thirdgenbird

obviously an 80 degree thermostat is going to be open at 80 degrees but how far open?

after repeated testing, my thermostat is only open about the with on a nickel while in a pot of 80 degree water. it looks to me that it has to get between 95-100 degrees to be fully open. (tested with a harbor freight pyrometer)

would this cause my gauge reading and fans to cycle constantly when the car is driven in town or idling?

austin944

Dunno, but I always two of them side-by-side in the same pot of water, new and old generally. It's unlikely they'll both be defective.

The gauge and fans are supposed to cycle when there's little to no air flow through the radiator. What exactly were you expecting and what do you get?

thirdgenbird

I'm not sure it is suposed to cycle as fast as it does.

When I stop at a red light the gauge will cycle between 85 and 100 degrees in less than a minute. The bottom radiator hose will also stay noticably cooler than the upper hose untill after the fans kick on at roughly 90 degrees. Shouldn't the thermostat open to let the radiator cool the car before the fans come on?

The car doesn't overheat but it runs hot enough that the fans run more often than not (regardless of the ambient temp)

Lizard944

There are definately some bad ones out there right out of the box. I tested mine before installing and it wasn't opening until about 208F and was closing way too early. I installed it anyway not putting much faith in the numbers and sure enough it was always running hot, even on cool days on the highway. Put the old one back in and it ran perfectly again. BTW, it was a Genuine Porsche part from the dealership. There might be some bad stock sitting on the shelves.

thirdgenbird

do you know when the original one opened completely?

Lizard944

The old one I was replacing was fully open at ~180F (82C) and closed at ~160F. I was just replacing it as a matter of routine maintenance.

thirdgenbird

thanks for the info. sounds like mine may in fact be the source of my restriction.

i fully plan to replace the t-stat. the question is do i order a radiator and a t-stat.

smokin_944

Thirdgenbird, just curious, what thermal fan switch are you using? 65/60*, 75/70*, 82/77*, or 92/87*? I agree with Lizard944 that your thermostat should be open at whatever the set point is. I always precheck the new therm cause its a PITA changing it if it doesn't work properly.

thirdgenbird

i would assume the car is fitted with the stock thermo switch. from what i can tell the fans run per the clarks garage page. the driver side fan runs @ ~90 and then both fans kick on high at ~100 (based on stock gauge) this leads me to believe i have a 92/102 switch

would i be best off with a lower temp unit. what would you recommend? 87/92 with an 80 degree thermostat?

the car is in the midwest but is rarely used in temps below 40 degrees F and the high for the next 3 days is in the 90s (F) average ambient temps of operation range from 70-90 degrees F

thirdgenbird

anyone? i would like t order parts tomorrow.

thirdgenbird

Ordered an 80 degree t-stat and 92/87 switch per paragons advice.

They agree my t-stat seems to be opening too slow.