Skip the auto shop - Our mechanics make house calls

Q: Black coolant - no oil

asked by on

I drained the coolant in my car and replaced it with distilled water and some coolant flush. I went for a drive then drained that coolant again, it looked fine. still kind of pink/ red. I filled the cooling system back with distilled water and went for a drive again, came back and let the car cool. I drained that water and it came out black. There was no oil in it(I made sure that there wasn't) and it was just cloudy. The reason I know it isn't oil is because I put that water in a container for recycling and let it sit overnight, it has not separated and there is no sludge on the top. I filled the car back up with coolant to be safe and I have yet to see what color it is now. Do you have any Idea why it came out black? I also installed an aluminum water temperature adapter so maybe that has caused some rust. could it be that the distilled water has reacted with the hoses or aluminum in the car? In the manual, it says to not use water alone... Maybe that's why.

Hello. Black or cloudy coolant can be caused by excessive rust or corrosion, or contamination in the cooling system. If the cooling system hasn’t been flushed or serviced for a long time, it may take a few cycles of flushing to get all of the contaminants out. Black coolant can also be caused by worn hoses that have decomposed and have now begun to break apart and contaminate the cooling system. I would examine the condition of all the cooling hoses, removing them if possible, to also examine the internal condition of the hoses. If you need assistance, a certified mobile mechanic from YourMechanic can visit your home or office to inspect the problem and flush your cooling system.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
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.