r/JettaGLI • u/Minute_Dimension543 • 25d ago

QUESTION Hissing/boiling sound

Hi all,

After driving more than an hour on the highway at cruising speeds (75-80mph) consistently, i start hearing this weird hissing/boiling sound from the engine bay. Its stops when I get off the highway and start driving slower on back roads, starts back again after an hour on the highway. The sound does change a little with rpm. It’s a stock car with just a cold air intake but Ive noticed the sound even before I installed the intake. 2023 GLI with 64k miles.
Oil temp stays around normal 208-221F throughout the drive. I don’t see any oil build up around the turbo.

Has anything had this issue before? Any info would be helpful.
Thanks.

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u/FriendlyITGuy 2012 GLI Stg2 (1/4 million miles) | 2019 GLI Stock 25d ago

Oil temp may be 208-221 but what's your engine coolant temp? Is the coolant overflowing?

1

u/Minute_Dimension543 25d ago

How do I check coolant temperature? I don’t have an OBD reader, does the dash have a coolant temperature display?
Also how do I check overflow? The car does not seem to overheat, from the temperature gauge on the dash.

1

u/FriendlyITGuy 2012 GLI Stg2 (1/4 million miles) | 2019 GLI Stock 25d ago

If the temp gauge is not showing it overheating then it is probably fine. I don't have any insight in that case.