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Sorry for the long post, but did not want to leave out something relevant!

Over the years I have had my share of coolant leaks, but this one has me baffled. I searched, but this one is a hard one to search on so I got nothing helpful.

We have a 2003 Honda Civic 4cyl manual. It was in a front end collision before we bought it 1.5 years ago. To my knowledge it has a new Radiator. Well everything has been fine for 1.5 years.

Today we drove an hour to a doc appt. Parked. Car sat for an hour. We then left the parking lot. Were sitting in line to pay and leave. There was a downward incline. When we leveled off we smelt coolant. I thought it was the old truck in front of us, but he left and I still smelled it. I stopped in the center of the highway and looked under the car. We were dripping. Quick peek at the gauge… normal. So I pulled into a lot to check it out. I shut off the car and opened the hood. I expected to see something dripping or spraying. NADA. Coolant was slung around though. It was on the hood… front of motor… rad fan shroud… rad hoses (both)… lower support bar (below lower hose). So I pull out the only thing I had… Mcd napkins and start wiping down what was not piping hot…

I then looked around for new moisture from a leak. Nothing. So I turned on the car… nothing. Then I thought hmmm… fans… turned on AC. They worked. Had my wife rev the gas to see if something would sputter out. Nothing again. OK now what. Gauge was still normal. So we drove part way home and I stopped to check the car again. No new spray. Now I know from the past that if you have a BAD leak you might not even run hot, you will go straight to cold. But this did not happen. Car never ran hot, nor cold. Just smack in the norm. So that told me there was at least enough coolant in the system to give the gauge something to read.

So that being said the wife dropped me at work and took it the rest of the way home w/o incident.

My only thought is a possible leak in the reservoir? It seemed low, maybe even empty. I wonder if it might have enough pressure to spray out till it got below the crack, or maybe the reservoir hose itself? Of note… when we got the car I had to make him buy a reservoir cap because it had none. I noticed the screw top in the reservoir was a bit messed up. Maybe they kept the old one from the wreck??? If it might be the reservoir, are there any DIY instructions on swapping one out?

As most of my knowledge lies with the domestics, are there any other lines that contain coolant I should look at? I plan to crack the rad tonight and take a peek once the system cools, so I can see how low we are.

Would the best thing be to put the car on ramps to elevate nose… refill the rad, sqeeze hoses and see if they leak, let it run the bubbles out (if any), then fill the reservoir. Then see if it repeats the leak?

Thanks for any help you can lend me!

 
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For good measure, I'd flush, fill, and bleed your coolant system. With a loss of coolant like that, you're bound to see some temperature fluctuations..

I've had a few coolant leaks (well, signs of it), and at one point in time, I had coolant that sprayed from my overflow. At least, that's what it seemed like from the dried coolant spray pattern. Me and my buddy also took a peek under my hood one day and noticed a pool of coolant on my front engine splash guard. We filled and bled my coolant system, prolly added a pint or so of coolant, and haven't had any problems since.

 
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Phantom coolant CAN be found with a pressure tester. If nothing is leaking in the closed system, fill the degas bottle to the top with water and dry it all off good then let it sit over night and see if the bottle itself is leaking.

 
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ugh I just typed up the long reply and then accidently hit back and lost it.

So, in summation:

I've been having a similar problem, almost exactly. I have a phantom leak and it looks like mainly it could be dripping from the lower hose inlet, but i have just replaced both hoses, the thermostat, fan switch and rad cap.

It almost seems like it is leaking down from the cap, but it releases pressure (and coolant when hot) when I open it, and it doesnt explain why it was happening before I replaced it.

It collects on the (if you can understand this) the splines that go the the center of the radiator fan just a little by the center, and then collects on the plastic underskirting underneath the lower hose. I see it dried and sprayed on the side of the battery, the air box, and both hoses. Although I have never seen a puddle or anything drip on the ground.

I have yet to actually see anything dripping, so I am at a loss, and I can't really afford to replace the radiator at the moment, although that seems like the only thing left to do. I've even considered using a stop leak product, but I don't think I will. I'd rather keep a jug of coolant in the trunk like I've been doing than have my motor blow up.

Anybody have any ideas what it could be? Could the actually radiator be cracked? Like behind where the fan is and its sucking it out and blowing it around?

