water boiling/bubbling sound coming from behind the dash after engine is shut off ???

[bobcat]

I have a '99 W202 with air conditioning. I've been hearing a strange water boiling/bubbling sound coming from behind the dash after engine is shut off. I can hear it, even if the vehicle is parked on an busy street with the engined turned off. It continues for 20 to 30 seconds and then goes away slowly.

Is there something wrong with the engine's coolant system, the climate control system, or both? The coolant was completely flushed before the summer, but the noise just started in the last few weeks.

Thank you for any advice!

 

[william silver]

I don't want to alarm you in any way but I had this noise (twice) when I had an Alfa Romeo GTV coupe. Both times the head gasket had gone and the noise was the water getting where it shouldn't. I hope it isn't the same thing for you.

 

[Brian WH]

I have a '99 W202 with air conditioning. I've been hearing a strange water boiling/bubbling sound coming from behind the dash after engine is shut off. I can hear it, even if the vehicle is parked on an busy street with the engined turned off. It continues for 20 to 30 seconds and then goes away slowly.

Is there something wrong with the engine's coolant system, the climate control system, or both? The coolant was completely flushed before the summer, but the noise just started in the last few weeks.

Thank you for any advice!

As it started in the last few weeks, I assume you have just started to use the "Heater" for the first time since you flushed it out????????

If so it is air in the heater element under the dash. Cure is to check water level, if OK, run engine with heater on full for a while, a 20 min run is good. When you get back, turn off engine and check water level again, top up as necessary. Listen for bubbling which hopefully will have gone.