Hi Everyone,


Long time reader first time poster... please be kind (does that sound lame?). I've searched and read a hundred different threads.


I'm running into issues with my coolant temps running hot quickly under moderately aggressive city driving and cannot figure out what the problem is. The build sheet..if you could call it that...is below. If I drive fairly aggressively I'll see temps jump from 205* to 220ish and that's when i limp the car home. Driving slower than my mother i'll slowly see temps creep up to 220. If i coast for a mile or two the temp drops back to 205* range. I'm nearing the end of my patience trying to diagnose this problem and I've thrown more than enough money at the car to keep it cool. Please let me know if there's anything I'm missing or if there is another way i can try to solve this. The car is intended to be a mostly HPDE car that i can cruise around town on the occasional Friday night. I've confirmed the temps that MS is seeing with an independent CLT sensor in the spare QMax port. I was originally hoping my OEM sensor was beginning to fail but no.


Info on the car:

1.6 with MKTurbo full kit installed...MS3, 640cc injectors, etc.

QMax Reroute with included 195* tstat

Supermiata Rad

Both OEM fans spliced to run together. No AC or PS. Fan triggers at OEM temp (208* I believe)

OEM undertray from the mouth of the bumper to the steering rack, sealed fairly well around the intercooler pipes

Spiked Performance hood vents

100% distilled water w/ Water Wetter

Edit: New water pump from TDR installed today. The road test saw 220* still hence why i've given up and come to the experts.

I have a TDR oil cooler kit i'm going to be hopefully installing tomorrow but i don't expect that to be the total fix. The only other thing I can think of is a bad thermostat which i haven't tried yet. I know I have some more ducting to do still but something tells me i shouldn't be this hot with JUST a lack of custom ducting? This setup has a total of MAYBE 30 miles of test and tune on it. If there's anyone in the Dallas Ft Worth area that has any advice or wants to look things over I'm open. Track Dog has been in the loop as I've bought and diagnosed issues and they're stumped as well. All test drives have been in the evening and lately it's been in the 60's in N Dallas so ambient temps are very much in my favor.


Please help!

 

How did you burp the cooling system? Something is definitely off.

If the car is just sitting and idling do both fans turn on and then when temps drop to the point that they turn off?

 

I have the nose of the car about 4ft in the air and i'm squeezing the coolant hoses as it idles to try to agitate any air bubbles out. The fans kick on at the right time and shut off around 200* at idle if i remember correctly. If the car is just sitting at idle it's never a problem.

 

If your CLT temps are spiking and jumping only with load a good bit really fast it could be the broken sensor ground run on the 1.6 cars. That was a huge problem for me, and depending on how you ran the other temperature sensor might effect it as well.

https://www.miataturbo.net/build-thr...7/#post1354392

Otherwise, there's a funny thermostat video a forum member here made a while ago for a reason. They often suck, you should test it before installing it.

 

I saw that awhile back and that's what made me question the thermostat actually. It was a good laugh too. Both the factory and aux sensors are using washers with no thread sealant so grounding shouldnt be an issue per the Qmax instructions. I call it a spike but it's not instant. The climb takes winding out 2nd and part of 3rd which is still not a long time on 12psi. If there's a way to test grounding on the sensors I'm all ears. I'm not too great with electronics but my close friends sure are. Track Dog had mentioned a random issue with coolant sensors and injector duty cycle signal interference where higher RPM (higher duty cycle) was intercepted by the temp gauge as climbing temp. That's part of the reason i installed the aux temp gauge just to verify that wasn't the issue. I may just throw a new tstat in because F it.. i've thrown enough money at the car, what's a little more. The 180* vs 195* is a topic for another thread though. I'm curious if anyone else has suggestions or if i'm lucky come across the same problem and solved it.

 

If you unplug your ECU you should not be able to measure continuity between ground and signal ground. I believe those are pins 1 and 2 for sgnd and pins 14-19 for ground on the MS3 DB37 connector.

 

Right after I watch a YT video to learn how to use my multi meter i'll get onto testing that tomorrow. When I say i'm not good with electronics i mean it's more magic than science to me.

 

That video from around 8 minutes is a good explanation for what happens if the signal ground is mixed with high current return grounds. That would be injectors, idle valve, boost valve, pretty much anything on MS3 since it's all low side drive.

Electricity takes the least resistance, and if that is signal ground it will be so. Passing even small parts of a -2.5A return current for injectors clicking on and off through that ground will cause it to drop a voltage and really mess with voltage divider circuits like coolant sensors.

 

Show a picture of your intercooler mouth.

 

 

Don't judge wiring or cleanliness..... both will be addressed when the car is reliable lol

FWIW: the Intercooler is nearly touching the Rad. From what i've read it's better to have them close so the air keeps passing through rather than becoming turbulent inbetween. The Rad is aluminum taped to the upper support to seal up air beneath the TDR plate

 

That's not as bad I was expecting - but on my brother's car we had the big intercooler that took up the entire mouth that basically blocked the mouth off completely with the IC - similarly, temps of 220 at cruise and then "turning off the a/c" to make sure it didn't overheat sounded familiar. This summer we moved the intercooler back and proceeded to do a much better job sealing up the mouth - along with a built VVT block and reroute. Temps are much more in control now, fans are no longer turning on at speed.

 

Some of my friends are suspecting a dud thermostat so i've ordered the 180* Stant to give that a try. It should open further and sooner to help flow. I'll test the grounds to make sure it's not a contributing factor.

 

There is definitely some simple ducting that can be done, just to plug the sides like where the FMIC inlet and outlet pipes pass through, and in front of those as well.

I hope the T-Stat gives some improvement for you.

 

What setting in your MS are you using for your coolant temp sensor?

 

From the original post: "I've confirmed the temps that MS is seeing with an independent CLT sensor in the spare QMax port. I was originally hoping my OEM sensor was beginning to fail but no."

 

I know...its a long shot, but figured I'd ask.

 

Are you absolutely certain you do not have head / head gasket issues?
The point is, hot gases escaping in the coolant will heat it up pretty quickly.
You can quickly test it by removing the radiator cap, topping up the coolant to the brim, and have someone crank the engine while observing the radiator neck.
If you see bubbles coming up or coolant rushing, you can safely say head gasket is toast or the head is warped.
I prefer doing this test with a hottish/warm engine too, but please do so at your own risk.

Ps# Hope the new thermostat takes care of the problem.

 

Something is definitely off. Im running the same turbo kit as you on my 97 at around 14psi and I have no reroute and a stock rad and my coolant temp has never gone above 201. Im only running the one fan and I live in Georgia where it gets hot as *****.

 

The oversized funnel i've used to burp the coolant had enough extra so you could see what was happening. The car was idling, held at 2k RPM, and revved up and down during the burping process. I stopped when the air bubbles stopped coming out and it stayed that way for a few minutes. Obviously coolant surged in and out of the funnel a little because of the tstat opening more but i'm fairly certain the head and gasket are fine. I'll certainly add it to the list of "double checks" though because this one seems to stump everyone.