Can Water Get in Oil From a Blown Intake Gasket?

On the V-type engines, intake manifolds are made of cast aluminum, iron and, in some cases, plastic. They sit directly mid-engine between the heads. The manifold has two angled mating surfaces, one for each head bank. Large bolts must be properly torqued to specifications to connect and seal the intake manifold to the cylinder head. The intake manifold gasket has rear and front water passages, joining the manifold with the head, to allow coolant to flow and cool the cylinder head, as well as large fuel port openings and bolt holes.

A blown intake manifold gasket shows itself by the condition of the engine oil when checked with a dip stick. If the vehicle has an oil leak, the oil will also appear altered in color and texture. Water-contaminated oil will look light brown and exhibit a frothy or creamy texture the consistency of a milkshake. The frothy texture results from churning and air in the oil. Oil will not necessarily enter the cooling system with a blown intake manifold gasket.

Intake manifold gaskets are designed to crush upon the torque applied to them between the head and manifold, forming a seal. Temperature fluctuations during constant engine heating and cooling can warp the manifold contact surface and allow gasket leakage. Age can cause the eventual deterioration of the gasket material, allowing a split or break. Severe engine overheating can warp the manifold or head, causing leakage as well as burning the gasket material. Corrosion and rust in a water passage can weaken and disintegrate gasket material.

Engines that have a one-piece manifold-to-head seal without a lifter valley cover will leak on the inner edge of the gasket close to the coolant passage. Coolant will bypass the gasket seal and leak down into the lifter valley. The coolant will proceed to drop into the oil pan and collect there. Some model vehicles do not have such a passage, or have the lifter valley sealed off by a separate cover.

When the intake manifold gasket breaks and allows coolant to mix with the engine oil, the oil becomes diluted and loses its viscosity. Depending upon the severity of the leak, the engine might run hot. The radiator or overflow coolant reservoir level will drop noticeably. Water-contaminated oil will raise the engine temperature through increased friction. Connecting rods, crankshaft bearings, camshaft bearings, valve train rockers and shafts, valve stems and other major metal components will begin to fail. Water-contaminated oil leads to eventual seizing, galling and breakage of major engine components.