The solution is to return it to the factory coolant routing. Whether you use the factory pipe that returns coolant to the mixing manifold post-radiator, or return it via rubber hose and a tee to the lower coolant hose that is also post-radiator, is up to you.

At this point, rerouting the rubber hose is an attractive option since it doesn't involve removal of the whole hot side of the engine to get at that mixing manifold. Thanks for the info.

Since the start of this topic I got a different route. I'm implementing a three-way ball valve which will have both hoses and controlling the flow with the valve.

That sounds like a good use of time.

Yossi, do you work in the plumming section of Home Depot?

Not sure if you're cynical or not, but I got everything off eBay. I would definitely try this reroute before spending more money.

Keep factory routing but plumb an oil t-stat into the heater outlet so that when the coolant is cold it's open, and when hot it's closed. That way when you're overheating and you turn on the heater for additional engine cooling, it opens.

I cannot understand why they would ever route the heater return to the top rad hose and expect the engine to warm up at a reasonable rate while getting all that cold water from the radiator.
I am going to use a honda heater valve (nice and compact) with a pull knob in the cabin to block off the coolant flow from the heater core to the mixing manifold (or lower rad hose)for track use, it worked great on my NA oem warmup times and no hot water going back in the engine on track.
https://www.miataturbo.net/attachmen...ine=1384013078
https://www.miataturbo.net/attachmen...ine=1384013078

Exactly, why do people keep screwing with the stock coolant system. I have never seen a single system failure that can be attributed to uneven cooling\heating of the block or cylinders.

The likely hood that there is any real power to be gained is also very very low. As far as I can tell all these re route kits have ever done is cause problems.

Because not everyone are able to spend 600$ for a racing radiator and probably another 600$ for shipping and taxes because I'm not from the US.

What the actual fuck is going on in here??

Keep it fucking stock (with a reroute)! I have a $100 radiator from ebay, a simple $90 reroute spacer, and $12 GM upper radiator hose. Heater core route is essentially stock, and with a 180* thermostat I have great warm up times, heat in the cabin, and an easily controlled engine temp.

WHY ARE THERE VALVES IN YOUR HEATING SYSTEM???

Your coolant rerouting has nothing to do with the heat rejection that your radiator is capable of.

Your engine adds some value of Q (Joules) to your coolant. Your radiator must reject this Q (Joules) to the atmosphere. It doesn't matter what back flips it goes through inbetween, those are the facts. If your radiator is too small, then your radiator is too small.

Further I've been running a Mishimoto "Heavy duty" for like 4 years. It cost 300 bucks. It has a warranty, and is good quality. If you have the money to put a turbo on your car, you probably should be able to afford $300.

The second option is to ream in moderation. Ream for 60 seconds, then let it cool off. If you want maximum ream, then you have to pay maximum dollars.

Ah, no. Mazda is the one that "screwed" with the coolant system when they took the Protege motor and turned it sideways for use in the Miata. Lots of empirical testing shows that good reroutes that return the engine to its original FWD coolant routing (i.e. M-tuned or similar design) improve system efficiency by evening coolant distribution across the four cylinders, resulting in lower coolant temps.

Don't confuse garbage reroutes like the one shown in this thread with the high-quality reroutes that most people build and/or install themselves.

Savington, don't like my DYI re-route? lOL
https://www.miataturbo.net/attachmen...ine=1384027029
https://www.miataturbo.net/attachmen...ine=1384027029

Actually, yours is fine. I'd prefer to see one of our Coolant Blockoff kits instead of the stock water neck on the front of the motor, but to each his own. ;) I was referring to the OP's reroute, which is not ideal (as evidenced by the issues he's having with it). Yours moves the thermostat and main coolant exit to the back of the head, where it belongs, so it's a good improvement over the stock setup. The M-Tuned kits are great because they drop into place with no fabrication required (even for people who still have EGR) and they work as intended, but if you can get the same function with DIY parts and are willing to spend the time to make it work, more power to you.

Trackspeed Coolant Blockoff

M-Tuned Reroute @ Trackspeed

I just like to be able to burp the air out the front of the engine when filling it (seems like there is always a little bit of air traped there) hence the threaded plug on the front but it will probably burp out the back if you break hard a few times when the thermosthat is open or track the car.

The effect of this more even distribution issssss?????????? The difference between you and detonation? Extra cylinder wear? Proof? You guys must be getting pretty damn good with those mega squirts if that is the case.

Thank you, sir. My garbage reroute works just fine. This is the valve in use -

https://www.miataturbo.net/attachmen...ine=1384032185
screen cap

And TravisR, I'm not running a turbo in my car.

If your garbage is working fine don't start threads about this shit.

Maybe start a group buy...

Lower coolant temps, as measured empirically. Any more questions?