Dagriffi

How was/is the fluid level in the coolant reservoir bottle and radiator? The gasket around the thermostat goes in a very specific way, and the housing needs to be cleaned of gunk thoroughly before a 100k change-out -- it's possible that you're leaking there, and would make sense if it were just done and things are a little misaligned.

The no-hot air at idle is likely just air trapped in your heater core. To get rid of trapped air, idle the car with the radiator cap off (removing the cap when the car is cold). It's more effective to raise the front of the car, by either jacking it up or parking on a steep incline.

This: makes the job much easier.

edit: A $10 handheld black light from somewhere like Amazon will make finding the source of current and future coolant leaks very easy.

Jschmidt86

Hello all, This is my first post. I've read your threads prior, and found them very beneficial. Currently I am experiencing a very frustration issue with my girlfriend's 2001 civic EX for which I can find no prior write-ups.

Her car was running fine, but the CEL was pushing codes for engine misfires 1-4 as well as a random misfire code. After replacing many system components I decided to change out the head gasket, even though nothing pointed to compression loss, leaking coolant, tainted coolant, overheating, or white smoke.

Sure enough, there were multiple spots in the gasket which had failed. I replaced all gaskets within the Fel-Pro kit and reassembled.

The car ran beautifully for almost a month, and then came the issue... The coolant bypass hose will eject itself randomly (high pressure I assume) dumping on average a gallon of coolant per occurrence.

She is averaging 31 MPG, no overheating while driving, no leaks, fans seem to work fine, I've replaced the thermostat with a 170 degree Stant superstat, Replaced the bypass hose o ring with a honda certified part, as well as a new radiator cap.

The bypass will eject only after warming up the car for over 15 minutes, and then moving it. It is very cold here in the butler PA region so warm ups are necessary. I just can't understand why she can drive the car all day without a hiccup, but in the morning this has happened 3 separate times. HELP PLEASE!!

Almighty-Si

You would think that a lower temp thermostat would be beneficial but in all actuality, it's not, i'll explain.

A person who will benefit greatly from one of these is a person who thrashes their car pretty hard, doesn't have to worry about traffic, track races etc. In order to fully take advantage of this thermostat, you would need to upgrade the fan switch as well.

Street cars are designed to run typically between 190-200 degrees. This is the temperature car designers consider normal and tune the ECU's accordingly. Running the car at a colder temperature runs the car at different fuel values. It won't cause the car to run poor but, it won't be running as efficiently as it could be.

Also the numbers when buying a thermostat (ie 170, 180) are what is called start to open temperatures. This means if you have a 180 degree thermostat, it will start to open by this temperature but it won't fully open until 10-15 degrees later. By lowering the temperature on the thermostat, the thermostat will start to open earlier (obviously) which seems like a good thing but it's not. When city driving (stop and go) by opening earlier it doesn't give the radiator enough time to properly dissipate heat. If you're consistently moving, it's not a problem (except for running too cool for reasons mentioned above) but if you're in any type of stop and go traffic, the thermostat will never close enough to keep coolant in the radiator long enough to properly cool it and the car can actually run hotter. This will also cause it to take longer too cool once you do start to get going.

Ok with that said, when you removed the cylinder head, did you have it checked to see if it was warped? Was the cylinder head milled? Did you replace the cylinder head bolts when you reinstalled everything? Cylinder head bolts are torque to yield (stretch when torqued down) and can sometimes cause certain parts of the cylinder head to be over/under torqued and after some heat cycles, cause the cylinder head to warp. In my experience, I have never seen that happen but just cause I have never seen it happen doesn't mean it can't.

I would also swap out that thermostat. One, because lower temp thermostat for a street car is not beneficial. Two, because I'm weary about aftermarket thermostats. I have seen many fail way prematurely, some even after a couple of weeks. I would go and get a factory piece. It's not that much more than a stant.

