Bubbling noise at engine shutoff

[cogitate]

2018 titanium. For the past 10 or so days, I hear a bubbling or gurgling sound coming from under the hood when I shut off the engine.

I bought the car about 6 weeks ago and have already gone just over 4k miles, putting it at 59,960 today. When I bought it I felt a little blowback coming from the engine when I removed the oil fill cap. Today when I checked it, it felt like a stiff breeze.

The coolant was right at the seam on the reservoir, and looked as clean as can be. The oil also looked pretty clean. Nothing foamy on the oil fill cap. I haven't yet done anymore diagnostic work than that.

 

[Handy Andy]

Gurgling sounds usually mean a plugged or kinked hose.

Radiator and it's hose getting hot and can you hear the fan kick on when it is running to keep the engine at operating temperature?

Else something with the AC.

 

[tabijan]

When you shut off a hot engine, coolant temperature rises because it’s not circulating through the radiator even if the fans are blowing. The gurgling might be coolant moving from the engine to the reservoir. It might be normal but have the pressure cap checked that it’s holding 15psi or whatever spec is. Spec is probably printed or etched in the cap in psi or bar. If you think it’s safe to do so, pop and hood and look for movement in the reservoir corresponding to the gurgling. Don’t remove any caps until the engine is cold!

Sixto
2013 SE 1.6 hatchback 134K miles

 

[cogitate]

Gurgling sounds usually mean a plugged or kinked hose.

Radiator and it's hose getting hot and can you hear the fan kick on when it is running to keep the engine at operating temperature?

Else something with the AC.

Yes, I hear the cooling fans running. Engine temp is always good. It did idle a little rough yesterday, but nothing crazy

 

[Handy Andy]

Following @tabijan - suggestion - when you remove that coolant tanks cap - watch for those bubbles to rise up from that 3-way section of hose that is right by the thermostat and coolant outlet - there is another on the bottom side - but if the level in the clear tank drops quite a bit, it would explain the noise.

It also uses a "Burp line" that run across the top of the motor - from the rear side by the centerline where the rear bank of valves on the cover are - towards the front of the valve cover and over the injectors - running over across to the coolant tank - attaches thru a small port on the tank itself.

IF the coolant level is getting low - air and steam gets trapped in the back side of the rear section of the cylinder head where the exhaust valves reside - this is a very hot section as the hot exhaust doesn't have a place to go to shed it's heat when you're done driving - so if this seems to be the source of your noise, take a moment or two to let the engine idle to let the coolant flow back there and help take away some of that heat from back there- then just shut off the motor. It may help dissipate this noise - if letting it idle a few moments then the engine is shut off and it stops the gurgling - the issue is from the heat of that part of the cylinder head - not able to escape or get absorbed - it needs time to cool off

However, you own a Titanium - this may have a type of climate control system where the system "closes off" and moves the drum inside the climate control system once the system is not needed and you've shut off the ignition. It parks itself - you may be hearing the system park itself - this occurs after shutoff but not right at the shut off time - it takes several minutes to start and moves the vanes and drum for several moments - as it needs time to complete so you may be hearing the motors moving the drum and closing off the outside air port.



Depending on the system you have, Automatic - the one on the Left "Cycles" and can park itself to "Closed position" when you're parked and the ignition is off and it's not being used. The one on the Right is Manual and leaves itself where it's set at. But if you move the knob, with the ignition off it will cycle to "park itself" and the relocate to the new setting. But it may not be able to complete this until once the car is started again. Because; when the engine and ignition is off there is a timer on this length of time it can do this - so it will try to move to the new control setting - but it may not complete until the car is started again.

 

[Handy Andy]

Other things that may affect your noises are due to fuel - if you have a full tank some gurgling is possible due to hot weather and the vapor pressure of the fuel sloshing in the tank can make pockets of vapor and air pop or gurgle when the engine and fuel pump are shut off as a result of a stabilization of pressures - the fuel vapor "trap" line changes to an open position to trap vapors for re-burning on next startup - so this may change the fuel tanks pressures so the tank may have distended during driving - reforms to a given set shape and air and vapors move around to find stability inside the tank.

The "Breeze" you feel from the oil fill cap - may mean the your have either put too much oil in the crankcase, as overflow of the PCV valve port can not expel any crankcase fumes - so they vent thru the open hole you created when you removed what the oil cap once covered - or the PCV valve hose has kinked and or collapsed and its now blocking means to vent those very vapors you feel at the top of the oil fill cap port.

Replace - put back on - the oil cap and Locate the upper PCV breather (Foul air) hose to the valve cover and see if it routes to the air box - to a side port, and then remove the air filter cover and air filter itself and start the motor - does all that air now vent out thru that air-box vent? IF you're not seeing-or feeling any sort of venting action yet removing the oil cap you feel air moving out and smell a foul odor of exhaust and see oil spray that line may be plugged - fix it.

IF the line appears to be trying to blow out all that pressure by itself - then the PCV valve and it's hoses to the intake needs to be checked, re-seated and if broken - replaced.

If your Titanium is a turbo model - then you're 3-cylinder engine has a bad gasket and will need to be inspected and serviced - if the head gasket has failed.

IF that condition is not corrected, the engines own seals will fail and blow out - causing you to lose oil and pressure quickly and may leave you stranded on the road with dead seized motor

 

[cogitate]

Thanks for all the replies. I haven't heard the bubbling since the temps cooled off a bit.

I'll check the PCV valve and related components. It's not a 3-cylinder with turbo, but head gasket issues were my concern. Is all that blowback normal?

 

[tabijan]

I don’t think residual crankcase pressure is normal. As soon as you turn off the engine, the crankcase should be at atmospheric pressure. You might see vapors rising from the oil filler hole but not a rush of air.

You can get a kit at any auto parts store to test for exhaust gas in the cooling system which indicates a head gasket problem. I don’t know if it’s worth checking at this time.

Sixto
2013 SE 1.6 hatchback 135K miles

 

[Handy Andy]

I haven't heard the bubbling since the temps cooled off a bit.

Then your noises are related to temperature - not a maintenance problem - but of how the car handles itself in a hot environment.

It's not uncommon to hear fuel sloshing around in the fuel tank once parked after the engines' been shut off - so the other noises are also from having to use the climate controls or how the engine is dissipating heat.

It's the breeze part when you removed the oil cap that has me concerned - so to have extra pressure pushing out fumes the thumping and push of air is normal from displacement, but the system is designed to DRAW IN air when it's running to purge itself of those vapors they get captured and re-burned.

So if you place a paper plate or lightweight paper - over the hole, the air vacuum the PCV valve generates, should be able to build and hold the paper to the oil fill neck and provide some seal - that means the PCV valve is working - it's when the paper or cap is blown off trying to put it back on when it's idling - that is a concern.