Hello
So recently, as the weather has begun to get colder, I've needed my heater in my EG civic. No heat. Then I noticed that at idle my RPMS would slightly go up and down, mostly when the engine was just begging to warm up. Once I had driven for a good 15 mins. the RPMS will rarely vary, and I get a little heat -- but even at max it's only lukewarm at best.

I've tried bleeding air from the coolant system with the little bleeder screw as well as adding coolant to the resevoir tank to suck out some air. The first time I did this I had heat and no noticable RPM changes for a couple days, then it reverted to little or no heat and RPM variances again.

I'm not sure what to try now, a new thermostat?
Any help is greatly appreciated!

 

It really sounds to me like you still have some air in the system.

When you bled it, did you do it with the heater on full blast? You should have the heater on when bleeding so the coolant circulates through there too. If you have no heat or intermittent heat, it's because you don't have warm coolant circulating in the heater core for whatever reason... either because the heater core is clogged, or because there's air. Since you've already been fighting air in the system, that's where I'd continue working.

Besides, if the problem went away for awhile when you poured more coolant in, that says to me that it momentarily pushed some hot coolant through the heater core, then stopped.

Also, a hunting idle is another classic case of this, because the idle on Civics is controlled by coolant temp. If it's intermittently getting coolant to the IACV, then you'll have an intermittently moving idle.

You could try a thermostat, but I seriously doubt that's it unless you're noticing the car running overly cold or overly warm. With air in the coolant, the car will very often run within operating temp, but you'll get weird problems like you're noticing.

 

quick way to check if its the thermostat is to let the car run and check the radiator hoses...if the upper is hot and the lower is cold its the thermostat...btw make sure the car has been running for a bit before you check

 

good tip\

 

I did have the heater on full blast but I will try it again. Thanks for the help guys

 

Alright, I've tried everything you guys told me.

-With the heater on full blast I bled air until coolant was pissing out.
-I checked the upper and lower rad hoses -- both were hot.
-The 2 smaller hoses going in and out of the heater itself, though... The one on the left (looking from the front of the car) was hot, and the one on the right was warm, but not nearly as hot.
-I just did all this and while there was no hunting idle at the time, sometimes it does that and sometimes it doesn't, so I'll have to drive it some more to find out if that is continuing to happen as well.
-In either case, I'm still not getting heat.

Again, any help is greatly appreciated.

 

Is the heater valve on the firewall stuck closed?

 

i have a simular problem, but my situation is that the car will get up to normal temp at idle and in town driving, and the heat is nice and hot. once im on the freeway the engine temp drops all the way and my heater is blowing cold.
I think my situation is caused by a 3 core aluminum radiator i installed when the stock radiator cracked.

for your problem i think RonJ is right about the heater valve either being stuck closed or it could be clogged with corrosion.

 

I'll check that, thanks.

 

My issue is like Group Tenacity's.....I also have a three core aluminum radiator but in combination with a mugen thermostat that opens colder than normal, my fan is set to go on at a cooler temp., and I have the redline radiator additive....my heat gets hot early on the drive, then it blows cold after

 

I'm shaking my head here... but why don't you try blocking the radiator. A thick piece of cardboard would do.

 

im not at all complaining by any means though.....i have that setup for cooling the engine rather than blowing heat in my face. its not a dd, rather a beast of a street car.