EM2abe

just follow the areas where you see coolant leaking from. get a flashlight. if anything, have someone pour it slowly while you look to see where its leaking from. it could be a bad hose. a hose that was not clamped on well. cheack all of your hoses. in actuality, its not that hard to screw up the installation of a thermostat. the only real way that it would leak from the thermostat is if one of the bolts was look or if the housing was cracked. the no hot air at idle is simply because the motor takes about 15-20 minutes to begin to warm up. the hot air is only going to come if the motor is at normal operating temperature. get the spill free funnel at your own discretion. its not mandatory because you can just use a regular funnel. the same goes for the black light.

EM2abe

next time dont use the felpro kit. this has been stated before.....

ChedWick

I have a 2004 Civic EX sedan that I purchased back in August.

I've been having periodic heater issues since probably Christmas. When I'm driving nonstop my heat is nice and toasty but when I slow down or am stopped my nice and toasty heat turns lukewarm and in extreme cases, freezing cold.

I've looked into it a bit and the most common suggestion is adding coolant, which I have. This certainly helped and the first time I did it, it kept my heater running fine until probably 2, maybe 3 weeks ago. So for a little over a month.

Now I added more coolant 2-3 weeks ago and once again I had heat siting idle, but about a week ago it started doing it again. I just added coolant about 20 minutes ago and while I may not have gave it enough time to kick in, I wasn't getting heat right away like I did the last few times.

My thoughts have been that since I've been adding probably 24-36 ounces of coolant at a time, I have a coolant leak of some kind. I however see no sign of a leak at home or at work where I have the same parking spot. I also noticed that my overflow reservoir is full and I mean FULL. The low and full lines are down in the tank but the actual coolant level is just below the cap. When I look in the radiator it looks empty(after its been cool for a few hours). Looking more into it, it seems I'm not adding a ton of coolant and the excess may be getting burned off. So the other suggestions point toward the thermostat which I'm about to order since its less than 10 bucks. Waterpump, but it was replaced by the previous owner about 20K miles ago(I have all the paperwork from the honda dealer). So I'm hoping that's not the issue but on some rare occasions I have heard a kind of gurgling sound when starting to move from a complete stop. The other big suggestion is a vacuum leak.

So here's a complete list of symptoms

*Cold air blows when idle
*Hot air blows when moving, the faster/higher rpm's the hotter it is
*No visible signs of coolant leaks at home or work
*Coolant level in the overflow reservoir is over full when idle
*Radiator fans do kick on (tho not often due to the extreme cold this winter)
*It seems when I squeeze the top hose to get the coolant moving idle heat comes back almost instantly after adding any small amount of coolant
*Car never overheats
*Very rare gurgle sound when getting moving after a complete stop.

Any thoughts? Any home tests or things I can look for to get a better idea?

EM2abe

have you read ANY of the previous posts on this topic? IF i were you, knowing that your car has not YET overheated, i would switch out the thermostat with a NEW OEM HONDA thermostat. and do that as soon as possible before your motor starts to overheat. Runs a radiator flush. then refill it with cheap prestone. if you're problem does not persist, then you've beaten the odds and you can breathe easy. dont use anything but OEM parts though. i cant stress that enough. seriously. im serious. can you tell i am serious? < thats my serious face. im not joking.

Then if your problem does not persist, i would switch from the cheap prestone 50/50 coolant to the new honda blue coolant. but this is at your own discretion. i am OCD about the coolant, but really the prestone will be fine for about a year or two. the blue honda coolant lasts about 5 to 6 years as per the honda dealership guys i know. DO NOT PUT THIS OFF. it can turn into a $1,000+ problem.

toyomatt84

iTrader: (1)

Considering I merged his thread with this one... its possible that he didn't read through this thread at all. If you look at the top of his post, you'll see the header, and it does not correlate with the thread you're currently in. That's how you can tell the post was merged. No need to get offensive, as he probably didn't have a chance to look through the thread yet.

Dagriffi

I agree, it's easy to screw up the installation if you're not familiar with the design. Tabs of the gasket need to be aligned in the housing grooves, if they're off even a little bit you won't get a good seal.

I think what she's saying, is that while moving she has heat, and while sitting still, her heat goes away.

