Honda civic overheating no apparent reasons, confusion

I own an 03 Civic ES with a manual trans. You are experiencing classic symptoms of a civic failed head gasket. Mine was replaced at 155k miles and had all the symptoms. At 163k now it is back to it’s normal bulletproof self.

@UncleTurbo But how when it’s failing the hydrocarbon test and no signs of it other than overheating?

The breach is very small, but enough to push fluid into the overflow tank, and when the block cools there is no vacuum created to pull the fluid back into the block. Perhaps it should fail a hydrocarbon test but the test process was faulty and gave a false result.

Don’t waste more money, your head gasket is the problem. At 150k miles they all go bad or soon will.

“Perhaps it should fail a hydrocarbon test but the test process was faulty and gave a false result.” could you elaborate on that more.

I go through about a gal of coolant in 2 weeks or less. How could it be going through that amount of coolant and not appear as hydrocarbon, milky dipstick, pummels of smoke. I am not a car expert by any means here but something doesn’t make sense here. Why is a small breach or pinhole causing it to overheat? I don’t quite understand why a crack or hole somewhere on the head-gasket paneling would cause it to overheat in the first place. Excuse my ignorance, but does antifreeze go into the head gasket area at any point in the system. Or does the fact that it has a hole somewhere in the gasket cause things to heat up for some reason and thus exceeds the antifreeze temp max and forces it to shoot out the reservoir?

You’re losing coolant into the combustion chamber. If you had milky oil or plumes of white smoke you wouldn’t have a head gasket failure you would have a ruined engine.

You have all the classic symptoms of a head gasket failure. Maybe the gasket has slightly corroded over the years. Maybe a previous overheat years ago caused the torque-to-yield bolts to weaken ever so slightly that they now fail when they are fully warmed up, as when you drive for an hour. Maybe there’s a hairline crack in the head that only opens up after being at 220 degrees for an hour. At any rate with all the testing and checking you’ve done the next step is to remove the head and inspect.

@asemaster I take your opinion in high regard. Why is it that when people talk about a blown head gasket or just googling it always comes up with those same symptoms of: pummels of white smoke, milky dipstick if that isn’t a blown head gasket but a ruined engine. Also, my mechanic also recommended maybe getting a new thermostat, but I already had a new one installed about a year ago from the 2nd mechanic I went to. Besides I’ve heard that thermostats rarely go bad, bought it brand new from napa. He also said he couldn’t get it to overheat stationary, and that only when it overheats will they be able to identify the problem. Given the failure of the hydrocarbon test and pressure test.

Maybe I’m reading this wrong but did the OP say he was driving 60 miles in 45 minutes? That’s pretty fast with a little Civic, counting stops and starts, he’s really moving. But nevertheless, how about some of the cheap and easy stuff? Radiator cap? Thermostat? Binding brakes? Rocketman

@rocketman sorry it’s actually 30, idk where I got 60 haha.
Radiator, radiator cap, thermostat have all been checked. Not the brakes though. But everything seems to point to the head gasket being the culprit. Which I will take the advice of asemaster and get the head gasket inspected.

I’ve been driving Hondas for almost 30 years and can tell you that you’re probably right, a head gasket. Of course none of us on this forum can tell much from where we sit, but most times I’ve either experienced myself or with a friend overheating with a Honda it turns out to be a head gasket. The Honda doesn’t like to get overheated and will blow a head gasket pretty fast. Don’t bother with the liquid repairs, get your tech to pull the head and replace it. How’s the rest of the Civic? Rocketman

Replace the gasket, that is.

@rocketman can not really complain about anything else on the car. When I got it t was my first car and when it started to overheat I should have returned it, but I thought it would be an easy fix but low and behold this. All because I loved the rest of the car. The brakes need replacing now and timing belt soon. Recently blew a fuse 15 in the lighter. Everything else is great smooth ride, amazing fuel-economy nothing else has needed work.

There are a dozen different ways a head gasket can fail. By the time the engine oil is milky or there is steam coming out of the exhaust chances are the engine is too far gone to be repaired for long term reliability.

It would appear your head gasket has failed such that there is a breach between the cylinder compression ring and a coolant passage. Just letting an engine sit stationary and idle puts such a small load on the engine that more heat and strain is required for the failure to be apparent. I’m guessing that if your mechanic rode along with you for an hour and then performed the chemical block test or a combustion gases check using a gas analyzer on the side of the road while the engine was overheating you’d get a positive answer.

The thermostat and timing belt should be replaced while the cylinder head is off the car.

@asemaster that is a great idea. Are such things common with mechanics to do ridealongs like that?
Also, I am worried that I may have done damage to the engine by driving it as long as I have witha blown head. I may have warped something badly beyond repair, I just don’t know.

If this is the same vehicle you posted about in January then yes you have most likely have done a great deal of damage.

Nope. No way I would send a guy out for an hour to drive a car with a customer. Unless he was paying. The hourly labor rate and lost parts profit from not being engaged productively at the shop would be about $140/hour. And I’m sure I would find some additional charges for taking along shop equipment, etc.

You need to pull the cylinder head and inspect. You may have warped the head, maybe not. But all the wondering in the world won’t tell you if you did. Time to open it up and take a look.

Also, the spark plugs weren’t sandblasted idk if that is crucial or not. How much would you charge to inspect a pull up the cylinder head and inspect head-gasket and put it all back together again?

When you said I am losing coolant in the combustion chamber, this is to say the chamber where the gas air and spark meet? how is coolant be losing there. Bit confused.


If the cylinder head is being removed to inspect the head and gasket, it’s going back together with a new head gasket

Head gaskets don’t get reused

With any luck, the mechanic can visually see that the head gasket has failed. Then the head needs to be checked for warpage. When a head gasket has failed in any way, the head is often sent out to a machine shop to be cleaned up. That means removing the minimum amount needed to make the head “flat” again.

If the head gasket has failed, coolant can enter the combustion chamber, where it will be burnt up.
That is how you are “losing” coolant, in the sense that you need to replenish it.

The head gasket is supposed to prevent coolant from entering the combustion chamber. It sounds like yours may not be doing that anymore.

Oh, I’d expect $1100 or so, but that varies widely depending on your locale. I recently saw an invoice from a repair shop in the Midwest that was charging $70/hour, and known to be one of the most expensive shops in town. Some shops in large urban areas are bumping up the $140/hour mark. All depends.

@asemaster Is that including installing a new one? and possible milling/machining and resurfacing?