Bros, why is my daily overheating?
 

The car is running hot in traffic, hotter of course when the AC is on...it was 109*f outside yesterday. My CEL flashes at 220*, the radiator boils water occasionally, but the temp-strip on the top of the rad says it's never been over 220*f.

• The water pump is 2-years old
• I have a CX racing radiator
• Murray 1.3BAR radiator cap
• Fans are sealed with tape to the radiator (temporary)
• 180* old thermostat checks out okay, a new one is in there anyway

If I can make it to September with this ----, I will live.

reroute?

Negative. A stock Miata should be able to handle this heat. It did in previous years.

I suspect that I could be losing water possibly, the calibration could be off on the sensor, or I sabotage.

Are the fans coming on?

If they aren't coming on: Disconnect the fan and wire it directly to a battery. If it spins it's the relay, if it doesn't it's the fan itself. Twice I've had a relay to the fan die, and replaced it at a junkyard for $1. Tons of cars use the same relay.

If the fans and thermostat are working it's most likely a waterpump or headgasket.

Edit: Is this a 1.6? Could be the "Cursed Water Plug"

Fans?

Obstruction?

Our '92 overheated...a lot. The first answer was a big PWR radiator. I later did the reroute and ran a stock automatic radiator and kept the same temps.

Sounds like you've got something else compounding the problem.

Fans come on and feel strong. Condenser and radiator are fairly clean.

When stock cars overheat, they are broken.

Check in this order:
-Low coolant level
-Lack of OEM ducting/shrouding
-Leaks (invisible ones)
-Leaks (big -----off ones)
-Radiator obstruction

When you are sitting at your apartment can you get it to overheat just sitting there? IE does the fan turn on and then not cool it down enough to turn back off?

Radiator fluids fresh? What kind of mix are you running?

Air bubble? Give it a bleed maybe...

With the AC on, yes.

I used magical funnel, was fairly certain of no air.

Just a couple cups of anti-freeze, the rest is distilled water.

Coolant is full
OEM stuff is there.
There could be a phantom leak, but pressure tester says no until the rad cap leaks.
I can see through both the rad and condensor.

All this makes me think the water pump is either not effectively moving water, or there is a leak.

Radiator says (according to "temp-strip") less than 120, but CEL flashes at 120, means the block is hotter than the radiator. I think that points to circulation:

Blockage - foreign matter or air pocket
Pump not working as it should

Check the flow.

Also, radiator will transfer more heat to the atmosphere if you run a 195° thermostat. Assuming there is water flow of course.

220*f

I dumped some dye in there today, I guess I'll go look for the leak when I get home.

Stat sticking closed due to used condom?

Yes to the car over heats, or yes to the fans come on and shut off? If you idle the car with AC off with the hood open, does the driver side fan eventually turn on and then back off? If so what does the temp gauge look like during this?

How many times did you let the fans turn on and off while burping with the funnel? I generally let it go 3 times before I consider it good and then top off and put the cap on.

I think your thermostat is sticking personally.

Its more likely than you think.

It overheats, yes the fans come on and shut off. Not sure on the driver-side fan coming on and off, it may not with the Enhanced MS2. The factory temp gauge never moves but it has clearly boiled over.

I usually cycle it once with the nose in the air if there are no bubbles poping.

I'm going to pressure test again tomorrow to check for leaks.
The old one checked out in a boiling pot, put it back in, then replaced with a new one that checked out. I considered shooting the waterneck to make myself feel better.

Is the stat installed the right way?

It's a pain in the ass, but try running sans stat and see if it still overheats.

You also may have a blockage somewhere in the cooling system causing your issue. Does the coolant look nasty?

Coolant looks crystal clear after flushing. thermostat is installed correctly.

The car should not overheat while idling with the AC on. Either insufficient coolant flow through the radiator, or insufficient fan airflow through the radiator, or crud built up in radiator acting as insulation. Doublecheck that both fans are indeed coming on and that neither is spinning backwards.

Confirmed, both come on and spin the correct direction. I'm guessing the water pump is weak, but I don't know how this is possible.

Or, I have a bad calibration on the sensor and 3 bad radiator caps. 1 is old, one is from China, and the other is from the green car.

So what are the chances your radiator has gone to crap?

Edit: if the thermostat is fine, and coolant is flowing, and the fans are coming on, and you used the Magic Funnel of No-Air-Pocketness, and the fans are actually pulling measurable airflow through the mouth of the car, then seems to me there's lousy heat transfer through the radiator itself. We're about out of variables. Can water pumps go bad other than failing at the bearing and leaking?

The radiator is like 3 weeks old.

hg failure? how hard are the hoses when it is hot?

It does - first fan comes on at 203*F, second fan comes on at 208*F.

I've seen plastic impeller water pumps fail, the blades basically disintegrate and can't pump the fluid enough to properly circulate.

I was re-reading through this post and noticed that you mentioned 110F ambient temps. That's pretty f'in hot.

How are you testing for leaks? My pressure tester goes in place of the rad cap. Then I pump it up till the little gauge says whatever pressure I want to test at and I wait for it to leak down or not. When my HG was leaking, it lost 1 psi over about 2 minutes. It was a very slow leak. Slow enough that I wasn't sure if it was just my fancy all-plastic radiator tester or not. But it was very repeatable.

