Q: There is a small brown sludge oil layer in my coolant tank.

asked by on

I recently had my water pump changed. After a little while I noticed a thin brown sludge oily looking layer in my engine coolant reservoir. The bright red coolant is still in there and separated from the sludge layer.

My car has 100000 miles.
My car has an automatic transmission.

Often times, sludge in the radiator is an indicator of a leaking cylinder head gasket, which can lead to major engine damage if not checked out soon. A blown head gasket may cause a number of different symptoms. A head gasket that fails between cylinders will generally cause a misfire and potentially compression leaks from one cylinder into another. Low compression will eventually result in a rough idling engine. When the head gasket fails between a cylinder and the coolant port, coolant may leak into the cylinder causing it to be burnt with the fuel charge in the combustion chamber. This often results in misfires on startup, especially after the engine is run, turned off and restarted and in some cases may result in the engine not maintaining enough cylinder compression to even run or start. You may also notice a slight bit of steam like smoke being produced from the exhaust as a result of the coolant being burnt inside the combustion chamber along with the fuel charge. This type of failure may not always show with a compression test. I would recommend having an expert from YourMechanic come to your location to properly diagnose the symptoms you describe.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. There is a small brown sludge oil layer in my coolant tank.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: What does the oil life feature do?

Your car’s message center lets you access a lot of information about the various systems on your car and their condition or status, including the remaining oil life. Press the Reset button to cycle through your options until you see...

Q: Q: Car shaking

Vibration at idle is due to either failed motor/transmission mounts or an engine operating condition that causes a rough idle. If you are getting vibration through the steering wheel at speed, the most common cause is a wheel/tire imbalance although...

Q: Q: Headlight not working

Hi there. A head light replacement sounds like an easy task but can commonly be done incorrectly. If care was not taken by the technician that installed the headlight and the light was handled by the glass part it will...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.