How to unclog a heater core?

[quote="IBx1"...the place flushed it forwards and backwards multiple times until it was clear. Symptom is no heat until higher revs, so I can keep it at 4k and get heat.[/quote]

Something doesn't add up here... If they could put water through it a month ago, the damned thing should flow coolant... How about bypassing the valve anyway? Is there any chance of a stat or hose being mis-installed? How about the core hoses being reversed?

(And I assume you've checked the blend-air door with your own eyes, and/or fingers? - Not the bell-crank, the door itself?)

I'll check the blend motor again, since it really is in plain sight and easy to get to, and the heater core already is on an offshoot of the coolant system. Like I said, no overheating problems at all. I'll take a good look at everything today when I'm putting the center console back in.

Quote :

Symptom is no heat until higher revs, so I can keep it at 4k and get heat.

Thermostat missing or stuck open might cause this, or wrong t-stat value. You say the cooling system is working, but is it working too well? Maybe someone swapped out the t-stat for a different one at some point?

The first thing I did was have the dealership install an OEM thermostat. Didn't really help back then either, so the t-stat's fine. It was my first suspicion, since new thermostats are designed to fail open so the car doesn't break for a $30 part.

Could still be stuck open. Might be an easy thing to check. Can you read engine coolant temp with engine warm?

Both coolant lines for the heater core are hot with no big difference between inlet and outlet...I'm gonna check the blend motor again, even though that wouldn't open more as revs get higher, or when the coolant system gets serviced. I'm confused to say the least.

If this turns out to be the blend motor, I'll be relieved and pissed at the same time, although I doubt that's the culprit.

Well, if the core was plugged, one hose should be cold(er)...
And as I mentioned, I wouldn't be surprised if it actually mattered which way the hoses were attached to the core.

Well, I can't get to anything because there's too much stuff in the way, like ECU's and other vital parts. The HVAC has a self-diagnostic procedure which I ran three times and it's code-free so the blend motor is fine. Time to really save up.

....and what about the way the hoses are connected to the core?

They're correct. Inlet goes on top, outlet on the bottom. If you hook them up in reverse, it'll blow all the crap over to the engine and make a bigger problem.

I had a Acura Legend that had a similar problem to yours. I unhooked the heater hoses at the core,and found them to be so clogged with sediment that i wasnt getting any heat.All I had to do was dig out the debris and problem solved. Did you check the hoses that way?

I haven't checked them recently, but I'll take a look. Couldn't hurt to dig anything out if there is anything in the hoses, but I'm just afraid of there being too much crap that I couldn't get out.

IBx1 wrote:

I haven't checked them recently, but I'll take a look. Couldn't hurt to dig anything out if there is anything in the hoses, but I'm just afraid of there being too much crap that I couldn't get out.

Done be skeered! Usually the sediment just bottles up at the connection point.

Okay, fine... Since Rick isn't here lately to comment, I'm going to do it for him (a-hem):

FIND A F@#$^NG HONDA FORUM YOU IDIOT!!!!!!

The comments expressed do not reflect the opinions of the network...

PS - I do think that some cars have crazy piping... just like everything else that isn't "American!"
And, hey! I was going for comedy, anyway....

A heater core works the same on any car. That's why I asked this question here. I wouldn't ask you guys stuff that's expressly specific to my car.

IBx1 wrote:

A heater core works the same on any car. That's why I asked this question here. I wouldn't ask you guys stuff that's expressly specific to my car.

This in theory is true. But each car has peculiarities that can only be addressed by someone experienced with that model. If you take the time to learn and are willing to "dive in" and have a good Haynes manual handy,then you can do all the work yourself. But in the dead of an east coast winter a heated work space really really really is not a bad thing at all!
And if your problem is the heater core that provides heat in thedead of east coast winters,Well ya better get crackin my friend! im jus sayin

http://www.hondacarforum.com/honda-2/13861-2003-honda-civic-heater-not-working-properly.html

...not apparent what they know about this on that Honda forum, have a look.

or this

http://www.justanswer.com/honda/1nxj0-2004-honda-civic-ex-90k-miles-heating-problem-s.html

which basically says the head gasket is wacking out. specifically the honda mechanic says that "...the way Honda engine head gaskets usually fail is, that there is no fluid transfer like oil to water or vise versa. But the combustion starts to bow past the gasket into the cooling system. Eventually, depending on how bad, you either loose heat, or when the pocket gets very large, the coolant stops circulation and the engine overheats."

Sounds a little more like he may know what he is talking about.

Read more: Honda Questions - 2004 Honda Civic EX 90K miles Heating Problem(s) since - JustAnswer http://www.justanswer.com/honda/1nxj0-2004-honda-civic-ex-90k-miles-heating-problem-s.html

...and we won't talk about this article, which points out that the Honda Civic has chronic heater issues:

http://www.autos.com/car-buying/7-honda-civic-problems-every-buyer-needs-to-be-aware-of

Ahem... happy reading.

Albertj

I read somewhere too (on Mitchell Tech Tips) that if the A/C is on (defrost) for too long in the winter, the Evaporator freezes and blocks air flow. I'll assume it blows air.....just cold.

Abaddon wrote:

I read somewhere too (on Mitchell Tech Tips) that if the A/C is on (defrost) for too long in the winter, the Evaporator freezes and blocks air flow. I'll assume it blows air.....just cold.

Technically, unless the engineers fucked up (!), the system cycles the compressor to prevent icing, regardless of the type of system... Now, compared to the other GM systems, our own A/C systems don't normally cycle. They adjust the stroke (the displacement) of the pump to adapt to the requirements... That's why these cars lose no mileage to the pump in mild or cold temps.

Albert, thanks for those articles. The HVAC problems in the last article are not what I'm experiencing where the fan isn't working, and I replaced the thermostat already and that didn't work, but that thing about the head gasket is interesting. I don't know what to hope for in this case, but it shouldn't be as expensive to replace if that's the problem.