AE86 Heater core flush


This is a topic I've been dealing with for years now. As of recently (winter 2006) I tried yet again to clean my heater core to get heat out of my red hatchback. This time with much better results.




For the quick run-down, here are the three methods I've tried so far:



- hand pumping a rad flush chemical + CLR through the heater core  (doesn't work very well, not enough pressure/force to really get much out)


- using compressed air to shoot a small amount of water and/rad flush chemical through the heater core (works very well)


- using a pressure washer to simply blast water through the heater core (works pretty well)












For the long stories behind all the procedures, click on the links to go where you need to be...




The Introduction


The First Attempt (the drawn-out, over-thought, and soggy method)


The Continuation


The Second Attempt (the smarter and faster methods)









October 18, 2004 will go down in history as the very first day that I didn't freeze my hiney off once the outside temperature dropped below 5C.  For one moment, the world was a happy place, and I sighed with a big grin.


I've driven my hatchback through three Canadian winters with enough heat to barely melt an ice cube, and as such I can't begin to describe how relieved I am that I won't have to endure that pain again this year. I can't wait to be able to FEEL my fingers while I drive! and my toes...oh god I'll be able to feel MY TOES! Just the thought of the ice not being on the *inside* of the windows is mind boggling!


When I first bought my hatchback in 2001, the coolant was pretty soupy and gross looking. I noticed fairly quickly that the car didn't have any heat, but simply added that to the looooong list of random things that needed tending to. I knew the car was going to be with me for as long as possible, so I didn't worry about it too much.


Then I started to drive around in the fall. Okay...then it started to suck.


At first I thought messing with the heater valve by hand would somehow unclog some obstruction I pictured in my mind. Nope.

Then I thought maybe a simple coolant change would help the heat come back.

Not really.

How about a head gasket change?

haha dream on Corolla boy!


So after all of this, and knowing the history of the car, the problem could only be the result of one thing, a plugged heater core! The part that could be described as the single most difficult to access non-mechanical part in the entire car. Super.


Fast forward two years and here I am, still in disbelief of the -40C winter that just came and went. I planned how I was going to tackle the problem last year, and just now I FINALLY did it.


The First attempt (I seriously suggest you try the second methods first)


If a cooling system isn't maintained, it scums up, plugs up, rusts, decays, etc. Old rubber hoses will actually decay over time and the particulate that is produced by this decay will clog up just about anything it can. If you don't use your heat on a regular basis (allowing coolant to flow through the heater core) in addition to a poorly maintained cooling system, the chances of losing that precious heat in your car increases substantially. In my case, my hatchback was a west coast car. If the heat had been used before I bought it, it was sparingly throughout the winter months if anything.


The only two choices I had were to attempt a chemical flush in hopes of clearing out the plugged core, or replacing it in favour of a new or unclogged unit. A core swap would mean the R&R (remove and replace) of my dash assembly, radio, heater control panel, and heater vents just to access it, not to mention unfastening and refastening the heater hoses in the engine bay, then bleeding the air out of the cooling system afterwards. Considering a chemical flush would mostly involve the last two steps of the first option...I thought it would be worth a try.


I knew that using a product like Gunk's 10-minute rad flush would be a must, but I wasn't sure how to get it in and out of the core without making a big mess. I didn't want to use it as the directions suggested either, by diluting it in water and running it through the entire cooling system. I had so little heat, that if I was going to go through the trouble, I might as well attack the core with all I've got. By luck I came across a hand pump at Canadian Tire (also available at Wal-Mart) which was designed for use with all liquids and or air applications, and it came with the needed hoses as well. Be warned though, this pump is a total piece of crap. It will leak EVERYWHERE so don't be doing any of the following work in your POOMA shoes, you pretty boy.



After finding the right piping adapters and some spare heater hose, I had what I needed to easily pump in, and suck out the corrosive rad cleaner from the heater core. I warmed up the engine to get the core nice and warm (and to further increase the chance of me hurting myself since I seem to be a sadist whenever my toolbox is open) and got to work. A short time later, I had a setup similar shown to the one below. The entire contents of the rad flush plus whatever extra coolant/water was needed to fill the core plus the lines and the pump were in the closed system.



For about 45 minutes, I slowly pumped the fluid in and out of the heater core, swapping the lines halfway through, to reverse the flow of the liquid. The idea behind this closed system was to simply let the chemical work it's way through the core and begin to loosen whatever it was inside.