I think it's odd that coolant is audibly dripping when she filled it. If the leak is that bad at no pressure, it should be a huge leak under operating pressure and I would expect overheating.

Schultz

I own a 97 honda civic and the radiator fan will intermittently work. Ive replaced the thermostat switch, and fan relay. Ive also cleaned the ground connections. i dont know where to go from here.

MacGSX

I'm going to attempt to make this short.

2005 Honda Civic EX...STOCK. Had the motor replaced with a zero mile motor. NEw head gasket, water pump, radiator and as of today another new thermostat.

The car NEVER warms up. I let it idle in my driveway for 1 hour. Never went above the first line on the temp gauge. The upper radiator hose gets hot but the bottom never does. Took the car for an hour ride, it warmed up between 1/4 and a 1/2 on the temp gauge. Got out of the car and sure enough the lower radiator hose was still COLD.

When I put the SECOND new t-stat in I burped the system for at least an hour. The problem is, the car never warms up enough for the t-stat to open.

I have no idea what to do from here

toyomatt84

iTrader: (1)

I would recommend going here: https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/

Chrisk8726

It seems to be coming from the reservoir as if pressure is building up and is blowing out of the cap the car still performs well and isn't smoking but the radiator does not fill back up off the reservoir what could cause this

lazlong

Do you keep having to add water? If so, confirm that there are no leaks then have the coolant tested for exhaust gases to confirm a bad headgasket.

texasgirl

Hi there- I have been lurking on this forum since December when I had started having overheating issues with my 2003 Honda Civic EX and 140,000 miles. I had my thermostat and rad cap replaced at auto shop. There were no leaks. It started overheating again and I took it back to shop. Couldn't find any leaks or anything else wrong. I mentioned water pump and they said it wasn't that?! They also said it wasn't my head gasket.

I notice now that when I turn on my heat it blows cold and then my gauge rises. I pull over, turn car off, turn climate to cold and turn it off. The gauge no longer rises and I can drive all day without problems. But as soon as I try to turn on heat the gauge rises again.

You all seem great at solving issues and I have read through 7 pages without someone mentioning this. I don't have much money and don't want to spend on unnecessary parts. I am very frustrated. In the 2 months of not nothing anything about cars I have learned ALOT about the cooling system!

I am not leaking coolant, there isn't any oil in radiator and my oil is not milky. I am not blowing white smoke, either. Both hoses are hot to touch.

Could I have a failing water pump? Or is it my heater core?

Thank you so much for any replies that can help!

toyomatt84

iTrader: (1)

I'd imagine your heater core is blocked and needs to be flushed (separately from the rest of the cooling system).

texasgirl

Thank you so much!!! I suspected this when I made the connection of the heater problem/temp gauge rising but wanted to confirm. Do you know approximately how much flushing the heater core costs at repair shop?

I am very thankful for this Honda forum and especially this thread!

toyomatt84

iTrader: (1)

Honestly, I wouldn't really know what your local shop will charge for that service. It doesn't take too long, but it will require a coolant flush at the end.

toyomatt84

iTrader: (1)

Not on a 13 year old car, they don't.

toyomatt84

iTrader: (1)

I'm not 100% certain, but I don't think the Hyundai powertrain warranty was offered until more recently. But, I'm not trying to quarrel over something like that. I do not know why the design of the engine was so flawed that headgaskets became such an issue to even consider a TSB, but... alas, that is part of the flaws that are inherit in this particular chassis.

cheesepoofs

I have an '05 civic with 160k miles on it. In the past few months the car has overheated 3 times:

1. First time overheated while driving down a mountain. There was no coolant in the reservoir or radiator. Reservoir cap was missing (blown off?). Refilled coolant, had coolant system checked for leaks (there were none), and car was good for 2 months.
2. Second time overheated after long climb and was again completely out of coolant. Refilled coolant.
3. Third time overheated next day after long drive. Did some better troubleshooting this time

Symptoms:

• Car overheating at low speeds (while stopped)
  * High speeds appear to help (30+ mph)
• Popped hood when car was really hot and fan wasn't on
  * Reservoir cap had popped off, coolant all over the place
• 10 minutes later turned ignition to ON later and fan turned on
  * Started car and fan stayed on
  * Fan shut off few minutes later
  * Drove home (10 minutes) while watching temps
  * When I got home car was pretty hot, popped hood and fan was not on

Also, the heat feels like it takes longer than it should to start working. Used to be able to feel heat as soon as the car became slightly hot, now the car warms up to full temperature before I notice any heat.

