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Discussion Starter · #1 ·
Hey guys, my thermostat was stuck open so I replaced it with a stock 195. Opened the bleeder screw while filling it. Closed it when coolant came out. Ran the engine till it came to temp, and thermostat opened. Drove this morning to school and it was consistently fluctuating between 190-196 every minute or so. I'm assuming I need to bleed it again. Thanks it advance
 

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Discussion Starter · #2 · (Edited)
Update: I went to rebleed the system and noticed one of the seals on the radiator cap was torn. When you squeezed the upper rad hose, you could hear the coolant going into the reservoir. I replaced it with 16 lb duralast (that's all they had) and rebleed it. Definitely no air in the system. Temps are steady at idle, reading normal, but when I'm cruising and looking at live data it's just going from 192-198 slowly and very consistently. No overheating or anything. No coolant leaks. The new thermostat was a fail safe 195 from AutoZone. Anyone have any experience with "faulty" aftermarket thermostats doing anything similar? (I will be replacing with AC delco as I prefer to use oem parts. Come to think about it, my last thermostat was not yet a year old when it got stuck open. It was a motorad, who makes the failsafes, i think).
 

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You realize it's not going to perfectly lock the temp at 195, right? The spring will modulate with temperature, and a 5-6deg swing as it does its job is nothing.
 

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Discussion Starter · #4 ·
Yeah, I know. It's just odd. With this car (and any other I've owned), before it'll be steady while cruising. No real noticeable change. At a stop, it'll raise, etc. All dependent on air flow. I've never seen a gauge on any move like this. All while at ~65 mph, within a minute it'll go above the quarter mark and below by a few marks at least twice. It'll do that the whole time while cruising. The reason I'm asking because its a variation in the baseline. I can post a video if that'll help.
 

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It might be the way that new t-stat spring works, possibly acting like an aggressive clutch, very digital when it hits temp to open or close. If you drilled a 1/8" hole or two in the outer flange of the t-stat, it might ease the fluctuations some.
 
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