Good morning Rennlist,

I have noticed a sound of rushing water when I start my car up. It comes from the passenger side in front of the dash. It also occurs when I begin to accelerate from a stop...
My mechanic said it may be air in the coolant, but I don't know so I want to pose the question to you.

Thanks for the feedback!

 

It is air in the coolant. In particular, its your heater core. Its located in the middle of the dash, behind the center console.
Its a pain to get to but unless you see coolant on the passenger side flr, I wouldn't worry about any leaks. You should bleed the system and the sound should go away.
Regards.
Raj

 

I had this problem in my 951 and kept bleeding the coolant over and over again, but it would never cure the rushing water sound that you describe. One day I was messing around with my battery and realized whenever it was tilted from one side to the other you could hear the fluids inside rushing around which explained why I heard the sound right in front of the dash.

 

Very good news, thanks Raj!

Next question, as a noob, how do I bleed the coolant system???

 

Turn the car on, let it get to operating temps. Turn the temp control to full heat and fan to full and open the bleeder bolt on top of the coolant neck pipe on the head.
Sometimes, it might take a couple of tries to get all the air out.
Its a 12mm bolt, one of the only few in the car.
If you can't locate the bleeder bolt, I can post some pictures later.
Raj