Replaced heater core in a 2018

[Top_Fuel]

My 2015 has less heat on the passenger side (measuring air vent temps with a thermometer) but it has leveled off over the last couple of winters. The last "extreme" cold test I ran a few years ago (when it was -4F) the passenger side output barely reached 105F, while the driver side crept up slowly to 130F. The heat output on my car is probably not adequate on the passenger side for extreme cold.

For southern Ohio, my heat is good enough. If I had to keep my wife happy as a passenger in a colder winter climate, I would probably be experimenting with pumping various solutions through the heater core to free up whatever is in there. I can tell you that I'll try anything/everything before I consider replacing the heater core.

The OP having issues with a 2018 is a bit of a head scratcher. Hopefully he can cut his old core open and tell us what it looks like inside.

It's kind of a bummer to hear that the Thermotec heater core may not be a slam dunk solution.

[Fummins]

I wonder if the Canuckistani Mirages have a secret sauce in the coolant to keep us alive in the winter. (Based on my questionable memory of no Canadian core gum-ups.)

I'm not sure, I know that the blue coolant turns thick and sludgy when it leaks from the cvt cooler line. I wonder if humidity is a factor? These things still make heat at -40 but the floor never really warms up.

[MetroMPG]

I haven't actually compared temps between the two sides. It's all about me.

The OP having issues with a 2018 is a bit of a head scratcher. Hopefully he can cut his old core open and tell us what it looks like inside.

Too late!!

I was so tired I tossed it during clean up. Tried to recover it a few hours later dumpster had already been emptied

[DimensionTheory]

I purchased the Thermotec core on eBay, D65003TT. It's entirely possible it got banged up coming from overseas or I simply got one made on a Friday.

In hindsight I do believe that plastic is all simply extra material (USDM models at least) and the better idea would have been to shave the plastic a bit with a Dremel or maybe a knife/razor.. because of my hand, I was having a hell of a time getting those clamps on under the dash, so I thought cutting/flaring the tubes would fix both problems until that pesky steering joint got in the way, and the 5/8 on my flare tool was ever so slightly too small. The core was so close to going in around the joint, possibly a tap from a mallet could have gotten it around but these things are so flimsy I assumed it would just bend it.

I don't like it being repaired this way. It's actually bothering me even though it all seems secure for now. I ordered another Thermotec unit and plan to try again. It'll probably be a few weeks but I'll report back if the new one goes on better. I have heat for now, which was a safety issue with winter setting in. I just need a day off above freezing once the part arrives to go out there again. I can get everything stripped out down there to work in like 10 minutes now, and I have a 5/8 elbow as an emergency core bypass.

I know I never got a temp with a thermometer, or cut the core open but the improvement is insane. The core definitely had an issue with it. My original theory was since I most likely didn't use heat the first 2 years, it may have gummed up. But it seems the Mirage has a constant flow through the core, so I really have no idea what could be the cause, or why some are and some aren't affected. I lived in two places that has particularly dirty air. The overflow tank has a vent hole. It could simply be accumulated dust/pollution getting into the system. I doubt we'll ever really know though unfortunately. It could even come down to just one component having multiple suppliers, and one of their suppliers used something different or had a bad batch and it's luck of the draw from the parts bins.

One last to add. If you practice and practice with those clamps, and the tubes are not obstructed, the job could be done in as little as 30 min (minus refilling and bleeding everything). The clamps themselves could take hours. It's an uncomfortable position even with the seat out but it's not impossible.

[DimensionTheory]

I didn't get a picture of the Thermotec, but this is the factory one before I yanked it.

So as far as the tubes not fitting. The plastic protrusion half circled by red, it was like the straight part of the tube where the screw clamp was, wasn't quite long enough, or the bend wasn't quite 90° enough. It seemed as if no matter what, the flange always sat with about a penny gap (too much for the clips to get around, and I don't believe they really apply a clamping force that would correct that). I'm thinking this plastic should be ok to cut at least half its height off, maybe?

The piece half circled in yellow also caused a problem. With the tube resting to the right of that post like factory it actually angled the longer run of the tube where the screw clamp goes, down about a half inch sorta resting on that plastic tab below and keeping it from getting out of the firewall grommet. I'm pretty sure that post can be cut flush off.

Of course here's to hoping the next Thermotec unit I get fits better and this is all moot!! But to anyone thinking about purchasing one, just be prepared there is a possibility it might need some patient finessing/modifying. A tube bender may also work, I was worried the aluminum would fatigue/break in a spot where I couldn't run an adequate splice and be SOL, so I avoided that route.

[Eggman]

The fleet Mirages have put on millions of miles(combined) over the last 9 years and no heater issues to report, though they never carry passengers.

I wonder if the Canuckistani Mirages have a secret sauce in the coolant to keep us alive in the winter. (Based on my questionable memory of no Canadian core gum-ups.)

I suspect the difference may be that the fleet Mirage doesn't see as many run/stop cycles, meaning when the engine is started, it stays running longer than most. Just speculating...

[Fummins]

I suspect the difference may be that the fleet Mirage doesn't see as many run/stop cycles, meaning when the engine is started, it stays running longer than most. Just speculating...

Good theory but the opossite happens. They see far more run/stop cycles than normal. When engine is started it's shut off at every stop so on average 20-40 start/stops cycles per day.

I do notice that the coolant never turns murky like some of the pics that I've seen from members in the far south, like Florida. I pulled in a car that sat for 3 years and the coolant looked like new. I should pull the heater core out and take a look.


https://mirageforum.com/forum/showth...l=1#post137032

[Top_Fuel]

I purchased the Thermotec core on eBay, D65003TT.

Thanks for the follow-up info...very helpful! Can you post a link to the eBay seller you bought from? It looks like this heater core is available from multiple European countries. Maybe it's the exchange rate or something but the prices (and shipping) seem to be all over the place. If I can get one to my front door for around $100 USD, I may just buy one now and toss it into my Mirage spare parts collection box.

...the better idea would have been to shave the plastic a bit with a Dremel or maybe a knife/razor...

That second set of pics with the colored lines helps. I see what you are saying...definitely seems like cutting the plastic out of the way is the way to go. If you are crazy enough to do this job over again, be sure to post an update.

[DimensionTheory]

Well I got my second Thermotec core in today. It arrived with a flange severely damaged and a tube bent.

Both Thermotec cores came from the same place, Lithuania even though they were from different vendors. I think I paid around $105 each time with Google handling the exchange rate for me. I just chose the fastest listed shipping with a total under $115 each time. First part came in about 8 days, second one was about 5. Customs held the first one up over a weekend in TN.

The packaging is not the best. They put the core in the box only with cardboard covering the faces, then the tubes are bubble wrapped (the light duty stuff) and slid in beside the core. Problem is it's single boxed, and there's not a lot of room. My tubes wound up jammed between the flanges and the box end.

I'm not really sure where I'm going from here on this. I may just be trading this thing in. I've had and built a lot of cars over the years and this is the only one I've ever had where turning a wrench on it feels like some soul-depleting torture chore as opposed weekend hobby fun.

[Top_Fuel]

Thanks for the info. Guess I need to think carefully before I order one. I'd pay extra for someone to double-box it.

...turning a wrench on it feels like some soul-depleting torture chore as opposed weekend hobby fun.

Seems like every heater core job I've ever done has been in that category!