Got an IR temperature probe? You might remove the fans temporarily and point that probe at the back of your radiator. See if there's any cold spots. It might be a pain since you taped on the fans, but at least you'd be certain the rad was working correctly.

I am not convinced that the stock cooling system can cope with 109*F and A/C.

If everything is perfect, the stock system can keep up, but there's always other issues which will easily take the system past its heat transfer limit. It's already close to the limit due to an inherently bad design. There's no reason not to run a reroute and have more even cylinder temps, and a lower average temp.

As the flow around a cylinder decreases, the deltaT between the cylinder wall and the surrounding coolant decreases, leading to less heat transfer. This can overload the system as it increases in local temps raising average temps. It also later crops up in more serious problems like causing headgasket failure, which is usually later blamed for the original overheating issue.

Most cars don't need reroutes, but all of our cars would benefit from a reroute. Our local heat and humidity can stress a car nearly as much in traffic as FI or track use, and a reroute has been the best solution in my experience.

It did last year and I sat in traffic with 112*f heat.

My water pump is all metal btw.

I'm pressure testing by charging through the rad cap neck. lol

Mine couldn't keep up with A/C with temps in the 110-115 range. The radiator was installed by the previous owner, and appeared somewhat new-ish (I'd guess replaced within the past 1-2 years). I tried sealing the fans to the radiator, water wetter, 80/20 water/coolant ratio, setup ducting so 100% of the airflow went through the condensor + radiator, and it still would creep up to 235+ if I had the A/C on driving 70 mph on the freeway. Turning off the A/C would bring it back down to ~210.
I replaced the radiator with a Mishimoto, and it holds at 210-214 under the same conditions in 110-115 degree ambient temps with the A/C running full blast..

He has a CXRacing radiator which I'm assuming is a thicker all metal unit.

Was there any signs of somone using a stop leak product in the past?

Have you taken the water pump off of this car? I have seen the prop wear the block and or housing enough to let water flow around the pump so to speak. Ya might take a listen to the pump while running to maybe hear a milling machine.

I can't hear anything with my stylish det-cans clipped on to that area. I ran acid through the cooling system to clean it out, hopefully this did the job.

I jacked the nose of the car way up in the air with magical funnel of ultimate success and no air came out. The car idled up, one fan came on and never turned off. Number 2 came on then both turned off. With the AC, it boils over the cap. The cap looks great and physically feels stiffer than the old one. I'm perplexed. I'm guessing a water-pump problem. I need to squeak by until September when I take a week off from work to do the swap and tune the car. I'd do the swap now, but not in this heat.

I had to back my timing down a bit to stop my car from overheating in this weather, I'll advance it back up once ambient temps go below 105F.

This is how I see the sun right now in my miata.
https://www.miataturbo.net/attachmen...ine=1344021346

it's probably the battery. dead cell.

What kind of acid did you use to flush the system? Muratic? Im not sure if thats spelled correctly

My '96 overheated when bone stock with A/C running after heat soaking from idling in a sun baked parking lot for a couple of hours. I have since acquired an IR thermometer and learned that asphalt temps in the summer sun commonly reach 135*F or better at 95-96* ambient. I wonder what yours is.

Radiator flush bottle.

On a related note, I found the problem. My passenger side fan stops working after a few seconds. Now, if only I could find the fan I removed from the turbo car I could make this work.

Pass fan is a/c fan. Only comes on when the ac button is pushed and the fan is on.

I fixed it for you. I think? I think the fan is only on with the compressor.

The timing question is a good one. You should check it just for grins.

Not on my computer. Reverant already said 203 and 208* activation points for each.

Can you hotwire the fan and have it stay on or is it the fan motor itself?

I meant interior fan (blower) Basically when the hvac is on and the button is pushed. But yeah, if he's running a standalone who the hell knows?:giggle:

presumably he's got it set up so the a/c fan comes on with a/c compressor OR when temps are over 208F.

Which I think is how stock fan works.

Can you change the temp to something like 150 to make sure it's coming on when that trigger is reached?

This is why I wired both fans to a big relay and switch. No questions asked. If the switch is up, they're on, if it's down, they're off.

You can buy those cheapo $12(??) ebay slim fans and mount the motor and blade assembly into the stock shroud. That's what I did when one of my motors blew.

I can't tell if your fan is broken or if you're having a software/sensor issue.

The fan says "CLANK CLANK CLANK OHMERGARD I'M BROKED" so I'm fairly certain it's a problem with the fan. Thanks for the tip Curly, I'll keep the shroud for the slim-fans I've had in the garage for 5-years.

New fans sealed to the radiator and it still overheats. ----

I didn't think that one fan would be the issue. It's the flow, man.

Obstruction has moved into the lead.

Did the radiator have any styrofoam supports? Any chance they broke/fragmented and a chunk got into the radiator? This actually happened to me when I replaced the radiator on our pickup years ago, but I was able to get it out with reverse flow from a hose.

No foam in there.

the new fan stays on right?

Yes.

Late to the party. Stop guessing if your rad caps are good or not, I've gotten DOA ones from mazda motorpsorts. Put the cap on and squeeze the upper rad hose, if you can hear/see the coolant flowing into the overflow its no good. You have to squeeze really really hard to make it go in with a good cap, don't know if its even possible though, never made coolant go into the overflow with this method on a good cap.