Next, just for kicks, I tossed in a 1/4 container of CLR I had hiding under the kitchen sink to the mix and I switched to an open system as shown below.



In this setup, I would suck the corrosive mix and pump it right through the core and into another container. At that point, I would pass it through a filter, and repeat the process again...and again...and again. Then I swapped lines, and did it again, and again, and again.


There were two kinds of particulate coming from the core, one looked like small pieces of rusted metal, and the other was what looked like little bits of grey gravel that would smear like a pastel crayon when squeezed.


After I was satisfied that I put in a good fight (and after it got dark, really really cold, and I had come pretty damn close to slipping and killing myself for the 7th time on the giant puddle I was standing in) I took one more step to clean everything out of the heater core. The hand pump was good to circulate the cleaner, but it simply wasn't good enough to apply any real pressure. For this reason, I thought ahead and picked up a rad flushing "tee" which is basically a joint that you put in line of a heater hose which allows for any household outdoor water hose to screw in. Since there's VERY little room to work with behind the engine head where the heater hoses that connect to the core are found, I opted to rig up my own adapter line so I could attach the flushing tee without cutting into my heater hose. See the pic below. Note that aluminum lug nut shanks are perfect heater hose plugs.



With the tee in place, I attached the hose, turned on the water and let it do it's magic. I'm fairly certain that if anything was still loose in that core before hand, it was flushed out with the pressure.


When reinstalling my heater hoses during cleanup, I was sure to refill them and the core as best I could with fresh water to minimize the amount of air stuck in that part of the system. I honestly wouldn't be surprised if half the problem with the heater in my car was due to a small air pocket being trapped in the core.


After it was all said and done, after I got everything connected again, and after I let the air bleed out of the coolant WHILE running the engine at about 3500rpm and opening/closing the heater control valve by hand for around 20 minutes...I was pleasantly greeted by HEAT coming out of the dash vents. Up until that time, the only heat I've ever felt from the car came from the foot setting. I assume this is because that vent is most closely placed to the inlet of the heater core.


Today I drove the car, and for the first time ever I actually had to turn down the heat, and while driving on the highway no less!


When it gets colder outside, I plan on blocking the front of the rad with cardboard or plastic to minimize the air flow through it, and maximize the potential for heat to be transferred only through the heater core which in effect is nothing more than a small radiator. Since I run an electric fan (which is only turned on while in traffic, even in the summer), I don't worry about blocking the radiator since I know that turning it on will be more than enough air flow to keep the car cool. The AE86's cooling system works extremely well when properly maintained, and I have no doubts about running this kind of setup.


I hope this article has helped, having no heat isn't an enjoyable experience, especially if you're delivering pizza like I did one winter ;)




                The Continuation (as posted on Dori-Kaze Feb 3rd, 2007)

Well, my ongoing battle with my heater core is coming closer to an end.

In my last thread about this topic I asked what others might do to clean their heater cores, as mine was obviously plugged with material/decayed hose particulate/crap, and I got a couple ideas from you guys.

The very FIRST thing I did, was replace all my old rotten radiator and heater hoses. Considering they were most likely the cause of my heater core being blocked to begin with (rubber degrades over time), it wouldn't make sense to clean everything out before changing them.

The next plan was to go to a rad shop and have them flush my entire cooling system AND the heater core separately. Considering my working hours however, this is damn near impossible to work into my schedule.


The Second Attempt (The methods you should try first)

Nusneak suggested something else...using compressed air to shoot water through the core...
Well over the period of a few hours one night, that's exactly what I did. I filled the heater core and a narrow hose I had connected to one of the inlets with water, then I would stick an air nozzle into the end of the hose and shoot a burst of air to force all the water through and out of the core.

I repeated that dozens of times.


Here's what came out:




It's easy to understand why I had no heat.

Keep in mind, the only reason why I went through all the trouble to save the crap  that was shot out was for you, the reader, to fully understand just how gummed up heater cores can get. So you better appreciate it!

I got back a lot of heat after doing this, but still not as much as I wanted. It was obvious there was still more gunk inside the core.

The final step I took is something I simply can't believe I didn't do years ago. I stuck the end of a pressure washer gun into one of the heater hoses and blasted water through the core.

Now my heat is probably back up to about 70% of where it should be. It's not incredible, but during those really cold days it still helps a great deal.

Hope this helps all you freezing hachi-owners out!





Dreams of Drifting Copyright 01/2000 Chris Migallo

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