Once the engine reaches the temp at which the thermostat should open, ***uming it opens alright, it allows the coolant to flow through the radiator to cool the engine...BUT when does it close? Should it close while the engine is still running? I had some yellow gunky sludge in my 292 and after determining it wasn't coolant mixing with the oil, I began to think it was a low temp thermostat. I semi-confirmed this with the previous owner but he wasn't positive. I ran into some mishaps after putting it all back together (a leak) which prohibit me from testing the hypothesis. I tested the old thermostat on the stove and it started opening right around 180 ish...but I wasn't sure because of the way I had it hanging on a little tie wire hook. I ran it under cold water, dumped out the hot water and started the heating process. The thermostat never closed again to test again, at least not fully. Even when cool to the touch it was still half open (30 mins later). It's been a few hours and it's still cracked a bit. When I removed it from the engine I remember it being fully closed. Is it possible that I messed it up when I ran it under the cold water? Or is it more likely that the thermostat never closed while in the engine, so it ran too cool? Any thoughts? Thanks.
Thermostats are cheap, just buy another one and don't worry about it. I ran one all summer in my truck that didn't close and didn't know it, I thought the temp sender had gone bad (if you'd seen the half-***ed way it was hooked up, you'd know why). Then lo and behold when I need heat, there is none. I took the old one out when it was stone cold, and it was wide open. No sign of yellow gunky stuff when I changed it though.
Yeah, I don't know what the hell is going on with it... I have a new Stant unit in there now (180*), but I need to take it apart again and seal it up so it doesn't leak...I am just trying to theorize (and think wishfully) as to why this gunky **** might have been in the oil. I'm hoping it's thermostat related because I'm kicking myself for even messing with it. I hate antifreeze. The heat in mine blew hot. I got the truck in the early fall and it ran great. Last weekend was the first cold snap we've had (in the 20s) and it's the first time I noticed this yellow sludge- it also hiccuped when starting from a stop even once warmed up. The radiator cap was warm to the touch, but never hot. That was another hint that the thermostat was wrong. The previous owner also thought it was a 160* t-stat. As for the sludge, some thought the truck just hadn't been driven enough. I'm wondering if that was the case. I shouldn't need to put 60 miles on it every time I drive it, though, just for it to get up to temp, though.
Yellow sludge? When was the last time the antifreeze was changed. Probably never! New stat and coolant.
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