I was reading threads about the jiggle valve on the thermostat and became curious as to what position mine was installed at. I purchased my 4runner in October and the coolant seamed pretty clean although it was green. The 4runner ran at 195-203 but id say closer to 197-201 in san diego weather since October. I thought this was great because im coming from a lifted xj cherokee which was hard to get to run at 210. I believe the hottest I had seen was 204.8 in Anza Borrego desert 97 degrees out with the a/c on. Anyways, yesterday I replaced the thermostat with a toyota oem unit. The jiggle valve on the thermostat I removed was at 12 o'clock just as i suspected. The strange thing was stamped on the thermostat I believe is a date code "99 3". I would guess this means March 1999, my 4runner is a 99. Is this a original thermostat installed wrong from the factory? I installed the new one, flushed the radiator, block, heater core. Cleaned the overflow tank, refilled the coolant and let it warm up with the heater on. Took a test drive in 80 degree weather with the a/c on in stop an go traffic and sure enough it never went above 192.2 most of the time is was at 190. so that is a pretty solid 8-10 degree drop from before. Im wondering if my 4runner has been running hotter then it should for the past 16 years.
opcorn: Talk of the jiggle valve always causes a lot of stir.