Ok so I've been working on the wifes 850 (NA) for the last few weekends and can't figure out whats going on. Day 1 showed up with a leaking radiator and overheating... so I replaced the radiator...
car still overhearts...
so I replace the thermostat....
car starts boiling coolant out of the cap....
Replace cap...
still boiling over....
removed tank and find that the little nipple on the top (that bleeds into the pipe for the thermostat) was clogged up....
Replaced with NEW tank...
car ran fine in my drive way for 45min. no overheating. Drove it all night no problems. Next morning work up and did about an hours drive on it, only to get home to...... you guessed it... empty coolant tank and overheating...
so I figured maybe it finally opened up the thermostat and chugged all the water in blew all the air out... so I fill it up, let the car sit in my driveway again for 30min.... no over heating. Take it for a spin and I get 3 blocks and its overheating....
Now its not Pagging out on the red, its just climbing past the normal spot and gets to right at the red line. Never above it. If I'm driving its fine, I assume the wind cools the motor, but if I sit at a light to long it climbs up...
In the driveway I know the fan is on and keeps the car at temp. But I'm wondering if as I'm driving I might be shorting something in the fan as I cant tell if its on or not...
Not mixing water in the oil... not smoking... did a compression test and everything is even all across. No missfire nothing. car runs fine.
Honestly the under hood temps on my wagon feel hotter than this motor when I pull up (but the wagon is turbo). but what would be causing it to loose fluids? NO visable leaks. Heatercore is bypassed.
TL:DR
car was overheating, Replaced all the cooling system parts, ran fine for a few hours, then started to overheat again. And is boiling fluid over. No signs of headgasket failure. No leaks. WTF would cause it to overheat when driving, but not when sitting in my driveway?





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