wade623

i have started having a problem with the heater when the car is idling the air coming out of the vents gets cold but while driving it gets hot again does anybody have any suggestions on what i should do about it?

pwnsauce

it gets cold? as in is warm then gets cold or starts cold? if it starts cold when u turn the heater on it probly just needs to warm up. you cant turn on your car with a cold engine and just get hot air u gotta let the engine warm up, as with any car.

or the heater cutoff valve is stuck closed. the valve stops hot coolant from going into the heater core when the climate control **** is set to cool. since it is controlled by a vaccum maybe its stuck closed then once you reach higher rpms, while driving, its forced open letting hot coolant into the heater.

wade623

the car will be warm but if im waiting at a light or something like that it will get cold if im sitting still after about a minute it will be blowing cold air and im not sure why its doing this

mac25

...isn't that just because it's cold outside? when you idle for one the fan slows down a bit and secondley your engine isn't making as much heat, so at idle the tempurature of the air coming out of the fan drops.

Gunner

1. Check fluid levels make sure you have proper amount of coolant.

If you are good on that then you may have a vacume leak or your thermostat is stuck wide open.

Another thing it could be is the waterpump.

wade623

the coolant is ok the thermostat is ok ive already looked at that not to long ago
what vacuum lines should i check
i just hope it isnt the water pump

ezone

Possibilities come to mind:

Straight antifreeze, undiluted. Poor heat transfer ability. Should be a 50/50 mix, and test at around -30-40 below zero.

A water pump related problem (impeller fins eroded away, aftermarket water pump, etc.)

An air pocket in the heater core. A couple of things could have happened to cause this: The coolant got low enough to allow air into the heater hoses, or the head gasket is blown, and combustion gases are getting into the heater system. An overheat event could be related to both of these.

ezone

Added because I forgot to select notifications.

wade623

im starting to think that is just some air or maybe a vacuum line it had the head gasket replaced before i bought it so i dont think its that but the guy i bought it from didnt feel like changing the pump i guess so im not sure what that looked like also im not running straight antifreeze
just wondering what is wrong with aftermarket pumps?

pwnsauce

i would just try to get any bubbles out of the lines. if that doesnt fix it maybe do a test for hydrocarbons in the coolant.

as far as the pump goes oem would be the most reliable

Gunner

Loosen your radiator cap and let your car run through 2 fan cycles..dont take it off just loosen it, should get the air out..some people suggest jacking up the front end when you do it as well.

pwnsauce

and make sure your climate control **** is all the way on hot so if theres any bubbles in the heater itll get those out too

Gunner

^^ Thanks forgot to throw that important detail in there...man its early...

pwnsauce

np. most people already know that but whatever lol and yes it is...almost time for bed

04 Honda Civic

iTrader: (2)

Yea its definately air. You recently open the coolant system for some reason?

wade623

i think im just going to be replacing the water pump sems like the most likely cause now.
anything special i should know before i do this?

gearbox

iTrader: (95)

water pumps almost never go bad, and if they did you would know it. if the turbine got stuck, you wouldnt have an engine right now after the timing belt came off. the only real issue waterpumps have is leakage of coolant from the seal. it has a metal turbine that doesnt wear out, and its turned by the belt. if the timing belt is moving, so is the water pump. you are doing all that work for nothing and the problem will not go away.

anibis

It's possible that when the HG went someone tried to put some stop leak junk in and now the heater core is like half clogged and only circulates when you get the rpms (and water pressure) up. Either that or there's an air pocket in the heater core.

1st thing I would do is bleed the system with the car on an incline so the radiator is above the heater core.

2nd thing would be to unhook both heater core hoses and try to flush it out with a hose.

I wouldn't think this would be a water pump issue.

jzawacki

Hi all.. I just registered because I saw this thread and might give some info on what all I have tried with this exact same issue. Right now, after spending $1k+ on the symptoms of this issue, I believe the problem is air in the cooling system. Keep in mind that I have taken the car to many mechanics during this process. Here is what I have researched. (Also, this was for a 2003 Honda Civic LX Sedan, specifically.)

