Funny sound when it starts--1999 corolla

it’s happened 3 times now from cold starts…as soon as the engine is turned on it sounds maybe like water rushing or some kind of hissing sound while the engine is simultaneously idling really high. it lasts for about 10 seconds and then goes back to normal. it’s hard to decipher the noise. it’s at 76,000 miles and had it’s 75,000 mile check with no problems. help, please.

Have the cooling system pressure checked. This sounds like air (maybe, air from the cylinders) in the coolant.

A vacuum leak would cause a hissing sound and a fast idle. Check the condition of the vacuum hoses on the engine.

ok, thank you. appreciate it…

will look at that too. thanks.

oh, i meant to ask…does it have to be making the sound at the time of being checked by a mechanic or is a vacuum leak something that can be found on it’s own. i ask because it’s not making the sound consistently–yet…

It would be better if the problem occurred in front of your mechanic. However, he could do a visual check of the hoses anytime.

It just occurred to me that a leaky brake vacuum booster could also cause your problem. Next time you get the hissing, see if tapping the brakes has any effect.

ok, great. thanks again–i’m so grateful for the advice!