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By cirrus, March 2, 2014

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Hi guys.....always great well thought out advice here(like the intake gasket on my 2005 rolla) so told the wife I'd ask here even though its not a Toy but should be an issue any car can have.

Our 2002 Honda Civic has this issue when its idling and the heater is on...the air is cool....yet get the motor rev'd a bit and its nice and hot.

Its never overheated....runs great at 122K loss of antifreeze in the oil. The dealer said right away......"heat gasket". I was floored!

I thought maybe bad thermostat though then I'd think I'd see that on the temp gauge....or something in the heater core. They said probably not.

Why would a head gasket cause that????

Could a bad radiator cap cause it....or thermostat?

Any ideas to check on be great!



Could be a number of things. T-stat is the first thing that pops into my mind - faulty T-stat could be partially working, so the car won't overheat under normal conditions, but won't provide hot air. Waterpump could be going, not able to circulate the coolant as effectively as it should. Vacuum leak - not sure if this year Honda uses a vacuum source to control the blend air doors in the HVAC system. Cooling system could have a bubble in the system, more so if you've just had a cooling system service or if the coolant recovery tank ever ran dry. Plugged or damage heater core + hoses running to it could also be a cause for issue.

Blown headgasket - unlikely. For a blown headgasket to cause your heater to act in that manner - has to be guzzling coolant. Since coolant levels seem good - engine temps are OK - this is very unlikely. Dealership sounds like they want to pry some extra money from you. The definitive check is an used oil analysis to check for the presence of coolant in the oil and a coolant test to see if hydrocarbons have bubbled into the coolant. Without those tests - you can't say a blown headgasket without any sort of certainty.

Caveat - there are a fair number of 7th gen Honda Civics that have seen blown headgaskets, especially if the miles runs past 100K miles. More likely to see this when it gets closer to 200K miles. Usually the first sign is that the car is loosing a significant amount of coolant.

Hi FIsh...thanks very much for the reply...just in time too.....the dealer is finding a lot of stuff wrong with it....thing has an external oil pump???

But they want $3000 to replace like everything...head gasket and a ton of parts with that....the exhaust manifold has a leak (and of course the CAT is part of it) and this and that.

What is irrating me is I'm guy who likes to diagnose stuff fully. Do a leak tests of the cooling a block test for gases in the exhaust....check the flow from the water pump. They haven't done that and said their tech is 99% sure its the head gasket. He might be right as like you said this is a common issue. Or is this like...same model car....bad struts at 40K miles they had everyone replacing. I way....and at 122K the can is fine with tech says they are bad. So who knows if these head gaskets were really bad.

To me I cant see it being the head gasket! Its not overheating...nothing looks to be in the oil and its not using antifreeze. Oh....good one there...they said to me...."its low on antifreeze too". I filled it up actually abit to much in the over flow yesterday....and I watched the radiator always had antifreeze flowing up near the cap. When I dropped the car off...same level.

Lets say we keep driving it....and its the gasket....if it does start putting it into the oil that can really screw up the motor right?


External pump!? Only if you mean it sits on the engine instead of inside the engine. This gen's Honda is not any different than on the Corolla. Sounds like this dealership is living up their namesake of "stealership". They want to just shotgun the repair - don't diagnose anything, just replace parts on your nickel until they magically "fix" the problem. Worse case, they actually do a diagnostic, find the trouble part - but still charge you for all the other unnecessary work to pad the repair bill.

I'd try another dealership if possible - or if you have access to a good independent shop - have them do a diagnostic. Much of the chemical testing, you can do yourself. Used oil analysis companies can send you test kits to sample your oil, ship them the sample, and wait for the results. Same way with coolant sampling - some actually give you the chemicals to mix with coolant to see if there are traces of oil and/or hydrocarbons (pH testing).

Playing Devil's advocate - say it is a bad head gasket - if you kept driving, it will eventually contaminate the engine oil (see engine oil take on an unusual color, look like frothed chocolate milk) and you'll blow coolant everywhere (gases get into the coolant, and push past the pressure cap easily). Even then, the car might run for a couple of thousand miles no problem. If it see something catastrophic, like a cylinder filling up with coolant and you blow a rod though the block - it will still cost you less than $3K the dealership wants to "fix" your car and swap in a replacement engine.

