I read one description that this is a huge job, requiring removal of dash, steering wheel, instrument cluster, etc. Is this true? Has anyone done it?

 

Hello friends

To clean the heater core you must:

First Drian all your coolant. Always make sure you do it when engine is cold.

Take both hoses that goes to your heater core out from inside the engine (it useally the upper thiner hose that goes to the back), and with low preasure warm water flush it from one side to see if it comes out the other end. do this a few time.

Take out the termostat and put the termostat housing back without the termostat.

Put all the hoses back to gether and use a coolant flush to add to water and fill up your radiator/ water reservour.

Start the engine and let it run for about 20-30 minutes with the heater on high and fan to full blast. This will run flushing agent all over your system including your heater core.

Shut the engine off and when it's cool, drain all the water again.


After all the water and cleaner is 100% out of your system,
Put the termostat back in it's place.
fill the radiator up again with 50% coolant and 50% DISTILLED water. DO NOT USE NORMAL WATER, normal water can add to your engine corrosion.

Start the car up with heater on full blast and leave the radiator cap off to make sure all the air slowly comes out of your system.

After water level is stable and no more bubble comes up the radiator , you are done.


Good luck my friends

 

They usually are, what is your car specifically, some models are easier than others. Why do you need to replace it? Is it leaking or do you get no heat out of it?

 

Wish I was paying more attention, thanks for the reply! It is a 1990 323.

When we turn on the heater or defrost, we get an antifreeze smell. The windows fog up and the car is almost undriveable. My GF can't say if any heat comes out, the few times she tried it, she turned it off quickly because it only made the window worse.

 

Yep your heater core is toast, I have not replaced a heater core in a Mazda yet (knock on wood) but did on my old Mustang I had, that one I had to rip the whole dash out as well. When you do this make sure you have a vacuum nearby as there is going to be alot of debris from the dash being this old, doesnt hurt to wear a light mask either so you dont breathe it in. Also when you put in the new core its not a bad idea to add a ground wire from the core to the chassis, this will help stop corrosion of the heater core.

 

Started the job today. I am stuck trying to get the instrument cluster out. I assume there are cables behind that need to be detached, but for the life of me, I cannot get to them. It only moves about an inch forward, so can't get to them that way.

Off I go to search google for an answer.

EDIT

I got the cluster off and the dash off.

I was taking off way too many screws, basically I was disassembling the dash, rather than removing it! One I figured that out, I got it our fairly quickly.

Time to remove the heater box and get to the core.

 

I got a 92 and same thing...stinky coolant smell and fog on the window.
I'm debating bypassing the core and using a small ceramic heater that plugs in the cigar lighter...really not looking forward to this at ALL.