1. Check your coolant level. Look for a "full" line or "max" mark on your coolant reservoir. If the level is low, add more coolant according to the recommendation in your owner's manual.
2. Inspect your radiator cap. Make sure it's tightly sealed and not damaged. If the cap is loose or damaged, replace it.
3. Bleed the air from your cooling system. This process helps to remove any trapped air from the system, which can cause brown foam. Instructions on how to bleed the air from your cooling system can be found in your owner's manual.
4. Check your thermostat. If the thermostat is faulty or stuck shut, it can cause your engine to overheat, which can cause the coolant to foam. Test your thermostat by placing it in a boiling water bath and verifying if it fully opens.
5. Inspect your water pump. If the water pump is not circulating the coolant properly, it can cause overheating and foaming. You should inspect the water pump for any damage or leaks. If needed, replace it with a new water pump.
6. Check for leaks. Look under your car for any visible leaks. Inspect your radiator, water pump, hoses, and the area around the cylinder head. If you find a leak, repair or replace the faulty component.
7. Consider a head gasket issue. A faulty head gasket can allow exhaust gasses to leak into the coolant system, which can cause the coolant to foam. If you suspect a head gasket issue, have your car inspected by a qualified mechanic or technician.
8. Check if you added the wrong coolant. Using the wrong coolant or mixing inappropriate types of coolants can cause foaming and other issues in your cooling system. Verify the type of coolant specified in your owner's manual and ensure you've added the recommended type of coolant.
If you've checked these things and the brown foam persists or becomes worse, it's recommended to take your car to a qualified mechanic for further diagnosis and repair.
