Cooling Issue. WTF?
 

Hi- 1990 miata, FM Vodoo II. NewKoyorad radiator. NEw T-stat- New Cap - ( new means 6 months old or less). About 3 weeks ago, one of the cooling lines coming off the turbo failed. Luckily, it failed coming down my block so there was no extended driving with the leak or insufficient coolant. The failure was that the hose tore at the make barb where it attaches to the turbo. I repaired the hose, made sure the hoses were not up against anything hot ( manifold, etc), put some heat shield tape loosely around those hoses, and refilled the radiator, burped it etc.

Car would run hot (i.e temp gauge clearly to the right of center) after using boost on the highway or if the car was sitting on my driveway idleing. At low driving speeds of say 35-40mph, the temp would be fine. I confirmed that my fans are both turning on.

I pulled the thermostate out and the car seems to run somewhat cooler, but it not back to just slightly left of center on the temp gauge, and I do see the temp rise after coming off the parkway.

Prior to the hose failing, the temp was rock steady just left of the center of the temp gauge regardless of how hard I ran/how much boost I use etc.

I am almost out of ideas here. I freak out when the temp gauge starts to move to the left of center. Turning on the Heater or the AC on "hot" bring the temp back to where it belongs in fast order.

Any ideas?

Have you made any upgrades to the cooling system? are you running a stock radiator? re-route? what's your coolant/water mix percentage?

was the system burped after the repair was made?

Hi- yes I burped it. The radiator is an aluminum Koyorad. Weird thing is everything ( temp) was 100% fine for 8-9 months before the before the hose repair even on the hottest day.

Right now I have 100% water in the radiator. No coolant. Is that a problem? Should I go back to 70/30 water/coolant? thanks

100% water is better for cooling than 70:30.

sounds like maybe the system isn't pressurizing.

70:30 i s OK IF you have some kind of anti rust such as water wetter or Prestone antirust.

That's that thing. There seems to be tons of pressure. The top hose is super firm. I am at a loss. MAybe I will drain the system over the weekend, make sure there are no obstructions, etc etc.

70:30 is what mazda reccomends. antifreeze is an anti-rust.

100% water needs 100% distilled + rush inhibitor.

No re-route right? also what's the psi rating of your cap?

16 PSI radiator cap from Flyin miata. No Reroute. Cant understand how it goes from perfect for 8 months to now there is an issue. I will check to see if I have any blockage in any of the hoses this weekend.

I am on the same page as brain, I do beleive you are more than likely losing pressure somewhere. Do you have any coolant smell? I guess it could be your waterpump, but in my experience with cars, when you need a water pump, usually, you know.

Post pics of ducting between mouth and front of radiator.

8 Months ago, it was the end of October, now it's the end of June, your car is starting to see actual heat for the first time, and you're not getting enough air "through" your radiator since cutting the big hole for your new intercooler.

some sort of clog or restriction in the cooling system.
mine was in my radiator, which is probably not your case, but i would replace upper/lower radiator hoses and heater core hoses...
or do the heater core delete

I'm going to guess that either the radiator undertray is gone or you have a blown head gasket.

Wait, left of center is cooler.