This has been going on for 6 months now.
2003 Civic DX 305,+++ miles
when car gets into normal operation temp, it seems like the whole coolant system is pressuring up and either leaks or blows a hose. I've have the inlet hose go first, then the overflow lines to the reservoir. Runs about 200 miles then starts to get hot. Pull over wait 30 minutes add about a quart of coolant good for another 200 miles. So far I have replaced (some parts twice)
thermostat
reservoir
all hoses
radiator
*Symptoms still exist.
Yesterday I removed the thermostat and cut out a gasket and used permatex to seal. Let car run for an hour. Normal operating temperature. Took it for a drive. Temp running really low due to no thermostat. Heater worked fine. Well, got to my brother's, checked for coolant leak, still same leak. It seems as though system is so pressurized, that it has to find an escape route. All of the previous hoses that leaked or blew out, are v replaced with new hoses and I had to hose clamp everything, even the reservoir hoses. It seems to me that bottom connection on reservoir is where it has the last path of resistance and, that where the coolant is blowing out. I also notice that the reservoir is not draining properly back into radiator. It has no problem filling reservoir up. Noticed bubbles in reservoir last night but coolant was cool in reservoir. I checked temp on coolant in radiator. 164 without thermostat. I have been on every thread that mentions honda civic. Everyone says head gasket. Well, no oil in coolant, no water in oil, no smoke from tailpipe. I am leaning more towards a water pump but, the water is flowing through radiator like a big dog. The radiator nor the thermostat was bad. I guess I just like buying parts to be let down. Any help would be greatly appreciative. If you've had the same problem and have diagnosed and corrected, I would love your input. The car uses no oil, runs perfect and gets around 42 mph. No upgrades or fancy stuff, all stock. I have driven from Illinois to Denver 10 times and, Illinois to DC 10 times in the past 6 months. As long as I stop every 175-250 miles let cool down and put that additional quart of coolant in, I can make trips. I'm tired of stopping. Please help me out. Thanks

 

Coolant Leak and overheating

 

2 civics with pretty much the same same symptoms. It would over pressurize and flow out the overflow tank. They passed all test, no oil in coolant or coolant in oil. Don't burn oil, no exhaust in coolant. I replaced everything on both. Water pumps to hoses to radiators and thermostats and they still did it. Flushed and also bypassed heater core. Same.

Replaced head gasket on both and both work great now. 1 I did myself with a gasket kit from mizumo on eBay. 8,900 miles later it still works great.

$50 for gasket kit
$50 to resurface head. Machine shop showed me it was at least 6mil warped in center.
$50 for a spark plug insert.
8 hours work
7 hours of messing around.

 

I have to say it does sound like a head gasket. You don't always get a breach between water/oil... sometimes the breach is small enough to be just exhaust gas into coolant, but not coolant into exhaust, which explains why no white smoke in exhaust and no water/oil mixing (aka chocolate milkshake).

If you are (understandably) apprehensive about removing the head based on some asshats from the internet telling you to, I think there exist some dyes that you add to your coolant to verify the presence of exhaust gasses. Meaning (I think) that the dye changes color once exposed to exhaust gas. So doing that test will tell you with certainty. The other (more expensive and less definitive) option is to perform leakdown testing on the cylinders. More expensive meaning you prob don't have a leakdown tester handy, and less definitive meaning you may know a cyl is leaking, you won't know for sure if it's through the valves, the piston rings, the head gasket, or a cracked head or block. Not unless you spot the same bubbles in your coolant expansion reservoir while observing a drop in pressure on one of the cylinders.

In the long run, cheaper than 1. new car and 2. a gallon of coolant every 1000 miles (assuming you do the work yourself).

I've done a few heads in my time, currently buttoning up a new head on a VW TDI. Hondas are much easier to do.

 

Actually, one last thing... did you try a new radiator cap?? The rad cap should open to the overflow tank at 1.1 bar I think, 16 psi. So if hoses are popping off, it kinda sounds like the rad cap isn't opening up.

At first I thought your post said it was verified, but I just skimmed it again real quick and didn't see it.

But if the rad cap is known to be good, then ^ above post is valid.

 

What up with the asshat comment?

radiator cap is a good idea to check but in my instances the leak was the cap because it was doing its job and releasing pressure and coolant into the overflow. The cooling system should not get over 16psi.

Also try to check your radiator if you haven't already or already replaced it. I doubt it would be clogged unless you have been putting straight water in it for extended periods of time. Months or years.

the dye that I tried doesn't go into the coolant. Rather it sits in a vile over the filler neck in the radiator. You idle the car to temp and check for exhaust gas coming out of the radiator. Both my cars passed this test and a leak down. I believe it's because the leak doesn't start happeneing until you're at highway speed. It's small enough that it takes a couple of hours at highway speed before it starts to overheat.

 

Everything is new from cap to thermostat. Radiator, radiator cap, reservoir, reservoir cap, all hoses that have coolant running through them. Before pulling off the head, which I'm very capable of, I was thinking trying a head gasket sealant. I've researched a couple of high dollar brands and, read reviews. I really really doubt it would be that easy of a fix. Anyone tried a sealant? Any input as to why is a bad decision?
thanks guys

 

I bought and have used the kit bb wrote about. The liquid turns color to let you know HOW much exhaust is leaking into the coolant system. I think it is worth the money.....several u tube vids showing how it works. As to the sealant, in my younger years of car repair I have used different sealants as quick fixes. Most just caused me more headaches when time to go in and fix the problem as should be. I did get some long time usage from a leak sealer for my AC system one time. Most of the coolant system sealers helped stop up the radiator. from full flow......but I am sure there are new sealants available today.

 

well he doesn't know me, I may be an asshat. and for him to start pulling a head based on what I say is at best risky. same goes for anyone else on any forum.

the amount of poorly thought out advice and flat out misinformation (intentional or otherwise) I see on forums all the time... it's important to realize the person answering your reach for help could literally be a 12 year old. well, not me... assuming I joined the forum on my first birthday, I'd have to at least be 16 roughly. lol

 

In your case, no. That product will not work. Pretty sure NO head gasket repair product can work given your failure mode.

You say no coolant in exhaust and no oil in water. Only exhaust gasses bypassing out. Makes sense, cylinder pressure is north of 180 psi on a healthy d series, and coolant pressure is 16 psi. So a leak going one way but not the other makes sense. So how do you suppose the leak-stop product will get into the area where it is needed? I don't keep up on the latest in temporary fixes (I don't mean that as an insult, I don't know how else to say it), but the product you would need is something that would be part of the fuel and would deposit itself into that area under combustion. I doubt something like that exists, but I don't know.

And trying something else will just make the cleanup job that much worse when you go to replace the head gasket. The stuff turns into a hard gel like substance and it is a pain to clean up to make the right passages clear again. Leakstop products aren't selective, they plug up everything, so cleaning them out sucks (that includes your rad, waterpump, throttle body, block, head, everything...). Sadly in your case, since coolant isn't going into the combustion chamber, they wouldn't plug your leak.