific reasons are as follows: 1. Damaged Cylinder Head Gasket: The water pipe and oil passage are connected, causing the coolant and engine oil to mix on the engine block. The coolant, now contaminated with oil, changes color. Under the pressure of the cylinder, it enters the water passage, resulting in white foam during the coolant circulation. Large amounts of thick foam in the coolant may also be caused by this issue. 2. Air Bubbles During Startup: Air bubbles appearing during startup may be due to air trapped in the coolant. As the coolant circulates, the air is expelled, which is a normal phenomenon. 3. After Air is Expelled: Check the coolant level. If it is below the "min" mark, add coolant to bring it within the normal range. When adding coolant, wait for the engine to cool down to avoid the risk of coolant spraying out.

[Haymitch]

I've encountered the issue of white foam in the radiator several times. The main cause is usually a blown cylinder head gasket, allowing combustion gases from the engine to enter the cooling system. When these gases mix with water, they create white foam. Another possibility is excessive air in the coolant or incorrect water-to-coolant ratio - using hard tap water can easily cause this. Last time my friend's car had this problem, we found the water pump seal was broken and letting in water, which affected the entire cooling system, causing the temperature to skyrocket and severe bubbling. I recommend immediately checking the head gasket and replenishing coolant - don't delay as it can damage the engine. For regular maintenance, use dedicated antifreeze and avoid mixing in impurities to prevent such issues. Safety first.

[StMadelyn]

My car once had white foam coming out too, which I noticed on the highway. It scared me so much that I immediately pulled over. There are many reasons for bubbles in the radiator, with a head gasket issue being a common one, but air entering the cooling system is also not uncommon—like if you recently changed the coolant and didn’t properly bleed the air before driving off. Additionally, degraded coolant or adding unclean water with an incorrect mixture ratio can also cause foaming. When I took it in for repairs, the mechanic said it was due to an aging head gasket, and replacing it fixed the issue. I’d advise you not to overlook regular maintenance; at least check the cooling system annually to ensure safer driving and avoid last-minute panic like I experienced.

[OLyla]

White foam in the radiator is mostly caused by a damaged cylinder head gasket or air entering the cooling system, where gas mixes with water and bubbles form. Poor-quality coolant can also cause this, as uneven mixing leads to foaming. It's best not to take it lightly and to get it repaired promptly to avoid minor issues escalating and affecting driving.