I have a 96 850, non-turbo, that I've been using regularly for a few hundred miles each week for a few years with absolutely no major problems. Recently, the radiator went, so I just replaced it about a week ago. Ever since replacing the radiator, I've had some strange behavior:

-engine runs very rough at a cold start
- white smoke comes from tailpipe, and then completely goes away once engine is warmed up
- low coolant light comes on and off while driving, until engine is warmed up, then never comes back on

I've since once had a check engine light after a rough start, and pulled codes p0302 and p0300 (cylinder misfires). For the sudden rough starts, I'm guessing that I need to recheck all the vacuum lines that I had to disconnect when removing the old radiator, or possibly clean the MAF. A couple of years ago I did fix a similar problem with very rough idling, similar codes, by replacing a broken vacuum line going to one of the devices mounted on the fan shroud to the intake.

What I don't understand, and am a little scared of, is why I suddenly have white smoke blowing out the tailpipe, and the red low coolant warning light coming off and on, and then both problems going away after running the engine until it reaches normal operating temperature.

And again, this car was working perfectly fine before replacing the radiator.

Any ideas would be greatly appreciated. Thanks a lot.

 

your original radiator i bet was good but you where losing water right ? white smoke .only 2 things that makes white steam smoke and thats a blown head gasket or cracked head. bluish white -oil smoke.

 

You probably have an issue with the head gasket.
Explains Your problems with the coolant level too.

 

Sounds like the old radiator caused the engine to overheat and ruined your head gasket

Try a leak down test or start the engine cold with the coolant cap off to check for signs of bubbling or something like boiling. If this is the case try and get it fixed asap as you can ruin the head or seize the motor.

 

easy way to check for bad head gasket ....... you need a compressor ....remove each spark plug and load cylinder with air ..... look into radiator and you will see bubbles if you see them bad gasket or cracked head .... now for the head ..... look inbetween the valves real close and see if you can see a hair line crack inbetween the valves try useing a magnifing glass . if you have a crack ..... new head . i'm sure there is a video on this site that shows how to do a head gasket .... if not i'm sure someone here will help you