My '96 Honda Civic is overheating. Either my head gasket is blown or my water pump is frozen.

It overheats when...

  • I start it and let it run in the driveway for 5 minutes.
  • I run it up and down the street by our house.

What I've Tried

Between each step, the car still overheated.


  • Checked coolant. (I used a 50/50 premix blend). Coolant is okay.
  • Checked/replaced thermostat.
  • Checked/replaced thermo switch.
  • Jumped power to fan: it runs when jumped.
  • Flushed/filled radiator.
  • Replaced radiator cap.
  • Replaced radiator.
  • Bled cooling system by the book.

Diagnostic Info

  • There is absolutely no milkiness on dipstick.

  • There is no evidence of mixing of coolant and oil visible when I pulled off the valve cover.

  • There is no leaking coolant on the ground.

  • There is no white vapor from the tailpipe.

  • There is no sweet odor from the tail pipe.

  • There is no moisture or puddling in the floorboard.

  • The lower radiator hose is soft and flexible and not at all hot to the touch.

I used a head gasket test kit from the auto parts store:

  • The first read was nearly an immediate color change from blue to green.

  • The second and third tests showed no color change at all.

  • It is possible that I mistakenly sucked some radiator fluid into the test chamber the first time.

Any ideas what this could be?

  • Is the radiator running cool? Has the temperature of the hose changed after changing the thermostat?
    – Martin
    Commented Aug 26, 2016 at 15:19
  • If the bottom radiator hose is cool to the touch, you have an issue with coolant flow. If you've changed the thermostat and there is no blockage in the radiator (new radiator), that about leaves an issue with the pump, I'd think. I doubt the water pump is frozen, though, as this would directly affect the timing belt. If the water pump is to blame, I'd think the impellers might be deteriorated. Commented Aug 26, 2016 at 16:02
  • "Jumped power to fan, it is running when jumped. Flushed/filled radiator." does it run when it is supposed to?
    – Moab
    Commented Aug 26, 2016 at 21:08

2 Answers 2


Here are the symptoms I would expect for a bad water pump:
No heat inside the car
Radiator and coolant hoses cool to touch.

No heat inside the car is usually a pretty good indication, but no heat could also come from a bad heater core or heater core valve.

A cool radiator and hoses means coolant is not flowing through the radiator. This is either a bad thermostat or a bad water pump

I've had a water pump fail where the impeller was plastic and not spinning with the pulley.


I experienced almost this exact problem with my Mazda 626. Coolant was boiling out the overflow bottle, yet my lower radiator hose was cool. I also had no circulation to my heater core ( both hoses were coolish / warmish and I was getting at best luckwarm air ). I back flushed my radiator and heater core, and had recently replaced my thermostat.

So I removed the thermostat and stuck an endoscope into my water pump to get some video and discovered that all the fins on my water pump impeller had completely disintegrated:

enter image description here

You can grab an endoscope off amazon pretty cheap and verify for yourself the integrity of your impeller fins visually before you go pulling stuff apart.

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