04CivicTrouble

I'm new to the forums and though I looked for similar threads describing my problem, I was unable to find anything directly. I'm having a problem with the engine temperature gauge spiking at the red line when I turn on the defrost. Sometimes it actually seems to jump around quite a bit as it proceeds to the red line.

So far, i started with the thermostat and had it replaced. Also at that time, i had the coolant completely flushed. The problem wasn't fixed and the next step was to make sure there were no air pockets, so I bled the lines again.

Unfortunately still no luck so I went ahead and had the water pump changed. It was about to go anyway so it was a good move, but even after the water pump was changed the problem still exists.

Specifically, everything is "fine" until I turn on the defrost. Not only does it blow cold air (it takes forever to even get to "warm" air which was never an issue before) but that's when the engine temp gauge begins to jump around and proceed toward the red line.

I'm at a loss so I figured I would get some advice before doing anything else. I'm worried that the dreaded "head gasket" is one possibility, but looking for anything else that I'm missing before I go down that road. Thanks in advance.

BlueEM2

iTrader: (1)

Kinda sounds like a head gasket but the defrost thing makes no sense... to me anyway. Your fans are supposed to kick on when the defrost is on ( I believe ). To test the fans turn on the AC and check if the fans in the front are on. If not that could be your problem.

The only reason the car would blow cold air is an air pocket in the coolant system or a plugged heater core. So you have to figure out why it's doing it. Is your coolant overflow overflowing?
Change the rad cap.

If this does not help, get a head gasket check done at an auto shop.

sdaidoji

iTrader: (1)

I would be suspicious of the electrical system itself. If you have access to some sort of temperature gauge, i would check if it is really overheating (not easy, for the tempearatures in the engine block outer case are not the temps in the coolant...).
But your description sounds more like electrical issues... Take the car to an electric expert, it's really hard to diagnose from far away... "Should" not be head gasket if that only happens when the defroster is on.

04CivicTrouble

thank you both for your insight into my problem. just a quick note that i did verify that the fan is kicking on when turning on the AC.

interestingly enough, when I took a closer look, the area under the lower radiator hose is a little wet with coolant. i do not suspect the hose is loose or the clamp is bad because it wasn't a lot of fluid. i'm wondering if the service station i used installed the thermometer upside down or if the gasket isn't completing the seal. i'm going to take it back and see if they are willing to take a look to see if that's the problem (or at least part of it).

before i do that i'm going to stop by the local auto parts store to see if they will use their OOB for some diagnostics to see if i get any error codes (or specifically electrical errors like you suggest).

if none of those yield a fix, then my best guess is the heater core is plugged. knowing it's under the dashboard and behind the firewall, means i may just bite the bullet and take it to the dealership.

if you have any additional thoughts then i'd certainly welcome them. Thanks again.

BlueEM2

iTrader: (1)

If it was electrical your heat would work. are your rad hoses pressurized and do you have enough coolant in the rad when you open the cap? (When the car is cold, of course?) It really sounds like an air pocket. Does your heat work when you are driving, or is it cold all the time.

Upside down thermo would do it.

04CivicTrouble

I removed the cap just now (car is cold) and can see the coolant so it looks full. Plus the reservoir is full to the cold line. i'm definitely going to have it bled again to make sure there's no air pocket. though it's odd to mention, after turning on the defroster, the air gets "warm" with the control all the way to the hottest setting but not nearly as hot as it is nominally before this problem began. as i mentioned, this is already when the engine has been run and come up to operating temp (driving around the city). i shut the air off immediately because that's when the temp gauge heads toward the red line.

i'm suspecting the thermostat is installed wrong and/or not seated right with regard to the gasket.

on a final note, just figured getting the OOB diagnostics would be a quick way to make sure there isn't a bad sensor somewhere.

again, i really appreciate your help and insight.

gearbox

iTrader: (95)

does the temp gauge act normally without defrost? do the testing procedure to be sure its not the needle messing up.

04CivicTrouble

thanks for the diagnostics procedure for the instrument cluster. i will give that a shot and see what happens.

just to address your question, yes, the temperature gauge works "normally" until the defrost is turned on. no evidence of the jumping around and then approaching the red line.