Over heating civic

Have a 98 Civic that is over heating. Changed thermostat, new radiator, antifreeze and it still over heats. I’m not sure what to do next. Any ideas will be greatly appreciated.

When the engine is cold, remove the radiator cap and start the engine.

While the engine idles, watch the coolant in the radiator.

If bubbles begin to form in the coolant, that’s an indication of a leaking head gasket.



We’ve done that and no bubbles.

Your new thermostat could be defective.Did you get one from Honda?

Make sure the electric fan runs.

Does it overheat in traffic? Or running down the highway? AC on or off?

Don’t bother getting a Honda thermostat. Honda doesn’t make thermostats. Stant supplies Honda with their thermostats.



A Honda this age frequently has a head gasket leak and over heating / losing coolant is a classic symptom. The engine is solid otherwise, if fixed soon enough you can get a lot more life out of it. Have your mechanic check it out.


  • Bad Water pump
  • New thermostat is faulty
  • Cooling system isn’t holding pressure (faulty radiator cap, small leak, etc.)

Ask your shop to replace the radiator cap, and if that doesn’t fix it, do a cooling system pressure test.

Can you be a bit more specific here… You replaced quite a few parts…how and why did you come to need these components and what was the back story while you were replacing them?

Walk me through the symptoms please. How severe of an overheat are we discussing? How many times did it overheat? Do your cooling fans function? Does your A/C cooling fan turn on when you select A/C? What is your idle quality like? Does it idle at the normal speed steadily? Or does it “hunt” for its idle speed?

In light of not having this information, I feel I need to warn you that this vehicle needs to have ALL of the air purged out of the cooling system for it to function properly. I do not believe you have a bleed nipple on this vehicle either…to tell you the truth, I honestly forget if it does or does not have one. Look near the T stat housing for a bleed nipple and use it if so equipped. If not equipped with a bleeder you will need several hot and cold cycles to try and purge all the air out of the system. Fill the rad as much as you can put the rad cap on properly so it seals (hopefully it can seal)…fill the overflow at least halfway…start engine and let it get hot. Then shut her down and let it get cold…this takes many hours… do the entire procedure again…and one last time… By the third go around you should have purged any air in the system.

Not to long after I got the car It over heated we found no coolant in radiator. Replaced radiator cap.
Was still getting hot found water pump was bad and leaking. Replaced that. The mechanic has been helping with the process of elimination.

Still getting hot replaced thermostat and radiator cap. Flushed out radiator and water was clean and fans are working.

Still over heating and losing coolant. replaced radiator.

Still over heating and losing coolant. There is no sign of a leak that we can see. Idling rough when stopped RPM is around 300-500. Acts like it’s going to die.

My son thinks it’s a cracked head.

I guess that’s next on the list to change.

Went back to AutoZone today because the check engine light came on. The codes show misfire on 1&2 cylinders and a random misfire. The last time we went to AutoZone codes showed misfire on all four cylinders.

Mechanic said it could be a cracked head or block. The oil looks normal not milky.

I’m open to any suggestions you may have.

Thank you,


Mechanic didn’t have one to fit to pressure test. Waiting for him to get it in

Previous owner took relay fuse out and has a wire from one side of the other.

The fan has been wired to run all the time.
It gets hot no matter what. In traffic and just idlein

Given what you say above, a little coolant might be leaking into the cylinders. That could put the spark out and cause the poor idle performance and misfires. The most likely paths would be

  • incontinent head or intake manifold gasket (considerably more likely than the second two)
  • cracked head
  • cracked block

A cooling system pressure test is a step in the right direction of determining if that’s happening or not.

Checked plugs and didn’t show signs of leaking in cylinders. Will be changing them this weekend

That’s good news. That’s a good test. When coolant leaks into a cylinder it can sort of appear like the spark plug has been steam cleaned. This leaves the uncomfortable question however: where is the coolant going? It’s not going into the oil, and not into the cylinders, and not dripping on the ground. Yet it is disappearing. A mystery remains.

Yes it does and it’s driving me nuts
Someone said it may be the block