Why is There Oil in the Coolant?

This article was originally published on UnderHoodService.com.

When you check the coolant in your and the fluid looks brownish or milky, it’s likely that the coolant is contaminated with engine oil, signaling potential cooling system issues.

The Main Symptom Of Oil In The Coolant

The most common visual symptom of a leak that has been going on for a while is a brown milky sludge in the coolant, a telltale sign of oil in coolant problems. In the early stages of a leak, there may just be an oily sheen on top of the coolant. If the owner has missed these symptoms, the car may have overheated, exacerbating automotive cooling system failure.

If the coolant is contaminated with oil, it will need to be flushed and replaced – it’s the only sure way to achieve coolant contamination repair. The root cause of the problem will also have to be repaired to prevent further cooling system issues. Here are the most common causes of oil in coolant:

A Blown Head Gasket

“If the head gasket is bad, several repairs may need to be done.”

When a head gasket fails, oil can leak into the cooling passages and then end up in the coolant. Among other blown head gasket symptoms, this results in the brown sludge that can be seen in the top of the radiator and the coolant reservoir. Oil with coolant in it can also leak into the combustion chamber. This will result in a white cloud of sweet-smelling exhaust, a key indicator of a blown head gasket repair need.

A blown head gasket can be verified with a compression test, a standard step in engine and cooling system diagnostics. If the head gasket is bad, several repairs may need to be done. Blown head gasket repair steps:

• The head gasket, of course, will need to be replaced to fix head gasket failure.
• The entire cooling system will need to be flushed to resolve coolant contamination repair.
• The radiator and water pump should be inspected for leaks or damage, both at the time of repair and going forward as part of the regular automotive cooling system maintenance. (Cold oil is thicker than water. Pushing cold oil through the radiator and water pump may damage them.)

A Failing Oil Cooler

“If the oil cooler leaks, the engine will still perform normally, making it critical to diagnose diesel engine problems accurately.”

Oil coolers are not very common in gasoline engine vehicles, but turbocharged engines usually have them. If the oil cooler leaks, the main symptom is oil in the coolant, a common engine oil cooler failure sign. This can cause many people to think that the head gasket is blown. However, a blown head gasket usually affects the engine’s performance, unlike an engine oil cooler leak. If the oil cooler leaks, the engine will still perform normally, making it critical to diagnose diesel engine problems accurately.

Fortunately for the customer, an engine oil cooler replacement is a much less expensive repair than a blown head gasket repair. The oil cooler and its gasket will need to be replaced, and the cooling system will need to be flushed and refilled to complete the engine oil cooler leak fix.

A Leaking Transmission Cooler

Many cars with an automatic transmission have a cooler for the transmission fluid. Often, the transmission cooler is part of the radiator. Cracks can develop between the radiator and the cooler that allow transmission fluid to get mixed into the coolant, causing transmission cooler leak issues. This causes the coolant to be pink and foamy looking, a distinct symptom of transmission fluid in coolant.

The bad news is that the coolant can make its way to the transmission. This can damage the transmission to the point where it needs to be replaced, requiring a costly transmission cooler leak fix.

High-Quality Cooling System Parts From GMB

GMB is an industry-leading manufacturer of OE and aftermarket automotive products since 1943. With decades of experience producing high-quality automotive fuel pumps and cooling system components, we have OE specification replacement parts for many makes and models. Check out our full range of OE-quality parts for cooling system repair:

• Timing Belt Kits for reliable engine performance
• Tensioners and Idler Bearings for smooth operation
• Fuel Pumps for consistent fuel delivery
• Water Pumps for effective cooling system maintenance

If you suspect an issue with your cooling system or water pump and need a quality replacement, check out our catalog or contact our tea