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Flyin Miata coolant reroute

Flyin Miata coolant reroute

Regular price $461.99 USD
Regular price Sale price $461.99 USD
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Option 1
Option 2
Option 3




Fits: 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999, 2000, 2001, 2002, 2003, 2004, 2004 MSM, 2005, 2005 MSM

Emissions: Emissions do not apply.

There are no shipping restrictions on this item.

Warranty: 1 year

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The best coolant reroute on the market - and the only one that is truly compatible with a turbocharger.

First - why do you want a coolant reroute? Because when Mazda went to put the B-series engine in the Miata, they decided to put the thermostat on the front of the engine for packaging reasons. This means that a large portion of the coolant never goes through the back half of the engine, leading to poor overall heat transfer and problems with the #4 cylinder running hot. Moving the thermostat to the back of the engine, where it's supposed to be, solves these problems.

We've been selling reroutes for years, and they've been gradually getting better. This one has been designed and tested for maximum flow. We went through multiple designs testing the flow to make sure this is actually true. Our flow area is 8% better than stock, 11% better than the first reroute we sold and 5% better than our previous offering. We even tested flow through the heater so you'll stay warm.

It puts the thermostat right into the head where it belongs so it reacts quickly. It's completely compatible with EGR pipes - not "it works if you hit it with a hammer" compatible, but done right. It's fully electrically conductive so your temperature sensors read properly, and it has a spot for an aftermarket sensor. The reroute housing is a single piece to avoid leaks. Even the thermostat is an off-the-shelf 195°F unit so you can run a different temperature if you'd like (we sell a 180°F unit but find it's not necessary for most and can cause check engine lights in some cars). There's a bleeder screw on the top of the housing so you're sure you don't have air bubbles. And it includes a bracket to properly secure the upper radiator hose. So it's the best reroute you can buy already.

But the big difference is the turbocharger. We worked with the engineering department at Colorado Mesa University to map out all the cooling factors of the Miata engine, and discovered that a water-cooled turbocharger will increase the temperature of the coolant flowing through it by as much as the rest of the engine put together. To make things worse, this very hot coolant is mixed right back into the engine coolant, with no chance to cool down at all. Obviously, we decided to address this. First, we dropped the amount of flow into the turbo - they're cooled by the engine oil during operation, they really only need the water cooling when the engine is off and they use thermal siphoning to get it. The big difference is the plumbing, though - the water coming from the turbo is now plumbed back into the water heading into the radiator so that it's cooled before going back into the engine.

Choose the NA or NB kit according to the intake manifold that you're using - the only difference between the two kits is the hose bracket, which bolts to the intake manifold.

If you have an upright / stock-style radiator, with the inlet on top toward the middle of the radiator, choose the "upright" option. This will add an adapter hose kit that cleanly routes the coolant to the radiator inlet. Note that you'll still use the included upper radiator hose, you'll just add the adapter hose kit to the standard hose. If you have a crossflow radiator, with the inlet all the way on the side of the radiator, choose "crossflow", as you don't need the adapter hose kit.

Why does the 1994 and the 2001-2005 (NB2) need the upright radiator kit, even if you have a crossflow radiator? For the 1994 (and only the 1994), it has a goofy linkage on the throttle body that will interfere with the radiator hose unless you use the upright radiator adapter. For the NB2, there are AC lines in the way - it works without the adapter, but it's clumsy and could be better. In both cases, with the adapter, it fits well. 

If you are going to be using this reroute with a turbo, our turbo connection kit includes new multi-layer silicone lines with heat shielding, anchors and all fittings. This kit works great with our turbo kits (with our Garrett turbos), as well as Mazdaspeed Miata IHI turbos (on an MSM block or a non-MSM). 

If you don't already have banjo fittings (hose barbs) on your turbo - e.g., you have our old hardline kit - add the banjo fittings above. Note that clicking the box will only add one, you need two. Please be sure to edit your cart. Most people will already have banjo fittings and won't need more.

Built in the US. Includes everything required for installation. Compatible with stock and FM turbo EGR piping. Compatible with both upright and crossflow radiators. Compatible with our Big Spark kit. Includes all required hoses/lines, custom thermostat gasket, and fittings as well as plates to block off either the thermostat or the thermostat neck (at the head) and plugs for unused fittings.

There's a bunch of noise about reroutes and 01-05 head gaskets, thanks to that head gasket having different size passages to manage the coolant flow better with the stock routing. Are they safe? Do you have to use an earlier head gasket? In short, you'll be fine with the stock headgasket - we've had this reroute on our development '02 through thousands of street and track miles with no issues, and we're not the only ones. If you have to swap the head gasket for other reasons, you might as well use the earlier head gasket, but it's not a requirement.  

If you're planning to remove the thermostat / water neck altogether (not required, although we include a block-off plate for it), be sure to add our timing cover hole plate kit to keep your timing belt safe. Refer to the instructions for more info on deleting the thermostat neck. 

