Hissing sound and smoke from engine after starting, then car dies

Car started from sitting overnight in freezing temps (single digits) then the hissing sound and smoke appeared as in the video posted, then the car dies out. Car started fine in colder temps all week before.

Any ideas of what it could be? Can’t get hood open right now with cold temperature. The video is under the front of car under radiator area.

2006 Hyundai Sonata
3.3 V6

I don’t know. My guess smoke is from exhaust leak. But I would not think that would prevent engine from running. Do you have a code reader? Was CEL light on previous to this?

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White smoke from under the hood could be a coolant leak, either a burst hose, head gasket, or cracked block. Was the coolant in good shape? If it was diluted it could have frozen, causing all kinds of problems.


I too wondered about coolant, but question it producing that vapor on a cold start.

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It looks like steam to me. If there’s no obvious source (like the radiator cap is missing, coolant hose is split, crack in the radiator … etc … ) my first step would be to verify the coolant is at least a 50/50 mix, and the freeze protection is good to -20 deg F. Folks here in coastal Calif will sometimes take a weekend holiday & drive to the ski resorts and wake up the next am to find their car engine has been damaged by coolant who’s freeze protection was ok at sea level temperatures, but not at 8000 feet winter temperatures. Hopefully that’s not the problem.


Does it smell like rubber? One of the pulleys has seized: alternator, water pump, tensioner pulley, the smoke is from the drive belt. The drag from the seized pulley is causing the engine to stall.


Then what is the hissing sound that continues after the engine has stopped, if it’s a pulley?

Did water freeze inside the exhaust? I have no idea how water would get in there though.

Reach under and squeeze a radiator hose. Is it solid like the water is frozen?

No codes and CEL.

Checked coolant before deep freeze and looked fine.

It is prestone 50/50 mix. Still can’t get hood open to check anything :disappointed:

Did not notice any smells.

Still can’t get hood open. Happens when it’s very cold, next day or so should be above freezing. I tried a portable propane heater near the latch area but nothing.

Don’t think hoses are accessible from underneath but it’s on snow and ice right now and dont want jack up on that.

You might try a hair dryer, pointed upward from under the car. It seems pretty unsafe to introduce anything w/an open flame near the engine compartment, in case you have a gasoline leak for example. Even a hair dryer could be unsafe.

I used a forceps tool similar to below to lay underneath the car & grab hold & pull a stubborn hood-opening cable on my Corolla. Nothing frozen though. It would have been easier if there was a helper working from the driver’s seat end of the cable, opening the closing the latch control.

In any event, once you get the hood opened suggest to take a photo of the latch & cable area so you know what you need to grab hold of from below if it happens again. After it happened to me the first time I took to lubing the latch & cable mechanism as part of routine maintenance, w/every oil and filter change. Never has stuck since. Surely frustrating, but stick with it, best of luck.

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I got the hood open, did not see how I could access the latch or cable from underneath. I broke apart the grate on the grill and used a small pry tool that has a v shape in the tip to pull on the small exposed cable section and it opened.

Car would not start this time though, then I remembered a couple years ago when the car wouldn’t start, I was messing around with the fuel pump connectors and then it started (I had a thread on here about it, similar hissing sound but did not notice any smoke at that time). So this time I pounded on the fuel pump access door and it started right up. There was a slight amount of smoke that appeared to come from the lower side on the front of engine on driver’s side, where transmission is, but it disappeared to fast.

The oil level was fine. The coolant level was just above low. Did not notice any leaking from hoses.

I’m trying to figure out where that smoke came from, it had to escape from some place. Hopefully it’s just the fuel pump? I have noticed a fuel smell when starting the car in the past, it’s hard to pinpoint as I notice it from the front to back of car, I believe from even the exhaust pipe at one point. I always figured it was just because the car is a gas hog.

Such a thing may not be possible on your car. Good b/c it makes the engine compartment less theft & vandalism prone, bad b/c there’s no simple work-a-round when the latch sticks.

That could mean you need a new fuel pump.

You’ll have to keep monitoring the situation, eventually the smoking culprit will show itself. Smoke in the engine compartment is often oil from a valve cover leak dripping on the exhaust manifold or exhaust pipe. That would only happen when the engine is warm.

That may be normal. The engine computer injects a lot more gasoline into the engine than usual for cold starts. Some raw gasoline doesn’t get burned and comes out the tailpipe. If you notice a gasoline odor when the engine is warm, that’s definitely something that needs looking into.

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So looks like the seal between the water inlet housing and thermostat housing is what was smoking. I noticed some spots on the ground and seen dripping from where the thermostat and water inlet housing meet. I wiped the area with a towels and then seen some smoke from the water hitting the casing.

But still seems odd because the car was sitting for hours in negative degree weather when it first happened and can’t believe it got that hot, that fast to smoke?

No overheating issues. Temperature gauge is always just before halfway. Heater works.

I have a new thermostat coming. The thermostat has a gasket attached to it, maybe that blew out? From shop manual there is no gasket between the housing itself.

Now that hood is open, make a new video.

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You saw smoke from cold coolant? Is coolant leaking on to the exhaust pipe?

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Some thermostats use a gasket to prevent coolant from bypassing the thermostat. I must have replaced a dozen thermostats over the years among 4 or 5 vehicles. I don’t recall any of them not requiring a separate gasket between the thermostat housing and whatever it fits to. That gasket usually has to be purchased separately from the thermostat, b/c a single thermostat design can be used w/different types of thermostat housings.

Suggest to double-check the coolant level, both in the plastic overflow bottle and in the radiator. Good time to also check the coolant’s freeze protection level. You don’t want to risk overheating the engine parts. Safest to not rely only on the coolant temp gauge. I’m presuming what you are calling “smoke” is actually steam. The coolant probably takes some time (5 minutes or so at idle ) to reach steam temperature, but it doesn’t take that long for the exhaust components. So the early steam production might be coolant reaching something hot on the exhaust system. In any event, since you know you have a leak, common sense says to start by fixing that.

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I think another case where stalling and coolant leak are two separate coincidental issues taking us down that winding path.