1) Bent/broken fins in the water pump reduce efficiency. My original research indicated that if your water pump has plastic blades, this could be an issue. You'll find, that if you rev the engine to around 2k RPM, you will get heat. This indicates a poor water flow issue. (Replaced the water pump, was good for a day or two, and it was back.)

2) Stuck thermostat. Easy and cheap, replaced it (Still had the problem after a day or two)

3) Radiator cap. Since this is a closed system, if the radiator cap doesn't keep it sealed, it can suck air into the system as well as not allow the fluid back in. (Replaced radiator cap, still had the problem after a day or two).

(Note about the day or two. What it appeared, after each "fix", the coolant system was topped off and "burped". My heat work work great, but once air was re-introduced to the system, which took a day or two, I was back to no heat at idle.)

During all of this, I found that my engine began to overheat at idle. This was due to low coolant. Refilling the coolant would fix the problem, but was only a band-aid to a bigger problem.

4) Now.. for the scary part. Head gasket. In my case, I wasn't blowing water out the exhaust, I didn't notice (Key word, notice) air bubbles in my coolant, but I did come out one day to see my overflow tank hose blown off. My oil wasn't milky. From what I could tell, exhaust was going into the coolant to the point that it would increase the pressure, open the radiator cap (16lbs) and then blow the overflow hose off, which would then spew coolant out of the system, which would lead to air pockets causing this issue again. Quote to have this fixed was like $500 and that was in the case that the head didn't get warped from overheating and would cost even more. After spending the $1k+ already, I didn't want to take the chance of spending another $1k+. So, I purchased a product off the internet. Braced my gas pedal so it would run at 2k RPM so the coolant would stay flowing through everything, and ran it for 1 hour. That was about a year ago. So far, my car has not overheated since and the heat seems to be fine. I don't want to come off like I'm advertising a product, so I'm not going to mention it publicly, but it did work for me. At least, so far. I also understand this isn't a "professional" fix. But, the car is almost 9 years old, and in my opinion, not worth the risk of having it fixed "right".

I'm to the point that I know more about the cooling system in this car than I have EVER wanted to know. Hope something in here helped.

98EKCoupe

I've seen this problem a million times on the D17 engines, almost always ends up being a head gasket. when you replaced the water pump you bled air out of the system and as you drove it exhaust gases would leak into the cooling system creating air pockets causing a loss of heat, reving the engine speeds up the coolant flow and reduces liquid to air heat transfer giving you heat back. I've easily done 100+ head gaskets for this problem

wade623

well is there anything that anybody recomends to clean out the system i was told it sat for a while so ill just try to make sure its clean first before i really do anything else

ezone

Gee, I wonder why a car would "sit for a while"....Hmmmm.....Maybe because it needed a head gasket job? And that costs a lot?

I'll agree, head gaskets are a common problem.

lazlong

1. Check to make sure the the heater core valve is working ok. You can't miss it, just follow the coolant lines and it's right before the lines go into the firewall.

2. Try to bleed the system of air.

3. Check for hydrocarbons in the coolant.

4. If no hydrocarbons, have the coolant system cleaned and flushed.

Or try to unclog the heater core yourself:
[autostream]http://autostream.com/ibcivicforums/?page_type=firebirdplayerthumbnail&framepage=104&t ransactionid=1323837838-71901627&posted_by=lazlong_www.civicforums.com&you tube_video_id=dcL_0TWeZJY[/autostream]

I had the EXACT same problem and it was a clogged heater core.

wade623

ill be trying the heater core thing and ill see what happens with that also he says in the video to use bleach but he uses clr are either of those ok to put in there and will they clean it out?

and you are right about it sitting for a while except the head gasket was replaced along with all of the valves and the timing belt before it was sold

Gunner

I have seen poeple just use water to flush out the system, they have adapters to hook a hose up to..Either way when you do the flush you are still going to have to make sure you get the air out of the system.