I've probably brought this on myself. I'm in Georgia, and after going turbo and MS3, I finally sought out this summer to get my A/C working. I got it working, but my water temps were headed towards the 250 mark. Previously ran my cooling fans ganged, and while I was running on the warm side (220ish), once the fans were unganged I wasn't getting enough airflow through the rad at 70mph.

So I went ahead and properly shrouded it. Temps were good throughout the summer, 180-200 with A/C on. But the weather has turned - I took the car off the road for a couple of weeks while I did some work and tonight with a 35f ambient, my water temp maintained 135f at 70mph. Oil was on the low side at 180. When I stopped for 3 minutes, the water temp raised up to 170. I stopped to get gas, and the radiator was warm (but not scalding) - so I believe the 120f is valid.

So - obviously - my shrouding is working pretty well. I've also got a few cooling mods..

m-tuned reroute, 190f tstat, godspeed radiator, radiator shroud and upgraded fans, louvered panel on a low-pressure area of the hood facing the correct way. Should also mention a racing beat type 2 nose, so the mouth is a bit bigger as well. I deleted the hard-pipe water line, blocked off the tstat housing, and proceeded to run a stainless steel hose from the heater core to the lower radiator hose to get a little mixing manifold action going on. So my cooling looks a bit like this -



With this setup, I'm wondering if I'm getting too much flow through the heater core. While driving tonight, I turned the heater on, kept a constant speed, and the water temp didn't really budge - stayed at 135.

So - which strategy should I pursue? Open holes in my radiator shroud? Put a piece of plastic in front of the radiator? Put in a flow limiter - like a toyota heater core valve - on the heater core and start varying flow?

 

What year motor do you have?

What percent coolant are you useing, all, some, a splash?

I have used a piece of ABS plastic and the side of a case of beer as a restrictor plate for the radiator before. I wouldn't go right to cutting or adding holes right away.

 

Pull your thermostat and inspect it. I bet it is stuck open. The rest of your system is essentially functioning as stock so, no, your heater core arrangement is not the problem.

 

Agreed. I don't see how your engine could possibly run cooler than 190F with that setup once up to operating temperature. Something is goofy with your thermostat.

 

94 with 99 head, probably a 70/30 ratio,

I'll check the thermostat - but when I pulled it right before this rigamaroll, it was closed.

My concern is that a 5/8ths hose with no restrictions is enough to "bypass" the thermostat.

 

Which head gasket?

 

either a mazda or felpro MLS, I can't remember which one I went with last time.

I was out and about today, 60 degrees ambient - and the water temp was back up to a respectable 170-ish, oil about 210. I'm going to keep an eye on the temps, see what happens when it dips into the 30's tonight.

 

Get a new thermostat for a couple of bucks amnd see what happens.