Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Honda loses heat, then overheats

My 2003 Honda Civic has 109,000 miles. Started with problems this past summer. Air conditioning on, stops blowing cold air and then temperature gauge goes to HOT. Again in the winter. Heat is on, stops blowing warm air and immediately temp gauge goes to HOT. Have had it checked both for the air conditioning problem and heat problem. Garage: Flushed the cooling system. Head gasket checked. Four new thermometers. They cannot figure out what is wrong. Any guidance would be greatly appreciated.

Did you have the timing belt and water pump replaced yet? Sounds to me like a water pump failing, and you’re past due for a timing belt change.

When it overheats (don’t let it, if you can help it), do the fans come on?
You could have an air bubble in the system. Have you burped it?

If You Were To Check The Coolant Right Now (When It’s Cold) In The Radiator And Reservoir, Would The Radiator Be Full And Reservoir At " Full Cold ? "

Do that if you haven’t.

Next, try replacing the radiator cap or wherever/whatever the cooling system pressure cap is. Buy the genuine, exact part from the manufacturer.

" Four new thermometers. "
This must be four new thermostats, right ?

CAUTION ! Do not remove any caps when the engine is warm. Do it when the car is cold to avoid being burned.


The Garage Flushed the system and re-upped the coolant…right? THEY NEED TO PROPERLY BURP THE AIR OUT OF THE SYSTEM…there is a bleed nipple specifically for this purpose.

AND…if they did bleed it correctly…you are now describing a failing head gasket. Hondas HATE to be overheated

SO…Bleed the cooling system and then pay attention you need to FEEL your radiatior hoses…if they are COLD…AND PRESSURIZED…u have a bad head gasket. The overheating…did not visit you lightly…when you overheat a Honda…badly… they warp the cylinder head…and then…they overpressurize their cooling systems due to compression leaking into the coolant (from the pistons) this pushes coolant out into the overflow…creates an air pocket…and starts the whole nasty overheat syndrome over again.

You need to bleed the cooling system…then when the engine is started…pay attention to the overflow bottle and the hose pressure… If you have pressurized radiator hoses early in the engine running process…it means the head gasket has failed due to the overheating. You are …to me…describing textbook head gasket failure…methinks

If you give us more info…i can guide you further


Thank you for your replies to date. What more additional information are you looking for? This “syndrome” seems to happen only in extreme temperatures. When the weather is mild, for example 40-50 degrees, the heat works ok and the temperature gauge does not go hot. It shuts off when I am trying to heat the vehicle in weather under 32 degrees and snowing or when it is 80+ degrees and you need the air conditioning. I have also noticed that I have no heat or air blowing down in the "foot area."
My garage has assured me that they checked the head gasket and it is fine and that they have done what was necessary to flush and clear the cooling system. I don’t do my own repairs. And yes, blush, it is thermostat, not thermometer.

When you turn your AC or defrost on, do both fans in front of the radiator come on as well?

Well, it sounds like it would be the cooling fans, but surely someone has checked that.
RemcoW, isn’t it possible that the fans would run with the A/C on but fail to run otherwise?

You’re absolutely right. that’s entirely possible - like when the thermosensor fails, for instance. That’s why I asked whether the fans come on when it overheats in the first post.
Turning the AC switch on is a quick way to make sure the fans work properly as it tests the fans, wiring, relays, etc. If a car overheats and the fans aren’t on, turning the AC on may actually get it to stop overheating, if you’re driving slowly. At high speed, fans don’t do that much so there it won’t matter.

One would hope someone tested the fans but some mechanics are just way better than others: Some, like the ones that post here, listen/smell/look/feel/taste and draw a solid conclusion based on experience and common sense.
Others are hopelessly lost without their OBD2 tester.

@EllyEllis most FWD cars have 2 electric fans.

The condenser fan comes on with the AC engaged.
The radiator fan comes on as needed, once a certain temperature is reached. The radiator fan may have 2 speeds.

db4690 Many cars have just one fan. That one fan comes on with the A/C or when the engine reaches a certain temp.

@EllyEllis you are correct, but this particular car happens to have 2 electric fans.

The older Benzes had a mechanical fan (with a a clutch) and an auxiliary fan in front of the condenser. When the auxiliary fan wasn’t functioning correctly, it would often lead to the engine running significantly hotter than normal. It is extremely important that all of the fans work, that all of the fan speeds are working, and that the fans come on at the appropriate temperatures and under the correct conditions.

That’s true, but I believe his vehicle has two fans.

@thesamemountainbike you don’t actually expect anyone to sort through that mountain of data?

I looked on
They show 2 different fans
Radiator fan
Condenser fan
They look physically different and have different part numbers

I’m not responding to this thread anymore.

I’m sorry you feel that way Db.

@thesamemountainbike I’m just not responding to this thread anymore.
I’ll still respond to other threads.

no hard feelings

'nuff said