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2002 Saab 9-5 Turbo.

I was at a stop sign when the power steering suddenly went out and the engine started smoking. The temperature gauge was normal. I was about a minute from home so I turned around and drove it back home (possibly a bad idea).

The serpentine belt had basically completely crumbled to pieces, as well as the idler pulley. I've replaced both of those parts (power steering is restored) but the engine still smokes.

Blue lines show where the smoke is coming from. It seems to be white/light gray, and it starts smoking after about 10 seconds after turning the car on. I ran it for 1 minute and the amount of smoke stayed steady the whole minute.

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I did a full oil and filter change - the oil looked to be at normal levels on the dip stick, but the drain pan feels lighter than it should so it might have been low. The oil was dirty but did not look milky.

I also checked the coolant but it didn't seem to be lower than usual. Possibly related, this is the same car that had a lot of water dripping from its exhaust (I taste tested and it seemed to be just water)

Any thoughts on the culprit or at least what to try next to diagnose it?

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Your serpentine belt was driving the water pump. When it failed the coolant stopped flowing. The stagnant coolant around the temperature sensor fooled you into thinking the engine was not overheating. It overheated on your way home.

Pull off the black cover over the coil packs. I would bet you will see steam coming from around where the plugs go into the head. You may even see standing water/coolant in the plug recesses. Probably means you have blown your head gasket.

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    Remove the heat shield over the turbo and inspect the engine to find where the water, rather than the water vapor, is coming from. I'm afraid I agree that it's likely the head gasket. Iron block, aluminum head, so overheating is serious and kills many of these cars. In addition to looking under the DI cartridge (which is integral with the coils), I'd also remove the valve cover and see what's in there.
    – jxh
    Commented Jan 24, 2017 at 5:35
  • Do you think the temperature sensor will be accurate now that the new belt is in? Maybe I could turn it on very briefly and see if it starts to climb?
    – purpleACR
    Commented Jan 24, 2017 at 16:57
  • The temperature sensor will work correctly if the water pump is working, but the damage is done. If you warped the head from over heating, then the head needs to removed and at least a new gasket and resurface of the head.
    – enderw88
    Commented Jan 25, 2017 at 12:55
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If as you say engine temps stayed normal then I would guess that this maybe excess coolant or oil that has run along the rocker cover or has ended up trapped in the recesses on the outside of the cylinder head, and this is burning off when it comes into contact with the hotter exhaust port area. Make sure your oil level is good and the coolant system is topped-up and bled properly so that there is no air in the system.. Then leave the vehicle running for a few minutes keeping and eye on the temperatures and see if the smoke starts to diminish. If the smoke continues then I would recommend putting the vehicle up on a ramp and looking from below at the front engine area as I believe there are coolant lines below the exhaust manifold that perhaps have been disturbed or have not been secured/sealed properly during your maintenance work.

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