Any suggestions on what could be causing this would be appreciated.

DickBean

Even if you COULD vent a small amount of exhaust gas through your radiator, at some point, the engine will cool down and some of that coolant will get sucked back into the cylinder. If that happens enough times, the breach will get larger until enough coolant is vaporized within the cylinder then causing misfiring and that tell-tale white smoke from the exhaust.

At least, that would be my guess of subsequent events.

jimmyhilldrix

What's the "right" way for radiator fans to work? I've been having overheating issues for the last few weeks. When the temp guage was high, I took a look at the fans and they weren't on. I took it to a local shop and the guy said he saw them running. So I took it home and and checked again. Sure enough, the fans would kick on around half way up the temp gage, but would then turn off 8-10 seconds later. It repeated this for a while. Now, after replacing the coolant, the fans aren't turning on at all.

Should I expect them to turn on and stay on untill the temp drops or is the on-off behavior correct?

Also, what triggers the fans to turn on? Is it the same thermostat that opens to allow cooland to flow from the engine into the radiator?

If it helps, I'm talking about a 2001 civic sedan.

DickBean

The thermostat has nothing to do with the fans. It's job is to open only after the engine has warmed to a proper operating temperature; generally after a few minutes. If it's cold enough outside, and you leave your engine idling, the thermostat can be fully open, allowing coolant to recirculate through the radiator but without initiating the fans. I believe that the coolant temperature sensor initiates fan starts/stops: once the coolant gets too hot, it will need to have ambient air pass through it either with the radiator fans or by you moving the car through that ambient air.

On newer cars you may have noticed that after driving somewhere on a hot day, parking the car, then shutting it down, the radiator fans will start as you walk away, then shut off automatically after cooling down somewhat.

The fan should always turn on, and off, at (the same) specific temperatures. However, the temperature gauge on your dash may be reading temperature from a sensor on a different part of the engine. That should be easy enough for you to research yourself. If you have two sensors telling two different things, it's likely that one of them is broken. Since the coolant temperature sensor (CTS) is easy enough to access and remove, it'll be easy to diagnose. Likewise, shorting the connection to start the fan is a simple way to check that that circuit works properly.

Remove the CTS, connect it correctly to a digital multimeter, dip the sensor into boiling water, and read the meter and compare to specifications. If it reads correctly and remains stable, it's likely that the other sensor is broken. However, it may also be possible that some other problem is keeping your engine from a uniform temperature: faulty water pump, cooling system blockage, faulty head gasket. These problems each have their own additional diagnoses. Good luck!

Greylen78

Ok this is my issue. I have a 2004 Honda Civic. So far I have replaced the thermostat, replaced the temperature sensor, replaced the radiator cap.
I have had the system pressure tested, and also properly burped the system several times. I also had it hooked up to a computer and made sure the fans are kicking on when they are supposed to and they are.
I have noticed that the problem only occurs during colder temps. While stopped I will lose hot air, shortly after, my temp while rise slightly above halfway. As soon as I get to moving again my heat returns and temp goes down. At first I thought it might be low coolant, but after checking radiator and reservoir I noticed that fluid is being pushed into the reservoir (which is why I replaced the radiator cap). This only seems to happen with the heat on during the colder months. Recently when I lost hot air and the temp started to rise I revved the car up and it only got hotter. I also tried this with swapping the AC to cold, and this did not make a difference either. Both times as soon as I started to move again heat came back and temp went down.
Really getting frustrated at this point would love some help with this odd issue.
Thanks,
Greylen