That's what bothers me....I asked what tests the tech has done....just a few simple ones but he is 99% sure its the gasket. I suggest the other tests but they balked saying it gets costly. Now the issue I told my wife...I cant ask them to do the tests as they'll never say..."hey you were right...its the water pump or thermostat...". you said...they'll change that part but still do the head gasket saying it was that. THe guy who did the water pump/belt didn't use a Honda one...which is no big deal....but he might have used a cheap one that maybe now is falling apart on the impeller side.

Also they said for sure if the head comes off it needs to be machined down so he set that up with a local shop. Funny how fast they feel they need to do they know something about this issue and whats coming?

Maybe he's right....and its that....the service guy is great guy and has helped us out before....but I just like more testing done first.

So....we are getting the car back tonight....and I'll see about getting a 2nd opinion.

But also this has been going on with the heater for like 2 months now....if its blowing into the cooling system I'd think I'd see it coming out the over flow at some point by now.

If its sucking it into the motor I'd see it sucking the radiator dry....right?

So I'll keep a close eye on it.....what oil testing labs do you guys use for the oil?

Thanks for the help!

Yeah, if there is any loss of coolant, whether it is being blown out cooling system or consumed by the engine - your coolant recovery tank should be changing levels by a considerable amount. When it gets to the point where it affects the level of coolant in your radiator's tank - then that is bigger/worse problem. Usually, if you are consuming coolant, you'll get a sweet smelling exhaust odor and there will be a prodigious amount of white smoke produced as you drive.

I've used Blackstone Labs for used oil testing - - standard tests run about $25 per sample, they will send you a free sampling kit if you request one (two plastic containers and mailer). You can pull a sample through the dipstick tube (have to purchase their suction kits or use something you might have at home) or drain some of the oil from the pan, taking a sample after the first couple of seconds of draining (easier to grab a sample, oil flow will be reduced).

I agree with your - they seem to be way to eager to point this to a bad head gasket. Either they know something we don't know - or they are just going on what they've seen the most lately, possible quotas, etc. Testing being more costly is pretty hard to believe - unless they can show you definitive signs that the head gasket is blown (ie, the more time you waste, means it will cost you more money down the road). The radiator hydrocarbon gas test is pretty quick. The last time I saw one - it was at NAPA. Looks like a clear plastic tube filled with blue liquid (dye) and a rubber stopper in one end, aspirator bulb on the other. You jam it into the neck of the radiator after the car has been warmed up. Squeeze the aspirator bulb a couple of times to pull any gas out of the radiator / emissions from the coolant. If the blue dye turns yellow - you've got gases escaping into the coolant. For oil tests - send out the sample, takes about a day for them to test it, depending on how backed up they are on their queue. I usually get my results emailed to me within 48 hours of sending the sample to their shop.

Oh yea if the motor starts guzzling antifreeze you will see it!!! I once had a cylinder crack and the smoke screen I left was HUGE....I mean as high as the telephone pole wires and wide as the road!! Cars behind me had to stop completely! One guy raking his lawn was laughing so hard as I stopped in front of him saying...."man I've never seen a motor grenade like that before!!".

Blackstone even allows me to just send oil in from my end without their kit. Cool...I have special capped bottles I can use...same some mailing time.

I don't get that either with how long testing would take. I've seen Utube videos on using those block tester kits....whats the big deal? I think Advanced and NAPA even rent them out....look into that tomorrow.

I'll get these tests done and keep a close eye on everything.....they might be right...but I need more testing yet to say go ahead with the job.

Thanks for all the help!

No problem - let us know what you find out! Even though this is for a Civic - the testing and diagnostic tests would be the same for other manufacturers. Good Luck.

For sure I'll let ya know as something is going to happen unless we trade it in and I let them fix it. I've been net searching for this issue and I see a lot of issues like this but a lot less updates on what fixed it. Some have said its the head gasket....others the water pump. That is where I think it might be but doing that isn't cheap either.

I was reading the report after getting the car. He says its burning the coolant internally. There is a fairly reputable indie garage down the road from me that deals mainly with Honda's....see him on Monday.

But I've been trying to really understand this....I'm just rambling here...... idle the heater air is very cool....the minute the car idles it goes cold but the minute you race the motor its hot air again. At first I thought for sure a vacuum leak but from what I'm reading this car doesn't use that method to control the blender door.

