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PostPosted: June 21, 2018, 8:44 pm 
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OK, so I've just spent two hours looking through TurboMiata.net forums, Miata.net forums, the Mazda manual, and YouTube videos, and I'm more confused then when I started.

I have a 1.6 Miata engine, and the Seven will not have a heater core. I have seen a lot of coolant reroute kit installs, and all of them show the heater core still in use.

Any ideas of how to properly run the coolant to and from the radiator with no heater on a Miata engine???

THANKS IN ADVANCE FOR ANY HELP!

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PostPosted: June 21, 2018, 9:31 pm 
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Hey, you live in Colorado. You need a damn heater 365 days a year!!!!

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PostPosted: June 21, 2018, 9:50 pm 
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Ha - weight, complexity, and I'm putting seat heaters in!

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PostPosted: June 21, 2018, 10:41 pm 
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Joined: January 27, 2010, 1:11 pm
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I did a modified coolant reroute in my build. I removed the neck from the front of the engine and put in a freeze plug. I took I replaced the mixing valve/neck thing on the drivers side of the engine with a modified neck from another car that just has a 1 1/4" connection and a 3/8 barb for the lower radiator and throttle body return back to the engine. On the rear of the engine, I removed the coolant connection and installed the thermostat and cover from the front of the engine on the rear of the head pointing up. I then used a short piece of hose to a SS curved piece that has put a coolant bleed screw/ fill point. From there it goes to another flex hose to a long steel pipe back to the top of the radiator. There is already a small connection on the rear of the engine that goes to the oil cooler and then the throttle body. I kept this as a I wanted some sort of bypass around the thermostat for constant flow.

I have considered adding a swirl tank in place of the SS pipe with fill point to help remove air and give me an easier place to fill as my plug is smaller than any of my funnels so filling the system is difficult. You can see most of the different components in the pics of my build log.

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PostPosted: June 22, 2018, 12:19 am 
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Is the switch on the front of the thermostat housing for a fan? I will figure that out eventually, but thought you guys might know straight away.

Attachment:
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Also, what oil cooler? Does the mix valve on the driver side provide coolant to an oil cooler? This would be the line off the bottom of the mix valve in the photo below?

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What lines do the manifold and throttle body actually need? Those tap off the thermostat housing at the front of the block as well.

I'm thinking I can cap the heater supply at the mix valve and cap the heater supply line from the rear of the block. Correct?

Thanks again!!

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PostPosted: June 22, 2018, 9:31 am 
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In the good ol' days we used to just take the hose that lead to the heater and looped it back to connect to the "back in" connection on the engine. But you also could just block it off.

What makes the Miata any more complicated than that?

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PostPosted: June 22, 2018, 11:42 am 
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carguy123 wrote:
In the good ol' days we used to just take the hose that lead to the heater and looped it back to connect to the "back in" connection on the engine. But you also could just block it off.

What makes the Miata any more complicated than that?


Apparently, it is. turbomiata.net got me thinking it is. I wouldn't dare ask a question on that forum though! You would get eaten alive.

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PostPosted: June 22, 2018, 12:00 pm 
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I know nothing about Miata cooling/heating system.

I would think that IF the Miata controls heater temperature via a blend door and the heater core flow is not modulated, you can simply bypass like carguy suggested.

If the temperature is controlled via coolant flow valve, does it have a bypass function, i.e. 3 hoses or ports on the valve or only 2 hoses/ports? If only 2, then does the valve shut off all flow completely? If so then you should be able to just plug those heater core ports. If 3 ports, then you should be able to bypass, again like carguy said.

If you can find your specific model coolant flow diagram it should be self-evident how to eliminate the heater core.

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PostPosted: June 22, 2018, 4:31 pm 
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You may want to take a look at this page https://www.miata.net/garage/CoolingSystemProblems.html and try a google search on "miata 1.8l coolant flow".
The web page is for an earlier 1.6l engine, but I think it applies. The "G" search has a lot of pictures / diagrams.
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PostPosted: June 22, 2018, 6:16 pm 
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Connecting the two fittings with a hose or capping them with a short piece of hose and a bolt or commercial cap provides an easy option of adding a heater after you drive it.

If you cap/plug the heater fittings, the oil cooler and throttle body idle control coolant circuit will provide a little bit of a bypass for coolant to flow when the thermostat is closed, but to prevent damage, you might consider drilling a 1/8-1/4 hole in the thermostat to ensure adequate flow when cold. If you find it takes longer to warm up, the hole can be soldered and redrilled smaller or just replace the stat.

The oil cooler sandwiches between the oil filter and the block.

When reinstalling the tube under the header, be sure to clean the port in the lower neck well and lube the o ring. Otherwise it will tear.

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PostPosted: June 22, 2018, 7:58 pm 
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I have a 1.6 - thanks for all of the info!

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PostPosted: June 23, 2018, 11:21 pm 
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I replaced my heater core with a one quart Moroso overflow tank. Nice and high on the firewall, acts like a header tank, highest point in the system, so the cylinder head is always full of coolant. My cooing issues all went away after that.
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PostPosted: July 3, 2018, 1:51 pm 
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I've decided to use an overflow tank to make that the highest point in the system for filling. That'll go in place of the heater core.

Another follow up question.

If I am using the Civic radiator that has a cap, is there an issue with two caps in the pressurized system? I figure as long as the overflow tank has a lower pressure cap than the rad, I should be ok. Flawed logic??

Thanks!

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PostPosted: July 3, 2018, 5:49 pm 
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Even if you have a higher pressure cap, it can still seep a bit. Either use two over flows, tee the line, or cap the fitting that will not have an overflow connected and use the highest pressure cap you can find to fit it, though you probably could replace the spring with a spacer. If capping, use a short piece of pressure hose with two fuel line clamps and a bolt shank to plug it. Solder is another option.

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PostPosted: July 3, 2018, 7:03 pm 
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I was still going to take the overpressure line from the overflow tank and bring it to the same on the radiator.

So the routing goes like this (note that this is also a "coolant reroute" for the Miata):

Rear of block spacer with thermosensor and heater line attached - this is before the thermostat. Heater line (5/8) goes to mix manifold on side of block. In this line, a T that goes up to the overflow tank.

After the thermostat, main line to the top of the radiator.

Mix manifold main line to lower radiator tap.

Overpressure line at top of overflow tank to top of radiator overpressure (small line). This part I'm not positive on. Because the tap for the radiator and overflow line are both in case of overpressure, if the overflow reaches 1.1+ bar, the inlet to the radiator would still be closed by the higher pressure cap - correct? So do I run both to small catch cans/can?

Higher pressure cap on radiator, 1.1 bar cap on overflow tank.

As I get it built, I'll try to post some photos of the set up. Again, I appreciate any input!

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