Hi all... first post. I've already learned a lot here, but have an issue (maybe two) that popped up recently and was hoping for some insight.
I've owned it for one year, currently has 129,xxx miles, all stock except I've added a coolant filter and a scan gauge II... both because of what I have read here.
Until recently had no indications of problems, in particular temperature. I've paid close attention to that. Delta is consistently 8-9 degrees at highway speeds. Truck is not a daily driver... used on weekends, for long family trips, and occasionally to work when it hasn't been used in a week or two, just to keep it from sitting too much.
Problem 1: A few months ago when the weather was still cold, I noticed on several occasions while driving the coolant temp would drop very low. Temps were normal, oil ~ 198-199, coolant 191-193, and suddenly the coolant temp would dip to 165-170, remain there for a while, and come back up.
I was concerned at first because of the wide difference in oil vs. coolant, then decided since the oil temp was staying rock steady, it probably wasn't a serious issue. My guess was that the thermostat was sticking open at times, and dumping relatively cooler coolant from the radiator into the system, more than it should have. Does this sound reasonable? I bought a new thermostat, but have not had a chance to install it yet. (Was away on business 4 weeks).
Problem 2: Driving two weeks ago, in a suburban area tooling along at ~ 30 mph, stopped at stop sign, then accelerated gently through intersection and up a moderately steep hill. After 150-200 yards of incline, noticed a 'hot' smell, looked at scan gauge, oil was 208, coolant 206, and trans temp was 188. NEVER saw the trans that hot before. The truck was empty except for 3 passengers. Saw a whisp of blue smoke from under the hood which quickly went away. Shut the truck off, waited ~ 20 minutes, checked all fluid levels under the hood, started it up, drove home 20 miles, temps rock steady at about 198-199 oil, 191-192 coolant, and 140-145 trans. Had a repeat of problem 2 last weekend... all was normal until oil went up to 211, coolant about 208, trans about 170, hotter than first time except for tranny.
WTH? Could both problems be related to the thermostat... first sticking open, now sometimes sticking closed leading to overheat? Why did the tranny suddenly get so hot, especially the first time, when the truck had been tooling along almost at idle on level ground? Just the therrmostat, or is my transmission slipping now? When I saw the whisp of smoke, I thought maybe I had sticking brake caliper, but I repacked the front wheel bearings a few months ago, and the brakes were in great shape.
I'm obviously planning to replace the thermostat, and I'll also change the transmission fluid & filter just in case (& because I don't know when it was done), but I wanted to see if anyone thought something else needed looked at while I was in there doing the thermostat.
Thanks in advance!
05 F250 2wd CCSB 129k
TL,DR: Coolant temps drop suddenly in cold weather, then come back up just as quickly // Now oil, coolant & especially tranny temps rising quickly without obvious reason