Coolant way above max fill line

hi – my car overheated the other day. i noticed later that the coolant tank contained thick-looking coolant way above the max fill line. i checked it again this afternoon (car was sitting for 24 hours); same max-fill problem. just now, i drove my car around a bit, it didn’t overheat, but when i checked it afterward, same problem. help!

Make, model, year, and mileage please.
And any other info you can add.
Such as what did you do when the car overheated? What were the conditions of the coolant at that time? Any other problems or symptoms lately?

sorry, should’ve been more specific – 2000 honda civic hatchback, 98K miles. overheated on a sunny winter day (about 40 degrees out), after driving around christmas shopping. the car was overheating just as i got home (luckily!). i didn’t look under the hood at that time.

Any idea what caused the “thick looking coolant”? We normally see this when someone had a coolant leak and added a large amount of “stop leak” or whatever is sold for that. You could have a stuck thermostat or your coolant is so thick, it expands into the overflow tank and does no siphon back. In which case your coolant in the radiator might be too low.

In any case, check the coolant level in the radiator; the other cap mounted on the rad. Do it with the engine cold. If the level is high enough, then a good shop should test for a bad thermostat or a worn water pump. A cooling sytem pressure test is also in order. DON’T DRIVE THE CAR WHILE HOT!! That can cause very expensive damage.

Good luck!