22re runs hot after head gasket and multiple thermostats
91 toyota p/u, 22re, base model. i just did a head gasket, timing chain and guides, waterpump, t-stat, radiator, and all coolant hoses except the heater hoses. fired it up, set the timing, adjusted the idle, ran it up to temp, started overheating, shut it down, checked some stuff out. long story short, napa gave me a 195 degree thermostat, which is too hot, so i got a OEM stat from rodland, and it still overheated. not while sitting in the shop idling, but when i took it on a test drive. so i brought it back to the shop, got a 180 from napa, threw that in, ran it up in the shop, temp was perfect, the stat popped at exactly half a gauge and stabilized at about 3/8 gauge. test drove it, temp stayed steady at about a quarter gauge, which was lower than i expected, but i called it good and sent it home on friday. monday the customer called, said it was overheating and had a surging idle. so i had him bring it back in, and did some more testing. radiator has good flow, no cooling system leaks, runs at 1/4 gauge sittin in the shop and 1/8 gauge on the road test with no thermostat in it. i reinstalled the original 190 t-stat that i pulled out on my initial teardown, it doesnt overheat in the shop, but it fluctuated for probably about 45-60 minutes between 3/4 and 1/4 gauge, it finally stabilized at about 3/8 gauge. i havent had a chance to test drive it yet, but thats first on my list for tomorrow. every single t-stat i put in this thing acts like its lazy.
additional info: the truck currently idles at about 1200rpm, diagnostics lead me to a bad auxiliary air valve. i currently have the passage in the throttle body plugged so that i can get the idle down to where it needs to be (750-800). i also did this exact same repair, minus the radiator and a couple of hoses, to my personal vehicle (86 toy p/u, 22re, sr5 4x4). i ended up putting a 180 degree stat in it, and it runs perfect, never overheats, gauge just south of half.
anyone got any ideas? if i cant get to the bottom of this by the end of the day tomorrow, i'm gonna rip the head back off and start from scratch. this truck hase been a nightmare for me, i have never had so many issues working on a 22re.