car is a 1996 Honda Civic EK hatchback. B16A2 DOHC VTEC engine. Currently has 204,000 kilometres (127,000 miles)

When the car is on a stop and idling, the temp gauge needle goes up steadily, and when the car is running, the gauge goes back to normal just as fast. When the temp gauge is on hot and I rev the engine, temp gauge needle goes down a little bit. Fan switches on on Hot reading, then turns off when the needle goes down a bit, still the engine is not smoking nor does it feel really hot. It's just a normal temperature as far as I can tell.

Hood is warm, valve cover/rocker cover is hot but does not burn my hand when I touch it.

Overflow tank literally overfilled, I saw coolant stains around the overflow tank, on the fan shroud, and on the transmission case, then the next morning the overflow tank is empty probably due to the vacuum caused, hence the coolant inside the tank was sucked back in.

Thermostat was replaced with an OE replacement, but I do not trust this new thermostat, that is why I bought an OEM Honda thermostat. Still waiting to be installed.

Waterpump and timing belt, tensioner is also due for replacement.

Radiator was also replaced with an aluminium one, which is much thicker compared to OEM, however the coolant has not been replaced since it still looks good and I also bled the coolant for one hour. Although, the coolant still was bubbling after an hour of bleeding. When I rev the engine when bleeding, bubbles were present and at the same time coolant was boiling.

Hoses are old, but no signs of leaks. Coolant is not contaminated with oil, and oil on the dipstick and oil cap does look normal, no milky substance. Car does not blow white smoke. Hoses are both hot when fan switches on

When the car is running, and when A/C is turned off, windows closed, I can feel a little bit of heat coming out of the A/C vents (speed was about 60-80kph or approx. around 45 to 55mph)

Trusted mechanic said the engine sounds healthy but he did not perform any inspections, just a quick check since my car was not booked for servicing/repairs.

I will do all the servicing in one go as much as possible. Headgasket is also a suspect here but no compression tests have been done yet. No leaks except near the distributor and VTEC solenoid.

Anyone know what problems the cooling system have?

  • Does your heat work? Can you verify the fans turn on? Has the radiator cap been replaced? Are the hoses hard when the engine is hot?
    – rpmerf
    Commented Oct 19, 2016 at 12:51
  • Hi, the heater works but not that hot. It does the job. Radiator cap is brand new, it came with the new radiator. It's a 1.1 bar but I will get a 1.3 bar soon. Hoses are hard and both are really hot when engine is at optimal temperature.
    – 110100100
    Commented Oct 26, 2016 at 10:02
  • @110100100 I doubt this is still a problem being that this is almost a year old post, but it's also possible that you have exhaust leaking into the coolant lines. That will create a lot of fluid displacement and all you bubbling issues. If this has been resolved, you can select and answer, or answer your own question. That will prevent it from continuing to show up as unanswered. :) Commented Aug 30, 2017 at 0:14

2 Answers 2


There are two possibilities I can think of off the top of my head as I recently had a similar problem. One possibility is a partial or complete clogging of the radiator. Another possibillity is that the water pump is no longer functioning.

Both of these will lead to excessive coolant overflow due to lack of circulation causing hot spots to develop where the coolant is boiling and expanding to push coolant out of the system. This also creates air pockets which can make the temp gauge quickly jump or fall.

The first thing you should do is flush your cooling system. Prestone sells a nice flush kit for only a few dollars. You can get a spill free funnel to help ease the refilling afterwards.

If that doesn't help you may want to have the water pump checked. The impeller blades could have disintegrated after so many years.

  • Problem is I haven't used any of these flush kits before. Do you, by any chance, know any videos or instructions with photos?
    – 110100100
    Commented Oct 16, 2016 at 10:50
  • You can find on YouTube I think there is even a specific one for this kit but they're all pretty much the same. Commented Oct 16, 2016 at 11:12
  • I don't feel too comfortable cutting the hose, though. Is cutting the hose really necessary?
    – 110100100
    Commented Oct 16, 2016 at 11:54
  • Of course not! You can just go get a two inch piece of hose from an auto shop. Just disconnect the hose in stead of cutting it. The only thing is that some of these old hoses and connectors can be fragile, so when you are taking off one end of the hose go slowly and gently and don't use allot of force. I usually use a flat head screw driver and slowly go around the hose prying it off a little at a time. Commented Oct 16, 2016 at 15:00

If your engine cools while driving but overheats while stationary you either have too little to no coolant in the radiator or your fans don't work, or they are put on backwards.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .