I gave a 2004 honda civic and it started to overheat. While I was driving the temp gauge would go into the red for a minute or two and drop back done to normal while it was in the red the heater would blow cold until it went back down to normal. We replaced the thermostat and it was fine for a day and then the second day it overheated really bad. It blew the tube off that goes from the radiator to the engine. We then flushed out the radiator and checked for leaks and the radiator is fine. Once again it was fine for a day then the second day it did the same thing. We did the tests to see if it is a blow head gasket and it passes those tests. Is it the water pump? Would love some answers I don't have a lot of money and can't afford to take it to a mechanic unless it can for sure be fixed. Thanks

When the temp does that, there are air pockets in it. If you followed the correct procedure to remove all the air, then there is mostly only one way air is getting in the system...head or head gasket...assuming you can't find any obvious leaks on the engine or under the car.

Be sure that you are following the correct bleeding procedure for that car. Bleed it and make sure it is full. Drive it around a little, let it cool off, and then check the level of coolant.

You say you did a head gasket test but what was the test you did?

Honda's are known to overheat when the air is not properly bled from the system.

Sorry not the hose to the engine the tubing from the radiator cap to the overflow.

I checked for coolant in the oil and also with the radiator cap off revved the engine to see if water would bubble or shout out and it didn't do that.

The problem could easily have happened by not filling the cooling system per the instructions in the Owner's Manual, which were developed to properly purge all air from the system. Now, I suspect the aluminum head is warped, the head gasket is blown, and the cylinder pressure is blowing coolant out the overflow tube. The head likely needs to be machined, valves inspected for damage, and a new head gasket installed. This is the logical time to replace the timing belt, timing belt tensioner, water pump, and A/C belt tensioner bearing. I would install a new radiator and refill with a 50/50 mixture of the recommended antifreeze and distilled water, in accordance with the Owner's Manual's instructions. If the job is professionally done, it could easily cost $3,000.

If you didn't warp the head when you REALLY overheated it... it will actually be a miracle.

You can have a blown head gasket really easy without spewing steam out the tailpipe or water and oil mixing.

A professional shop would test for the presence of hydrocarbons in the radiator. As txgreasemonkey says....this is not an easy or inexpensive job.

I've done it on a Honda.....Twice.