It its the gasket what the heck is happening? If its pushing air into the cooling system something has to come out. The overflow unit.....can just air go into that or does coolant have to go with it too?

I'm going to run the motor and look for tiny bubbles in the antifreeze via the radiator entry....I'd think if I see anything there it probably is the gasket. I don't get it though if it is....and there is this air bubble in there....why would it go from hot to cold back to hot that fast?

The tech says its burning it. Okay I'll watch the level but seeing anything in that overflow is almost impossible even using a light. Wonder how high should it be in the radiator with the cap off it? He said it was low this morning. I find that VERY hard to believe as when I ran the car on Monday night....there was always coolant over the fins in the radiator and the over flow....when I could see it...was at min when it was cold and I ran it with the cap off and hot and again the coolant was right under the radiator cap opening.

But if it is burning the heck is that affecting the heater? Plus I'd think it'd be backwards...heat at idle nothing once the motor is reving away as it sucking in the coolant like crazy. can be very weird with news soon....default_smile

Compression test might show if you have a head gasket leak or not. Sometimes, you'll get bubbles to actually run out the radiator neck during this test - but usually, it has to be pretty bad to get to this point.. As for coolant levels in the radiator - I've always seen it run to the top of the neck of the radiator, no air pockets. If the level is just barely covering the fins of the radiator - might be a coolant leak,

As for heat only when revving the engine and cold at idle - could be either a bad water pump (damaged impeller), or as the tech mentioned, bad head gasket (air bubble could be trapped in the cooling system). Honda's are picky about these cooling system parts, aftermarket waterpumps can corrode very quickly.

If the impeller is damaged, it will not be able to move enough coolant through the system and through the heater core. If it was a head gasket, there could be a bubble of exhaust gas pushed into the cooling system. Have to rev the engine to get enough pressure from the water pump to push that air bubble out and through the heater core. With both issues - it will be almost a "light switch" effect of going from cool to hot air.

Could pull the plugs and see what they look like. Even the tiniest bit of coolant leaking into the combustion chamber will contaminate the plug - depending on what else was deposited in there, a coolant contaminated plug may look unusually clean compared the other plugs. Might also have a shiny appearance. Many times, there will be a break between cylinders and you'll see two adjacent plugs that look visibly distinct compared to the other plugs.

Here is a good description of different HG failures on Honda/Acuras and possible diagnostic approaches.

Hmmm....I cant "quote" your reply......anyway....

Right now...and the when I first checked it last week....the coolant was over the fins but not really right to the bottom of the neck. Maybe I should fill it and watch it. One big issue is I cant see the level in the over flow tank....I cleaned it...used a flash light...rocked the car...cant see it....unless its empty??! Issue is if I add some to it and its to much it cant be drained without removing the whole thing. Don't even think I can snake down a piece of thin flexible hose.

I too thought if it was pushing air into the system via the head gasket then a bubble might be in there. It doesn't have a bleed valve I ran it around without the cap on...up some see if it would push the air out of it. Then if it did....and the issue came back with that would point to a head gasket I figured. But that didn't solve anything.

The tech said its burning the coolant....hmmm...if the bubble theory holds as far as why its causing this does sucking coolant in cause that? At some point sucks in air via the over flow?

The former non Honda tech who did the water pump I believe used a NAPA one....that's who caters to our local small garages and he for sure he uses them. Issue is getting at the pump is not easy as it runs off the timing belt.

I might see try the block tester....our local store has one....about $40 to try it....might tell me if its leaking. And watch the fluid some point...esp if it sucks the overflow dry....its going to start showing via the radiator.

I found that exact link last night and was reading it. Only thing he didn't have was what this tech said....coolant leak into combustion chamber.

The tech might be right....but unlike with my Corolla where my dealer (I have an excellent deal with them) told me right off with that code...don't go changing the O sensors or MAF....its the intake gasket for sure...we've done several of these on the 2005's....the Honda tech isn't saying if he in fact has seen this happen a few times hence him wanting to skip all the tests.

What I might have them do is skip this so called leaking oil pump that he says is on the motor block....the leaking exhaust manifold( it does have a crack) that has the freakin CAT attached to it and costs $1100.....and just do the head gasket and water pump/timing belt. But first drive it and keep an eye on it.