Customer Reviews

Based on 19 reviews
Low Quality Cork Gaskets...

Three days of driving. That is what I got after paying a 40+ year old Miata specialist shop to install this system into my NA. My mechanic's first thoughts upon seeing the kit were of surprise. He couldn't believe that a kit costing 400+ dollars would include cork gaskets. I assured him that this kit was from the highly reputable Flyin' Miata, that Donut Media had installed one in their own car; that these parts were to be trusted. The gasket, of course, blew out on my third day going about 30mph. Coolant steamed and gushed all over my engine bay, causing quite a bit of embarrassment for me as I was displaying my "brand new parts" to a close friend. Two $100 tows later, and the situation was resolved. Flyin' Miata staff explained to me that they had moved away from oem style gasket material to cork for... what reason again? Ease on production side as I understand. Credit where it's due: they sent over a new gasket in cork... and later a second and third gasket that I had not requested. My mechanic wouldn't consider touching these, and frankly I don't blame him. We an oem gasket and went from there, no problem. Look, the hardware seems solid, but that really doesn't matter when the system's success hinges on a low quality gasket. I give three stars, because although it blew out almost immediately it hasn't had a problem since... but I can't see shopping here in the future. Customer service is fine, but I really just wanted my money back on the kit and got gaskets. Not the best

We're sorry to hear about your experience here. While we've seen a small number of minor leaks with this gasket, they're typically solved by tightening the mounting bolts. We're currently using this gasket on many personal and shop cars with no issues. As for why we use this instead of an OEM gasket, that's because the OEM gasket needs to be cut to fit and this gasket is perfectly shaped to start off with.

(which we're using for ease of installation, as it doesn't have to be

Wow, what a difference in cooling the engine!

I installed this on my DD as I travel 148 miles round trip to work on my 03 NB mostly stock car. Driving in Texas the last 2 weeks with outside temps near 100 to 102 has be more enjoyable with this reroute kit. Last summer there were several days I could not drive as the engine was going past 230 degrees in city driving and staying in the 212 to 220's. So far it has reached 212 once and it was the first day after installing the FM reroute kit, probably one last air bubble. This past week it never got over 204 in stop and go traffic and on the highway it would run in the high 180's to mid 190's. And that is with the AC on!

Thank you FM for the time you guys have put into making this a great product.

Cooler than the other side of the Pillow

Hopefully this is shorter than my other review. This kit was purchased for a 1990 Miata running a 1993 motor. Was installed by two fat guys, one that was weak as heck due to lingering covid symptoms (both fat guys, had gorilla like hands).

If you can, try to do this mod while the engine is outside, it will save you so much time and struggling. that being said, i dont know how long this install took, but it wasn't taxing in the least. the hardest part was trying to get our gorilla hands behind the blocks for certain steps, but it got done, we did it. we kicked ass. watch the video on the install, super informative, but honestly this install isn't difficult. you'll get it, have patience, have a friend with smaller hands, but youll get them ham hands in the back i promise. take it slow, follow instructions.

How does it perform. My god, you know those too good to be true things you see on tv. this is it. this is too good to be true, while actually being true. fixed all my issues. i can run my car hard, and if i get the temp to hiccup up, my heart skips a beat, i start cursing everyone that has ever wronged me, realize my wife should divorce me, but then i look back down and notice, Madre de Dios, the temp went back to normal. It's the best. the temp never rises to anything worrisome, but i still have ptsd from the before time overheating days. Invest in this kit, watch the video before bed, ket a new under-tray if yours is missing, and get hyped as hell. I think i got the upgraded turbo lines with the kit. but don't hesitate, buy this kit.

Just what's needed!

We had an engine failure due to a bit much boost causing overheating of cylinder 3, so when re-building, we installed this coolant re-routing kit. Car is now producing 327rwhp & no overheating issues on any cylinder- hence - absolutely recommended!

very good kit

I research a lot before ordering. The following are reasons I ordered this:
1.The FM kit is the latest design compared to every other kit on the market.
2. Use of gasket helps to prevent leaks. I haven't had any so far.
3. The coolant ports in case I want to go turbo in the future is a plus.
4. OE size thermostat.
5. FM has the best install video. Actually no one lese has a video period.
6. Used it with a SM Crossflow radiator and hose routing was not a problem.

Lessons I learned:
1. The old gaskets are a pain to remove. The rear one is impossible to see. I used a reflective mirror taped to the firewall so I don't scratch the engine block while slowly use a rotary tool to polish off the old gaskets. It's a 10second job in the video that in my real life took 2 whole days. Have some spring constant clamps on hand at least for the rear main outlet and one of the heater hoses, they are about $5 a piece from Amazon. I don't have enough confidence in the included clamps and would prefer to not have to go back to chase leaks, since it will require removing the EGR and coilpack on my NB1. Ran a few hundred miles and one track day and no leaks.