Adding electronic heater control valve
 

I’ve been having some issues with my coolant rerouted car getting warmer than I'd like at idle and highway speeds on hot days with the AC on. I suspect that adding some restriction to the coolant return that bypasses the radiator would help cool the car significantly.

Upon researching restrictors in the coolant return I stumbled upon various heater control valves. I found a cheap electronic valve that I’d love to add to the car, I’m just not totally sure how or if it’s reasonable to try it.

The part I was considering is: HV 9506C, it looks like they’ve been on pretty much every Ford from the early 80’s through ~2005. In my head I’m imagining something like the fan output, set 5 degrees below where the fans engage. It should exactly opposite of the thermostat and make for some really great temperature management.

This is where I’m too stupid to know what to do. I should be able to just grab an extra output wire from the MS and run to the sensor, right? Or worst case it seems like I could splice into the cooling fan wiring? Or should I just jam an appropriately sized 3/8ths drive socket in the heatercore hose and call it a day?

Potentially relevant car info:
2000 Miata
Turbo
Coolant Reroute
Brain Built MS3x

I tested restrictor stuff a couple years ago, it's on the forums somewhere Funny how a few years ago, people shutdown discussion on how to improve their cooling systems, now there are several threads on the subject.

Pat, I know you tested the valve approach before, did it actually consistently and repeatedly work?

My understanding has always been if a rerouted car is still running hot then you need more shrouding and/or better radiator, and that restricting the bypassed coolant would hardly make any improvement in maintaining temps.

The cheap ones on eBay are very poor quality and are prone to leaking. Even the oem Ford ones are.

KISS. Try a restrictor first to see if the concept has merit. If the restrictor works and otherwise meets your needs, that's what I would use. The last thing I would do is to transform a nice, innocent Miata into a German car that's out of warranty.

Young whippersnappers reinventing the wheel again. I posted this maybe 10 years ago.

You can use a 4-port oil thermostat on the heater OUTLET, using 2 ports which restrict flow when it is hot. This way if you turn on your heater, the outlet coolant temps drop and the oil t-stat opens. So your heater will work when you turn on the blower.

The oil t-stat should have a setpoint HOTTER than your coolant t-stat. This way when coolant isn't fully warmed up and the coolant t-stat is closed, the oil t-stat is fully open, allowing your heater to work. Also, it will only begin blocking flow after the coolant t-stat is open, so there's no condition where both t-stats are closed, which will cause the water pump to see very little flow.

This setup has been tested... the effect is more noticeable in stop and go traffic than when cruising.

Yes, I posted about it long time ago. I used a valve, and a restrictor, posted results of both here.

I have a german car with a computer controlled thermostat. It sits at 197*F almost ALL the time once it warms up. Highest I've ever seen is 199*F, ever. 99.9% of time it's 197*F, rarely it will drop to 195*F. Maybe when it's 20years old it will break, sure, but while it works it is amazing at keeping the engine at target temperature no matter what ambient temp or use.

^^ LOL. I was actually thinking of you when I said "KISS." ;)

Anyway, I've had (and still have) German cars. That's why I like Miatas so much.

LOL

I like both, miata is way easier to work on though. And cheaper to maintain/fix/upgrade no doubt.

Seems like this may be a failed endeavor, for now at least. The part I bought was wrong. Apparently it uses water temp to cut power, rather than using power to cut flow. I may just end up buying a manual valve with a pull cable, old school. Will report back if I ever figure it out. Appreciate the feedback.

You should not need to do this for cooling.

The car runs at ~200 degrees when driving around. When the AC is on at idle it will climb to 215+ within a couple minutes, at which point I shut the AC off and it drops back down to 200. What should I do to fix it (other than taking out the AC)?

Given my situation, it seems like the radiator is enough to handle cooling. I just assumed that hot day + heavy load (AC on) + low flow (water pump spinning at idle) that too much coolant is bypassing the radiator for the car to maintain 200 degrees. Even the biggest radiator and best ducting in the world isn't enough to keep a car cool if water is just going around the radiator anyway. Restrict flow bypassing radiator, car runs cooler.

I bought this: not as fancy, but it'll be enough to confirm if my problem is fixed. Definitely open to other suggestions though.

My 2001 Tundra has a cable operated heater valve that would do what you are trying to do.

But I really think the problem is going to be that you want a flow of coolant across the passages within the engine to moderate localized hot spots and promote a bit of evenness of temperature from cylinder to cylinder. This is even more necessary as you double or triple the horsepower.

I use air conditioning in this same climate and can say it is not easy. When my car was bone stock it would overheat if left to idle in a hot parking lot for 15 minutes. The blacktop can easily be 140 degrees with the strong UV we have here and the air just above it is quite a bit warmer than the rest of the ambient air.

Please post a bunch of pictures of all of your cooling system from the back side of the radiator and the Plumbing and the bumper mouth and even underneath your car so I can see the differences.

With A/C on, on a super hot day, does it overheat at idle? At 20mph? 60mph?

If at idle, you need better fans or something is wrong with the cooling system.

If at 65 mph, you need better ducting, better radiator, more coolant flow through radiator/less bypassing,

When I had my a/c condenser up front, with a MSM radiator my car would get up to 210-215*F on the interstate at 65-70 mph, 100*F day in Houston with a/c on max. That was with some SPAL super awesome fans running too. I wanted it running cooler, so ended up moving the condenser and redoing all my ducting to fix it. But if I had to keep it up front, I would remove the stock crash structure, tube out the front, and put larger heat exchangers in place with bigger fans.