Brokeback (Matt)
Brokeback (Matt) HalfDork
9/20/20 9:54 p.m.

Hey all, hoping Keith sees this but also wanted general thoughts/experiences. 
 

I bought a 01 Miata about a year ago with 35k miles on it, manual trans and cloth interior but cruise control, power windows etc.  I added a Torsen but otherwise haven't driven it much since then, I was driving my NA but I sold that recently. 
 

This past weekend I drove the car from Flagstaff to LA, which is the first major freeway trip I've done. Biggest issue (besides the speed sensor cutting out, fixed that today hopefully) was overheating on a couple of the longer grades between needles and Barstow, and Barstow and LA. Outside temps were 100-105ish, and I had the AC on which I'm sure didn't help. I saw coolant temp on my ultra-gauge get up to around 230 and I turned off the AC and sorta backed off. This happened at 75mph and also at 50ish while in traffic. 
 

Is this super common? I did change coolant and fluids when I got the car, but water pump radiator etc is all 20 years old at this point. 
 

I ordered a coolant reroute kit, and then did a bit more research and I guess head gaskets are different and the 01 has less coolant flow to the front 2 cylinders which in turn pushes more to the 3/4 cylinders. If I just put the coolant reroute on (and don't change head gaskets cause that sounds like a PITA) am I gonna have more problems with the front 2 cylinders? 
 

Thoughts are welcome, I'm rambling at this point but I'm still surprised a stock vehicle had issues with AC and overheating. 

cmcgregor (Forum Supporter)
cmcgregor (Forum Supporter) SuperDork
9/20/20 9:55 p.m.

Does it have the stock undertray? Those have a tendency to go missing, which can be a problem. 

Brokeback (Matt)
Brokeback (Matt) HalfDork
9/20/20 10:18 p.m.

Yea, stock undertray is still there, although I noticed most of the foam that I assume was there originally between the tray and the bottom of the radiator is now gone, the desert heat took its toll. 

 

OldGray320i (Forum Supporter)
OldGray320i (Forum Supporter) Dork
9/20/20 10:24 p.m.

The stock undertray would help - my car will actually run a little warmer at speed than at idle (super strange to me...).  I need to get one...

I'm in Tucson, so trust me I know about the heat!  My car never ran more than 203 before I changed the water pump, but, I also added a FM timing wheel, and I think I was getting a little detonation, too - but, in the heat with the AC on I was running 220s on the hottest days (at 108 or better ambient, I think 224 was the highest I saw), and mid to high 2-teens at 103/105 ambient temps.

I changed to a 75/25 water/coolant mix, and dropped my temps dramatically - I don't think the car has seen past 207 since then on the few 103/105 days we've had in the last couple weeks.

In Tucson I can get away with that mix, but if you're in Flag, you'd probably want to watch that mix.  I found a chart somewhere that gave freezing points for different mixes - and in colder weather you'd want to run 50/50.

Brokeback (Matt)
Brokeback (Matt) HalfDork
9/21/20 10:10 a.m.
OldGray320i (Forum Supporter) said:

The stock undertray would help - my car will actually run a little warmer at speed than at idle (super strange to me...).  I need to get one...

I'm in Tucson, so trust me I know about the heat!  My car never ran more than 203 before I changed the water pump, but, I also added a FM timing wheel, and I think I was getting a little detonation, too - but, in the heat with the AC on I was running 220s on the hottest days (at 108 or better ambient, I think 224 was the highest I saw), and mid to high 2-teens at 103/105 ambient temps.

I changed to a 75/25 water/coolant mix, and dropped my temps dramatically - I don't think the car has seen past 207 since then on the few 103/105 days we've had in the last couple weeks.

In Tucson I can get away with that mix, but if you're in Flag, you'd probably want to watch that mix.  I found a chart somewhere that gave freezing points for different mixes - and in colder weather you'd want to run 50/50.

OK, that makes me feel a little better about the temps I was seeing then.  I am at 50/50 mix right now but don't particularly want to increase the water and have issues in the winter. I planned on adding an FM Turbo kit but after this, I think I need to do some big cooling upgrades if I want to keep everything in a happy temperature range.  I guess I live in a hot environment (if I drive anywhere outside of Flagstaff at least)

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