Overheating 1996 Honda Civic

Question

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.

I've...

• 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?

Answer 1

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.

Answer 2

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:

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.