How to unclog a heater core?

Hey guys, have another question. What's the best way to unclog a heater core? Mine's definitely crudded up from something, so I need to fix it. Any experience with different methods?

Uggh... Hope you don't need to remove it - that can be a serious job. How do you know it's clogged? No heat?

Yeah, no heat but the car's cooling system works 100% otherwise. I've eliminated everything else from the equation.

I looked at the service manual and I have to take the dashboard off to take out the core, which means taking off the steering column, center consoles, pretty much everything but the front seats.

It's a $1,200 job at a dealership for 8 hours of labor, but if there's any way to unclog it I'll do that. I won't be able to fix this until next Winter anyway but I'm bundled up already when I go out to the car so I can deal.

it just occurred to me - you could get a "auxiliary" 12v heater that plugs into the cig lighter in teh meantime. Put "electric car heater 12v lighter" int Google shopping and see the list.

Albertj

I've read reviews on those and they don't work well as a defroster. Might keep my feet warm for the 3 hour drive to college though...that's my biggest issue that wool socks won't even fix. Those work if your feet are moving.

IBx1 wrote:

I've read reviews on those and they don't work well as a defroster. Might keep my feet warm for the 3 hour drive to college though...that's my biggest issue that wool socks won't even fix. Those work if your feet are moving.

that's the point. They don't work as well as the built in heater, so the built in heater is worth fixing. It's just a temprary stopgap.

dat sux. are you sure you cant access the core through the glove box? ON all the Hondas ive had this was doable. if you do access the core,i would get a new one. they are not that expensive and the alu is so thin that any corrosion that might have taken place will have thinned out the alu further. considering the labor involved it dont make sense to "blow" out the old one. but if you do,soak it in a alu safe sediment remover. Get a new one,whatever you cant loosen or blow out will eventually make its way out and further contaminate

I saw most of the heater core assembly when I changed the cabin air filters. Haven't looked at it since but I'll see if I can get it out with the glovebox off. Right now my dashboard has no center console pieces because I just finished painting them pearl white and they're going in tomorrow morning. I'll see if I can get all the mounting points off with just the radio and glovebox off. Service manual makes it seem like such a bigger piece than it is!

Damn. I can't do it myself. The evaporator is in the heater assembly, which means I need to disconnect the A/C system too. It's pretty much illegal to own refrigerant and I definitely do not have the tools to recharge that system once I open it up.

I'm getting weary of chemical flushes because there's a good chance it won't work, and then there's a good chance that it won't get completely rinsed out and it'll start to corrode gaskets and hoses. For now I'll grab one of those heaters for my feet and talk to the mechanic who worked on my Riviera sometime far down the line. Good news is the heater cores only cost around $200 shipped.

Thanks for all your quick feedback guys, this is why RivPerformance is still my homepage.

I don't think it's illegal to own refrigerant. Newer cars use R134a, which you buy in cans at Autozone for recharge.

Ilan, I hope you understand the PITA you're about to dive in to. Being a mechanic, I don't even want to do stuff like this. I looked it up, it's a 7.3 hour job (or so it pays). The heater core is inside the heater box, which must also be removed (after the dashboard) and disassembled to access the core i.e. you will see nothing but steel bulkhead, that's how much of the interior needs to be removed. The A/C needs to be evacuated, the Evaporator core needs to be removed, some of the engine compartment needs to be disassembled to gain access to bolts......etc etc. This repair is not something most people can do in their garage.

I strongly recommend having the BCM scanned for A/C faults/codes before you dive in. This will eliminate an electrical part failure. Your Civic has quite a few heater controllers and valves.

I just don't want you to get your car apart in the garage and freeze your balls off for a week trying to fix it......

EDIT: you posted while I was typing this....

Thanks Scott, it's definitely a lot more work than anyone without training can handle. I've eliminated everything else from the equation, and the single valve that opens coolant flow to the heater core works perfectly. The blend motor is fine, and that's about as complicated as my heater system gets.

For now, case closed. Time to save up some serious cash. I was just hoping this would be something I could do, after installing my radio and painting the dash, and doing a good deal of the work(solid rust between cat and midpipe) for the catback on my own.

YYYappp!! gone are the good ol days of working on the Riv with tons of room to spare....they just dont make hands in America like they do in Japan>>>>>

Haha, I had just as much room to work on the Riv! This car isn't that bad as far as work space goes, actually, but it's a bitch to take any interior apart.

And an INSANE bitch to have to bust open the refrigerant system to replace a friggin' heater core!!

Now, we have to be careful with pressure, but have you thought about using a garden hose and/or compressed air to clear out the core with the heater hoses disconnected?? (In the olden days, we used to have a "flushing gun" that combined the two, but parts were also built better then...)

Oh yeah, you can get to the heater core hoses no problem. I can't flush until the spring though, or else the hose and the pipes in our basement leading to it will freeze and break. I had the cooling system, and then the heater core itself, flushed out before but they didn't use any chemical rinse. I think that is my only hope with the heater core, but I'm a bit weary of the after-effects. If it'll cause $800 in gasket and hose damage down the line, and I do plan to keep this car until I get my Master's in 4-1/2 years, that's no good to me either.

IBx1 wrote:

I had the cooling system, and then the heater core itself, flushed out before but they didn't use any chemical rinse.....

If they actually did flush the heater core, with no comments, then I should think that water has to be flowing...

It must've not been opened up enough. Who knows...the car runs fine and doesn't overheat or anything, so at least that's good!

OK, back to basics: Have you felt the temperature of the inlet and outlet hoses from the core?

have you considered back-flushing the heater core ?

before spending over a grand, find a place where you can use a garden hose (NOT a high pressure hose). Disconnect the heater core hoses and run water backwards through the core hoses until it comes out clear. Once it's clear, change hoses until the water comes out clear again. Repeat a few times. This should fix your problem with minimal time and tools. You could also remove the overflow tank and clean the inside if it looks skanky.

I'm guessing your symptom is low/no heat ?

Erm, no. I've checked the heater control valve, I've kept trying to bleed the system of any air, I've had the thermostat replaced at first(blew a good $150...damn) and I've checked everything else. The coolant didn't look good when it was flushed so my best guess is that a previous owner used non-Honda coolant which is corrosive to the system, or just neglected the entire cooling system, the coolant got fouled and voila. No oil in the coolant so my gaskets are fine, but the stuff looked like mud when it should be green.

Jason, the place that flushed it did it forwards and backwards multiple times until it was clear going through. Symptom is no heat until higher revs, so I can keep it at 4k and get heat.

how long ago did you have it done ?
In your position, I'd do a coolant flush, remove the overflow tank and clean it VERY well (you can use a pressure washer in the overflow tank) and backflush the core again. The water will come out cruddy. It should get you at LEAST through the winter.

I had the flush done in early December I believe. Once it's Spring I'll do a flush myself, but the overflow tank looks nice and clean.

Did it restore the heat temporarily and degrade or did you see no improvement ?
I have had much better success backflushing heater cores than with chemical flushes. Heat in the winter, based on your location, should be of immediate concern to you. It's not something you should put off until spring.

I had really good heat right after the service, ok heat that night, and then 3 days later it went back to just a little better than before. I can deal with the cold for this winter, but come spring I'll be able to work on the car more. I don't have a garage and I can't freeze up our hose or pipes.