Improved coolant reroute
 

I bought an off the shelf M-tuned coolant reroute and did a little custom fab to improve it. The original reroute relies on the 2mm hole in the thermostat to flow warm coolant over it before it opens. This never sat well with me since that's pretty much a static column of water from the back of the motor to the relocated T-stat.

Quickie fab/modification to the M-tuned T-stat housing:

http://i425.photobucket.com/albums/p...k.jpg~original

http://i425.photobucket.com/albums/p...q.jpg~original

The hot water flows directly over (or against) the T-stat before returning to the heater core as compared to before where the water pretty much bypassed the T-stat entirely and relied on convection/system heat soak to trigger the T-Stat.

Teach me. I don't understand why a static column is bad. If it's not up to temp, then.?

The hole is to let air through so you can bleed the cooling system. Convection takes care of opening the thermostat.

Ummm, water doesn't enter there in the back of the engine....and its the water pump inlet on the side of the engine.

This will still work, but you have the flow path backwards.

I was confused, when comparing my other knowledge.

He's a little confused too

Every time I have a brilliant idea, I do the research to make sure it's not something someone else already considered. 9 out of 10 times, someone has

In this case, I think aidan is right

I'm always right.

It will work, but not for the reason you think it will.

you probably could have put more holes in the t-stat

it will just have to make a 270* turn
still better than the stupid begi "racer re-route"

Yeah. Heater flow might be compromised.

Yeah... The one I worked with, I just drilled a couple more holes in the thermostat. Heater outlet is blocked. No heater core in the car.

He is thinking the direction of flow backwards, but the concept is sound and should work well. Hot coolant will travel from the head, through the large hose, then out the small one to the heater. Thus hot coolant (when the engine warms) will cause he TStat to open and send some / most / of the hot coolant to the radiator, while some portion continues through the heater core and on to the mixing manifold.

I'd be more worried about loosing flow to the heater core because of the angle.

Assuming the hose attached to the welded fitting goes to the heater core (which is what I assume the OP meant by "back of the engine," then this is a good thing. It corrects the one minor design flaw in the M-tuned hardware, and makes it functionally equivalent to the traditional DIY reroute using the spacer and the Kia water neck.

every time i read a thread with this same title im never disappointed.

Then you must not know how a miata cooling system works. I expected more from you, Mr. know it all.

Thermostats have notches in the sealing flange to prevent a static columb, cook one in a pot of water and you'll see what I mean. I wouldn't even rip the air bleed float pin out and certainly no extra holes, because that's what kills heater core action.

and what happens when there is too much flow to the heater core?

When the thermostat is open. Not close.

No such thing as too much heater flow

Oh.

Well, 99.9% of coolant reroutes work just fine with a heater core at right angle because the heater core is low pressure compared to the block, thermostat open or not.

im not sold on that statement. fwiw ford sells heater core restirctors. iv personally blown out 2 heater cores until i drilled holes into my t-stat

Then you've lifted the head and the rest of your coolant system is shit and inoperable, mainly the overflow and cap.

Or you bought a ford, you should not do that.

^lol ok

No holes in thermostat, heater core intact.

I have yet to explode a heater core. Ever. In my life. I've never drilled a single thermostat.

he was racing dom for his pink
blew the welds on the heater core

I have no idea how fords work, but the pressure in the miata heater core should be about neutral at all times. In stock form it's set up to shunt 100% of the available flow from the water pump.

Therefore, the only way it could ever pop would be pressure, not volume which would best be controlled by a restriction on the inlet. In fact, doing so would place a restriction on the water pump and increase pressure or cause cavitation from unnecessary inlet vacuum whenever the thermostat were closed.

Ergo, if it pops other components of your coolant system failed or you built a shitty cooling loop. Pretty sad really, because it's so fucking easy.

lol

The heater core is not as effective at removing heat as the radiator.

FWIW i run a thermostat in the heater core line just after the heater core. As coolant exiting the heater core exceeds 160 F it starts shutting flow through the heater core down. At 180 F it shuts about 95% of the flow through the heater core off sending more flow to the radiator.

So like a reverse thermostat?

Google bypass style thermostats.

https://cimg7.ibsrv.net/gimg/www.mia...b964dfcb3f.jpg

It's a remote oil cooler thermostat. I changed the wax plug in it to a much lower temp value and plumbed it to operate like that.

My car has nothing coming out of the front of the head and its a begi style reroute so when its cold i only have coolant going through the heater core and through the oil cooler. All i know is that drilling the hole fixed my problem. The heater core was the only thing letting go the rest of the cooling system was new and functional.

Also all the m-tuned/rebranded reroutes iv installed had removed giggle pins with the holes enlarged.

The Miata water pump is not so much a positive displacement pump it will churn away like crazy and not build much pressure even if the system is fully blocked. I don't buy that as what cured your problem. Guys that enlarge the bypass hole are usually doing so because they don't have a heater core circuit for flow to bypass at all and it reduces the rate of temp rise.

The only way you are going to pop stuff is either from thermal mechanical fatigue with too many heat/pressure cycles or you over pressurize the system which generally happens with a head gasket or head issues.

Pulled the figure from 949's site for the standard M-tuned routing schematic

http://i425.photobucket.com/albums/p...f.jpg~original

And revised it to show the change I made to the system using the green line. So the water in the section of hose from the back of the head to the T-stat is no longer static, which means the T-stat directly sees the temperature of the water as it comes out of the motor.

http://i425.photobucket.com/albums/p...k.jpg~original

Going back to the first page - the static column of water is not ideal because it takes a while for convection to do it's job as compared to flowing directly over the T-stat. I'd rather that T-Stat open as soon as the water is up to temp rather than letting it spike over temp (inside the motor) until the hose column heat soaks and triggers the T-stat, only cooling back down after that point.

The size of the hose isn't changing; only the location of the outlet so I would not expect any increase in pressure or volume to the heater core beyond what it is already seeing with the standard coolant reroute.

Since others have been muddying the thread with tangential discussion, I'll re-state that your logic and execution are both sound.


This business of "increased pressure on the heater core" makes little sense. The heater core is already being exposed to a pressure differential of around 14 PSI (or whatever the venting pressure of the radiator cap is), and there's unlikely to be more than a pound of difference (if even that) placed across it by the flow of whatever trivial volume of water that tiny little impeller in the coolant pump is producing*. And, at any rate, said flow will be roughly comparable regardless of the relative locations of the thermostat and the heater core inlet/outlet, for any reasonably sane cooling-system configuration. (eg: one which has a thermostat, a bypass, a mixing manifold, etc.)


* = I can't seem to find any sources here which tell me typical flowrates through or differential pressures across heater cores in automotive cooling systems. If anyone knows of data, I'd be curious to see it.

Yes. your modification was correct. Your original explanation was either confusing or incorrect.

Sound logic themostat will be a little more responsive.

While I agree that the new coolant path is theoretically better, I have the as-shipped M-tuned reroute on my car and it works fine. There's no apparent delay in opening the thermostat, if there were then datalogs would show the coolant temp spiking above the thermostat temperature before dropping back to where it's supposed to be, and they don't. So sure, it's theoretically better, but I don't think it's worth the hassle of modding the remote thermostat housing.

--Ian

JKav seems to have thought it was a solid idea worth mentioning...

https://www.miataturbo.net/engine-pe...4/#post1069438

Having said that, while I agree with Jason that it is a 'bodge' it does seem to work.

:dunno: