water sound

[mks64]

i have a 97 out back sometimes i can hear a water suction sound coming from the dash area,any idea what it might be?

[Jay!]

That's engine coolant moving through your heater core. It's normal. If it sounds really slosh-y, you may just have air in your system...

[mks64]

ok thanks mate

[4Wheel]

Just drain all the coolant and it will go away. Joking of course.
Might try replacing the radiator cap and make sure the seal area in the fill hole is smooth and clean.
then keep your overflow reservoir at it's proper levels so it will self burp the air out over time.
as he said some noise will always be present, it's a question of how much air is in the system.
Does your heater make hot ALL the time or just when you rev the motor?
This would be indicative of low coolant.