Bypass thermostats are being coming scarce for Fiat spiders. The last one I tried ( a Behr) caused the car to run too cold. Both International and Chris Obert have no idea what the temp rating is for the thermostats they sell. My Fiat parts book lists two bypass thermostats, one rated at 85 degrees C for older fiats and one rated at 90 degrees C for more recent years. The later temp rating is what I need.
I checked Autozone # 25592, on line, per your post, I found Autozone rates them at 192 degrees, which sounds perfect. However, the online info says it does not fit a fiat. Did it fit your fiat without any modifications? If you had to make modifications, what were they.
I have a 1984 Pininfarina, which is fuel injected and needs to run at 190 degrees F.
Yes the mentioned part number is what Autozone quoted me for my 1980 Fiat 124, it was in the stock system, no modifications, same with my 84 Volvo turbo, which also included a water cooled turbo.
The Volvo used another type of bypass system, I'd start the car, back out of the driveway, let the car roll one city block down hill, when I lived in San Francisco and by the end of the block, the needle would just walk right to normal.
The Fiat system is simple, Im shocked its hard to find those parts anymore, the last time I bought one was in 03 and I last looked up the part in 08. The car we did the mod on was a 1986 Toyota MR2, which would take almost 15 minutes to warm up, due to the radiator being in the front and the engine behind the driver. On 38 degree mornings, it would warm up in 2 minutes and give you heat, versus 15 minutes waiting for heat.
The Bypass Thermostat will allow your car to warm up in 45 seconds to 2 minutes. How it works? It connects the upper and lower radiator hoses. The inblock thermostat is removed and the bypass thermostat sits inline on the upper radiaor hose with a "T" connecting the lower radiator hose. When you start the car, water flows around the block via the water pump, The engine heats up completely before the thermostat moves water through the radiator. When the thermostat begins to open it mixes radiator water and prevents shock cooling.
That's no different than the 'bypass' already built in to American engines for decades already. Not to mention hot coolant is normally circulated immediately when the engine starts. Adding a 3rd 'bypass' does nothing.