I bought a civic from a couple of girls who had previously said that they had a bit of trouble with the car overheating, but it never broke down on them. It had 120k miles on it and they were asking 2k, my mechanic noticed a leak from the radiator and assumed that was the cause of the overheating, so I bought it for 1800 and went to replacing the cooling system.

The coolant was very gunky in the reservoir and the engine, so we flushed it out, we replaced everything but the water pump, and it started overheating again. The people we bought it from had a piece of copper in the temp sensor so the fan was always running, and when we checked the thermostat the day after the fail safe was triggered and the valve was wide open.

It wasn't losing any coolant, asides from when we bled it, and there was still air coming out after many attempts to bleed it and it was never a constant stream. I'm looking for some advice on what could be going on here, any replies will be greatly appreciated.

  • You say that the whole cooling system sans water pump was replaced. Did this include thermostat, radiator and hoses?
    – Zaid
    Mar 5, 2016 at 7:52
  • Yes, i should've specified, the hoses thermastat and radiator were replaced
    – Connor
    Mar 5, 2016 at 7:54

1 Answer 1


At a guess? From your description I'd bet it has a blown head gasket. The only way to tell if this is so is to do a sniffer test (search for "block tester") at the radiator. There are testers which, when in contact with hydrocarbons, change color from blue to green to yellow. Here is an example:

enter image description here

The only way the fluid will change color is in the presence of hydrocarbons (like I said), so if it changes at all, you know there is an issue.

  • Will there be hydrocarbins if i have a crack in my head/block or if it is warped?
    – Connor
    Mar 6, 2016 at 0:37
  • @Connor - The only way there would be hydrocarbons present is if exhaust were getting into your coolant system. If it is, you'll find nothing good. It will be a blown head gasket or a cracked block. More likely the head gasket, but it isn't a good thing either way. Mar 6, 2016 at 4:58
  • Good answer, but not exactly the only way to tell. You can also pressurize the cylinder side of the engine with a cylinder leak-down tester, described here. mechanics.stackexchange.com/questions/26384/…
    – kmarsh
    Mar 7, 2016 at 20:20
  • @kmarsh - A leak down will show you there is a leak. It won't tell you where that leak is occurring. You'd still have to confirm where the leak is coming from. While the compression test will confirm you'd need to take a head off, it won't tell you exactly what's wrong with it. From the description from the OP, this will be the fastest, surest way of discovering if it is the issue. Mar 7, 2016 at 21:26
  • 1
    @kmarsh - Gotcha. Misunderstood. Mar 8, 2016 at 17:36

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