As far as pressure testing goes, my mechanic said he would have to remove the radiator and then send it out to a shop to get it tested for flow and pressure. is this possible to do without taking the car apart?

 
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Do what riceboy says and if that doesn't fix it I'd start look at exhaust gases in the coolant.

 
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so it might coming out of the top of the overflow tank?

 
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Sorry for the delay in posting back with my solution. For some reason I have not been getting any notifications of replies on this forum. Even after I checked the instant reply. Oh well...

well I found the problem... There was a hole in the top of the reservior. I assumed it was the issue, so I bought a new one and as I was taking it out to replace the old one I also found a hole in the reservior line. I replaced both.

I then jacked the front of the car up. Opened the rad cap and filled it. Then ran the car till the thermostat opened. Then I filled it again. I let it run for quite some time to see if any additional leaks would present themselves. I even lowered the car and let it run some more. When I was satisified I topped off the reservior and all has been well since.

Based on the tear in the hose I would say it was the culprit. The hole in the top of the reservior has been there since we bought it and has never given me an issue. The car was wrecked in the front before we bought it so I'm sure there was some courner cutting. One of which was replaceing the reservior and line. The line just finally had enough of expnading and contracting and gave in to the split.

 
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Did you inspect your reservoir and its lines at all? I know when my Firebird sliced its lower res hose the whole engine got a bath till the res drained. I was surprised to find my leak there on the civic, esp concidering the distance of the spray. Once I replaced the res and line all has been well.

I had a 90 chevy dually and and 87 bird that both had a mild radiator leak. I was able to buy myself some time and patch it with the pour in metal flakes. It was a small leak and by no means was it a permanent fix. I have not had this patch fix ever hurt an engine, however I have only used it on older domestics.

I worked at a dealership and had them look at the truck and they said it was the rad. They never removed it. So I would hope someone could dye test it in the car. Places are getting so specialized nowadays though. Try going to a rad shop yourself. See what they say, or call.

Over time the dually got so bad I could not drive it far w/o have to fill it up. I ordered a new radiator was going to swap it. Then the truck was stolen. I got it back less the engine, tranny, and rad. Hope it blows in their face! The bird we also saved up and eventually replaced the rad. You can get stock replacements for domestics at most parts stores. Hopefully its the same for the imports.

 
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I dont suspect it is the overflow because it is ALWAYS full to the top. The actually radiator is what empties, which is weird, because isnt it supposed to pull from the over flow when that happens? And if the overflow hose was leaking, would that tank empty and not the rad? or at least both. I have to fill it up about every day now, so I may try replacing the overflow hose, but I am basically having the same problem except my overflow is always full.

 
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I also have an 88 suburban and I've put 2 radiators in that and then had to weld patch the last one because I lost a pair of vice grips in there between the rad and condesor. :-P I wish this damn civic was as easy to work on as that is.

 
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no, the radiator will have enough vacuum to pull from the tank if there are no leaks. if there are leaks, when it cools, the system cannot generate vacuum for the air will enter wherever the vacuum is trying to form.
So, the tank does not seem to be the culprit, is all we can say. The hose might still be one.

 
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so if that is how it works, it seems there would be a leak in the actual radiator? Because if everything is sealed right, then if the radiator level lowers, then it should pull from the overflow. but because it isn't pulling from the overflow, then there might be a leak in the radiator block itself?

If it was the overflow hose, then the overflow tank would be losing water as well, correct?

 
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So I figured out that my problem is at least definitely a leak in the radiator, and my friend who is a retired mechanic said the reason why my overflow isn't being drawn from is because my rad cap is not functioning correctly, but it had happened with the stock cap too.

So I have it fixed for now, and used a great alternative to all the stop leak products out there: Fine ground black pepper. The pepper works like the stop leak, except it won't clog anything except the leak.
I put about 1/4-1/3 cup of ground black pepper in, straight from the packets you get at take out restaurants (about 30 of them) and dumped it in the radiator, filled it up, and viola, no more leaking. As far as I can see, there are no more drips on the lower splash guard, and definitely nothing being sprayed around.

So for now, I've got that problem solved, not sure how long the pepper fix will last though.