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Honda Experts,

I have a coolant leak, couldn't find any leak in the radiator, so I took off the overflow container, drained it, put it back on and discovered:
Coolant is slowly escaping thru the overflow tube. It starts filling the container.

My question is:
Why is coolant coming out the overflow tube?
Is this a symptom of a bad radiator cap?

It doesn't overheat (if I have water in it)
It's a 2003 Civic LX

Thank you,
Kevin

 
Rep Power: 199

Check it for hydrocarbons. Sounds like a weepy HG to me. You might try a rad cap, but doubt it....

 
Rep Power: 517

You do not run with an empty reservoir.
It is there for a purpose. It is supposed to.
Unless it is too much.
If everything is working properly, the radiator always stays completely full and the level in the reservoir changes with engine temperature changes.


===

If you had the reservoir out and in your hands, then you surely saw the lines indicating MIN and MAX on the sides of it. (MAX line does NOT mean completely filling the bottle!)

Now:
With the engine cold and the radiator completely full, fill the reservoir to the MAX line.

Put the caps on.

Drive it.

Let the engine cool down again for at least a couple hours or more. See where the reservoir level is at.

Is it still at the MAX line, or somewhere close to it?
Is it now significantly lower than the MAX line?
Is it significantly higher than the MAX line?

If it barfed a bunch of coolant out of the reservoir, that's a problem.

 
Rep Power: 185

When you say "problem" do you mean a head gasket job?

 
Rep Power: 517

Not necessarily.

 
Rep Power: 0

Thanks for your response.

John Deere Guy, My only JD is a STX38
Hydrocarbons: Is that on a smog check? Could you tell me more? What would it tell me?

ezone: Yes, too much coolant ends up in the overflow tube. It drains the radiator. The coolant never goes back into the radiator. It's not working correctly.

When the problem started, the overflow was full, and coolant was getting all over the battery and that area. I had to drain the overflow container as a troubleshooting step, to figure out if I had a radiator leak or not. When the overflow container has space, then the water goes into it, and the battery/car side stays dry.

I'm trying to figure out why all my coolant is escaping.
If you have any ideas, that would be great!

Thank you,
Kevin

 
Rep Power: 185

Unfortunately, this is a typical symptom of a blown head gasket in these vehicles. You can wait for others to reply, but based on my own experience, that is most likely your issue.

You can have a shop or yourself verify this by blowing 170 psi(recommended by ezone in other threads) in to each cylinder via the spark plug tube and monitor a fully filled radiator. If you see bubbles consistently coming up, it's the head gasket.

The coolant is leaking between the water jacket and the cylinder head and is allowing the cylinder pressure(180-220 psi typically) to pressurize the coolant system thus blowing the fluid out the reserve tank/overflow and partially emptying the radiator.

 
Rep Power: 208

= your head gasket is blown

 
Rep Power: 517

Do I even need to agree?

 
Rep Power: 185

Yes. If you don't, all information above is invalid. I'm only speaking for myself since I'm not a mechanic.

 
Rep Power: 199

LOL I couldn't care less about you air cooled stx absolutely no bearing here. Hydrocarbons and the "leftovers" from combustion. Ideally there should be none at all anywhere in the coolant system. A commercially available sniffer is a tool, if you have any mechanic buddies maybe they will let you use one, if not NAPA sells em. If there is any evidence of them in the system the normally blue liquid used in them will turn green doesn't matter if it was a few minutes ago or days ago. The usual place "sniffed" is the recovery tank. Like ezone said though, the idea is a closed system when the system heats up the radiator cap opens to let any excess coolant out, the Degas "common term recovery bottle" catches catches it, then when it cools back down it lets the coolant back in via the vacuum created. The reason there is a min line is so that the vacuum ALWAYS draws in fluid, NEVER air. Like ezone says, it is imperative to more and more vehicles to have zero air in them ever, especially our cars. The most common here is headgaskets for sure, but any overheat condition will cause more to be put in the tank and out the top, then there isn't enough to refill it and keep the air out. If it happens every time the car runs, probably overheating. If you bleed it and it goes a few days probably something else, like a slow leak or a hg. That is not 100% though, just ideas to check. The principal to keep is K.I.S.S. (keep it simple stupid) (not an insult, it is a well known acronym) Start simple to complex. First check for a leak, make the level right, bleed the air from the system and double check the level is right, then go from there....