Shouldn't suck in air at the overflow - unless the tank is bone dry. If there is a leak into the combustion chamber - water will be siphoned into the cylinder under vacuum and exhaust gases pushed out on compression/power - that's where the air bubble will come from.

Wouldn't hurt to fill the radiator tank to the brim and monitor if the level drops any. Assuming the system is completely purged of air - it should not drop any. If there is excessive pressure - it will blow it into the overflow tank. Might be a useful test to see if the overflow is empty - if it is, leave it that way and see if coolant makes its way into the tank. That would indicate a possible air bubble pushing its way through the cooling system.

NAPA aftermarket parts are actually pretty decent. Lots of dealerships and independent shops will use NAPA parts if they cannot get OEM.

DUH my part with the compression....of course. I think the tech saying it was just sucking it in had me off on the wrong path.

For sure have some stuff to try here....and if it does end up being the gasket that's least now I wont feel like I had to make the call at that very moment on what is a lot of money for a 11 year old car. Esp seeing how I've been eye balling the new Rolla's....or a older Camry.

I'll post what I find and in the end what happened!


Mini update Fish: This morning after the car sat all night a 5F I took the cap off and started it and let it run with the heater on. The coolant was down to the bottom of the neck. Within minutes...even before it was warm...several big bubbles came out...and it spit antifreeze out of it. I let it run...a few more bubbled then it stopped. I took it for a it real hot....came home and took the cap off. Wasn't under any pressure to speak of.

But I did notice one thing...I didn't see anything in the I removed its tube and blew into it. And there wasn't anything inside of it. Hmmmm. So I added antifreeze to bring it up to minimum level and watch it today and tomorrow.

The whole time the gauge never went above half way. Later today or tomorrow I'll see if the parts store has that block tester.

Update #2

We took a 2 hour ride.....the coolant was right on the MAX mark....we get back and its down about 1/2" in the overflow tank. That's not much...but maybe it is sucking in some. I'll run it more tomorrow and see if it keeps going down. If it does I guess its not the waterpump/thermostat....probably the gasket.

Update #3

I got a free loaner of the block tester....its a single stage one....not sure how accurate these are. But....with the motor temp gauge at mid way....I checked the rad fumes for a good 5 minutes....nothing....the fluid stayed blue as can be.

So then I'm reading the bottle of testing fluid and it says to try it cold too...the tester instructions just warm. So right now the motor is cooling down.

But....and this might be normal....but I went to drain the coolant out of the rad to redo the test....after it ran for a good 15 minutes with me racing the motor up now and then....very cool. That kinda surprised me.......maybe means the motor never got hot enough to open the thermostat...or its open all the time?

See how the next test goes.

Okay final update....not sure what the heck is going on here!

I tested it cold...fluid stayed blue....I let it run and run....then the upper hose got hot....still blue fluid....but then I think it puked up some antifreeze into the tester as some was spitting out and it turned it green....but never yellow. I thought its probably the coolant so I redid it....still blue.

I noticed a few things....the upper hose got hot.....the lower one just abit warm....even after a run around town and down the highway.

What the heck is this thing doing???

I'm wondering where that temp gauge sensor is and if its a true indication of what say the head area reads?

Not sure what to do. My wife wants me to get a 2nd shop to look at it....maybe should do that real soon.

That temperature gauge has a pretty slow response and narrow temperature window (poor resolution). So it will generally not show "hot" unless the cooling system is in really bad shape.

Sounds like the thermostat is working OK - otherwise you would not get a temperature differential from the upper and lower radiator hose. That exhaust gas leak dye is pretty sensitive - so if it didn't change color - unlikely you have a bad headgasket. Sounds more like trapped air in the cooling system and/or a weak waterpump to me.

When you purged the cooling system - did you run the car with the heater turned up all the way? Is the heater working at idle now - or only puts heat out when the revs are up?

You are definitely diagnosing this the right way - sounds like it could be an intermittent problem (can be a nightmare to diagnose) or might just need more sensitive equipment to diagnose the issue. A second shop's opinion might not be a bad idea. They may diagnose this from another way.

I did find the sensor for the temp....its right at the thermostat housing so its reading right.

I agree it might be a weak water pump. But to even get it changed by the dealer is like $600 and the small garages about the same. If the timing belt needed to be issue...just do it, then if that didn't fix it move onto the head gasket.

