Here's another question...

With the 37mm Koyo going to/from the race track the coolant temps would stay at around 180 unless it was could outside, then would drop to 160-170 range. I expect to be even lower than that with the TSE radiator on the highway commutes. So my question is, how low is too low? Only concern is doing any damage to the engine.

Also, does anybody have a picture of how to partially block off the radiator to artificially raise coolant temps on the highway if I am to low in temps for comfort? Thanks!

As long as your thermostat is working correctly you should stay at proper operating temperature even if your radiator was the size of the moon.

Isn't the thermostat at a minimum setting at that low of cooling temps, smallest opening? If the car is at 140 degrees on the highway at 70 mph with the thermostat at minimum setting, is that OK?

If the coolant temp is at 140 then the thermostat should be closed and almost no water should be flowing through the radiator.

Several times I have seen cooling system setups that should be good enough to cool the car they are on but they are not. Most every time I have found the problem to be the system is not holding full pressure.

The minutest of pinhole even if it takes a week to measure the coolant loss will cause the system to overheat when you flog on it for a full session at a time and the system pressure drops because of the small hole.

Have to pressure test it when it is cold to find the leak because when it’s hot it vaporizes too fast to find the drip. I made my own pressure tester by cutting up a presta bicycle tube and stuffing the valve in a piece of hose that fits on the overflow tube on the radiator filler neck. Carefully use a bicycle pump to put about 25 psi in the radiator and see if it holds steady pressure for a half hour or so. Don’t put much more than 25psi or you might pop the radiator.

We have found the same thing. All of our cars have coolant pressure warning lights. Crusher has a readout on the dash display. Running a crossflow or multi pass rad reduces the pressure spike the cap sees. Those spikes blow coolant past the cap into the overflow.

I've had the worst issue just getting fucking radiator caps that work. I've been through 3 madza ones and a parts store one before I got one that didnt die after a couple of weeks. On all but the most recent one, once the car is warm you can just gently squeeze the upper rad hose and watch the coolant flow into the overflow. When they're new they dont do that and the one good one in there now doesnt do it either.

If it's an aluminum rad, make sure the filler neck isn't damaged or distorted. Common for them to get tweaked a bit and allow pressure loss even with a new cap. We use the Koyo 1.3bar (19psi) caps and have never had one fail. We damaged the seal on one but that was our fault.

I've seen nearly as many engines killed due to bad caps as bad rads.

Nope, did it on the factory radiator and the new stock replacement from mazdaspeed.

Stant or mystery meat?

The radiator or the caps or the thermostat? Thermostat is the one that came in the car from the factory. Rad would be whatever mazdaspeed sends you when you buy a legal stock radiator for a manual tranny car. And cap would be 3 that came in a box that said mazda on it, from mazda speed, and another the came in a box that said autopart international on it, from autopart international.

Got a picture of how you did this? I know I have a small leak in my setup and have been reluctant to go buy a pressure testing setup from HF because I am not sure if the kit will have a cap that fits my TSE radiator.

Got the radiator installed over the weekend. Cap is really close to where my intercooler piping is routed and will need to be changed but works for now. 1st test is this coming Sunday at ACS. Will report back but am very hopeful. The TSE unit lines up SOO much better with the factory undertray at the bottom, it's awesome.