2004 Honda Civic overheating

2004 Honda Civic ex, Over heating, " Disappearance of coolant" Hi, I have a 2004 Honda Civic ex coupe. I have changed the thermostat (twice), fan sensor, temp. sensor. The fan works and when doing an oil change the oil looks normal. No white smoke coming out of my exhaust and I got two radiator flushes, no dirty coolant, and I have replaced the cabin filter. The car doesn’t overheat as long as I keep my temperature on hot. If I were to change the temp. to cold it seems like the coolant goes into the reservoir, but it seems like it doesn’t go back into the engine. The mechanic that did the flush said that the hoses doesn’t to be clogged because the coolant that was removed was green. They stuck an air blower in the heater core hoses and to show that was not clogged as well. Any help would help, i Thank you P.S. the AC worked, I haven’t checked in about couple of months. Also when the car overheats there is no smoke coming from the engine. radiator has been burped as well.

If coolant is disappearing, it’s probably due to a leaking head gasket, which causes the overheating. Lack of white smoke does not necessarily mean the head gasket is OK. It just means the leak is small enough not to cause visible smoke.

+1 to jesmed, this vintage Civic is noted for leaking head gaskets. When you get the head gasket worked on might as well get the timing belt/water pump replaced. Probably time for these. If you get this done your car will probably be good to go for another 5 years with out much trouble.

I had the timing belt and water pump replaced as well, it doesn’t overheat until i use the ac or change the temp. to cold. the temp is on hot but the heater isn’t on and the car never overheats, coolant is never low. but when i change the temp. gauge to cold it gives me problems. the first time i got my timing belt changed the i drove it for about 1k miles and the belt fell off. no damage, i dont think, to the engine because i driving it. but i replaced the belt and drove off, obviously it was timed by the mechanic. I would really hate that i would need to get the head gaseket replaced. 190,000 on the car. thank you guys for the very quick response.

I bought my '04 Civic EX new. Your comment about " it seems like the coolant goes into the reservoir, but it seems like it doesn’t go back into the engine." is what mine was doing with a blown head gasket in Aug 2010 at 122800 miles. After the repair, the car is at 185k with no further problems.

Thanks Guys, any ideas on how long and how much it would cost?

Somewhere just over $1000, perhaps $1200, is typical. And it sure sounds to me too like you may have a blown head gasket. One of the characteristics of a blown head gasket is the fluid not returning to the engine when the engine cools. Normally as the engine cools and the coolant contracts, it draws the coolant up from the reservoir like milk up a drinking straw. But of there exists a path between the water jacket and a cylinder, it will draw air into the water jacket through that headgasket breech instead. 50% of the time you’ll have a valve open in an given cylinder, so there’s plenty of opportunity for the engine to stop with a valve open and provide an excellent opportunity for the contracting coolant to draw air in instead of drawing coolant from the reservoir.

But before considering this, be sure it’s properly diagnosed. There are a number of ways to do this, some you can do safely at home. There is an inexpensive “lab kit” that can test the coolant for the presence of combustion byproducts. If you have a headgasket leak they’ll be getting blown into the coolant. Additionally, if with the radiator cap off and the engine running, bubbles are coming out the radiator fill hole, that is a good sign that you have a blown head gasket. There’s also a “pressure leakdown test” that you can do at home if you’ve a bit of mechanical aptitude(the kit will provide instructions).

I had the same issue with an '03 Civic EX - coolant not being pulled back into the motor from the coolant tank. I tried everything, but eventually bit the bullet and had the head gasket replaced. End of problem. The car has just under 160K miles on it. My job was about $1,100 and the shop changed the timing belt so I can go another 100K before needing that job done again.

Your head gasket breach is allowing some exhaust gases to get pushed into the coolant. This increases the pressure in the cooling system and pushes the coolant out into the coolant tank, and creates a gas/air gap so the coolant isn’t sucked back into the engine when it cools off. The level of the coolant tank then stays steady so it might appear you aren’t losing coolant. If you pop the radiator cap (when the motor is cool) you will see it is “dry” under the cap and in my case there was a release of pressure (a distinct swoosh sound) every time I’d take off the radiator cap.

I’m 99% certain the OP’s problems are due to a leaky head gasket.

Machining the gasket face on the cylinder head might add $300 or so to the costs given. The shop will not know this until the head is removed. If the face of the head is not flat within a very close tolerance when reassembled, the new gasket will not be able to seal for the long term.

Have you replaced the radiator cap?
If it doesn’t hold proper pressure you can get steam bubbles that play havoc.

I haven’t replaced the radiator cap. when i am driving i hear a swooshing sound, Uncle Turbo, you’ve just described my car, thanks a bunch guys. I guess i should start looking for another motor, brother is a mechanic fortunately.


Ask your mechanic to perform a block test

If he doesn’t know what that is, he’s probably not the guy for you

This is a block tester


If he claims the car doesn’t have the symptoms of a blown head gasket, say “Fine, but can you perform the block test anyways, just to rule it out?”

If he then refuses to do it, take your car elsewhere for a proper diagnosis

How about the radiator? Has it been replaced? Engine is using the heater core as a radiator that is why there is no overheating when controls are in “hot”. There is nothing cooling the engine coolant when the controls are in “cold”

I would not go into panic mode yet about engine problems. It could be that the answer is simpler and far less expensive.

You state that the radiator has been flushed. Sometimes that will not cure a badly clogged radiator.

Overheating can also be caused by a partially clogged catalytic converter or a worn engine that is having to struggle a bit even if none of this is very noticeable to the driver.

Is there a pattern to the overheating? Does it overheat at idle, mixed driving, only on the highway, etc, etc?

Did this problem surface right after the timing belt job?

Hey… My car does seems to do a similar thing but could a blown head gasket cause the car to crank and not turn on sometimes or to turn on immediately othe times??