I have one last test I'm going to do on Friday night. The guys at Autozone have been great and told me the have a free loaner to test the pressure of the cooling system plus checking the pressure as the motor is running. For sure I'll get that and see.

If that shows nothing then I'm really leaning toward the water pump (wish there was a way to check that) or an air pocket issue.

The thing did the air pocket get in there? I wonder.... when the dealer checked off the box saying coolant was was actually empty in the over flow tank. Could it have sucked air in that way?? I don't drive this car hardly at all and my wife hardly notices things wrong with it so who know how long this issue has been there.

I tried getting the air out by driving it abit without the cap on....but even this morning it still blows warm air at idle....then hot at speed.

Darn....since I posted this I ran into a guy who said his gasket had a tiny leak in it....and his passed most tests...though...he said his was running very hot. Mine never does that no matter how I push it on hills....ect.


If the coolant recovery was empty - it could have siphoned air in as the engine cooled off. I'm also leaning toward a weak waterpump - but a blown HG is still a remote possibility. You could have a small leak between the cylinders that is pulling some coolant from the water jacket - but not enough to show up on the quick tests. You could still drive the car like this - Subaru guys have a bad history of blown head gaskets - but they still drive their cars around no problems.

I've been watching it to see if its using far so good. As we decided we'll probably trade it in....for either a 2013 or 14 I don't want to put any more money into if I don't have too. But that wont be for a few more then I'll really know if its the gasket getting ready to go. Its not aging well vs our last Honda (or hell even my Contour) so even my wife said maybe its time to trade it in.

I'll test the coolant system with the pressure tester....if that's looks fine I'll leave it. I probably should get a small garage to test the compression of the cylinders....but wait on that for now.

Thanks for your help Fish!

Darn....went to celebrate my B day tonight so we tooled around abit in the car and when I got back it looked like it sucked the coolant out of the overflow. The last two days it was steady between the min/max lines. I'll pick up that pressure tester tomorrow night and test it but it appears coolant is going somewhere. I can smell some when I pop the hood...but cant see any leaks. Maybe using the pump pressurizing the system will show me if there is a not then it must be going into the motor.

FIsh.......Well I got the tester but they didn't have the right adapter. DARN!

I'm going to ask the garage that sells me the tires if they can test it as they do radiator repairs too.

One thing I noticed....with the car well up to temp and the heater on....I was feeling the two heater core hoses. I believe the upper one (it also has a control valve on it) is the inlet to the core.....that's hot.....the bottom one almost never gets hot until the upper one is really hot and even then its more a warm feeling. I turned off the fan to see it cools the coolant in the core which would make the exit hose cooler but it didn't.

Hmmm.....maybe an air pocket in the core? Or a half plugged core?

I think there is an air bleeder valve but its almost impossible to get at. Whats the best way to get that air pocket out?


Pressure from the water pump should be enough to push the air bubble out - but sometimes a clogged core or a heater core that siphoning air (leaking) can cause you grief. Clogged core is almost unheard of now - but still a possibility, if the water used with the coolant had lots of dissolved minerals or the coolant was mixed with a different type/chemistry.

Might be able to just flush out the heater core - never tied it myself, but should be like flushing a radiator. Just to see if you can dislodge any physical debris from inside the core.

Okay last test.......

I bought a cheaper pressure tester for the coolant system. I wish they had given some type of "control" plug to be sure the whole unit wasn't leaking. I did find a small one that I fixed.

First checked the cap....seemed fine.

Then did a static test of the cooling system. Ran it up to 4 minutes it lost almost a 1psi. I don't know if that's good or bad. Could be anywhere to lose 1psi over that time. I didn't see any leaks but couldn't see behind the block where the heater core hoses are nor inside the car.

Then did a dynamic test...tester at 0psi....motor cold but running.......right off the bat it went up about 1/2psi but it pushed some of the antifreeze up into the the motor up and down didn't do anything once it hit that 1/2psi.

I then pressured it up to 10psi and keep the motor running.....the needle was solid....not bouncing around.

BUT....I raced the motor up and down and again the gauge went slowly up and down about 1psi...maybe that's normal?

If that's from the gasket leaking then why didn't the block tester pick up anything?

So....not sure what any of that means.....maybe a small crack in the gasket...air bubble somewhere still.....?.

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