hi there,

yesterday i after i had turned off the engine i was fiddling around the front of the car when i heard an unusual sound. it was air escaping but in little bursts. it sounded exactly like someone dripping cold water onto a hot stove one drip at a time. just like a tap dripping itself dry the noises were fast to begin with but slowed down and then stopped althogether.
i turned on the engine and tried to repeat the sound to get an idea of where it came from but those clever little gremlins were ready for me and didn't perform.

has anyone any idea what this might be?

thanking you in advance as always for your help.

jb

My first guess would be coolant from the expansion tank.

Any cooling issues to note lately? High temps? Any liquid on the ground after you park?

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

thanks for the speedy reply, i will investigate further as soon as i have a mo this weekend.

certainly haven't noticed the dials showing any overheating. i thought it might be something to do with the self-levelling suspension, i am not even sure i have self-levelling suspension but have seen it mentioned many times so presume i have.

thanks

jb

Hey jab.
I think you are describing two different noises, both of which are normal (if they turn out to be what I am about to suggest they are). Let me start by asking: Did you have your air conditioner running before you turned off the car? (I am refering to the one time the noise(s) did show up).

Well, if you did have the A/C on here is my reply:
When you say that it sounds like "air escaping in short bursts and diminishing as time elapses", this sounds to me like the freon running back into the low-pressure side of your A/C system. It sounds something like (Psssssss.... Ppssss..... Pppsss... Ppppss).
This noise / sound usually last a minute, no more than two minutes after the car is turned off. It is perfectly normal for the car to make this noise.

The second noise you described went something like "water falling on top of a hot stove". Well.... Once again, if you had your air conditioner running before turning the car off, it is normal for water to slowly leak out of the pan that is situated under the A/C evaporator. The evaporator, in simple terms, is a small radiator underneath your dashboard. The A/C coolant runs through its inside and air is cooled when it comes in contact with its fin. This produces "condensation". This condensation (water) is dumped outside the cabin after being collected by a drain pan underneath the evaporator. It is possible that the slow drip of water from this pan is falling onto the muffler or some other HOT surface underneath your car.

This is more than you asked for, buit I hope it helps.
yamil:p

thank you for your help,

just one small thing.....i don't have air conditioning!

please accept my apologies, my description wasn't very clear, i am only describing one sound, i just offered two descriptions of the same noise to try to give a better idea of what it sounded like.

justin

If you don't have airconditioning, my whole theory gets shot down.
Let me ask something else:
Has it continued to happen since that one time?
Does it happen every time you turn your car off?
Do you remember running over a puddle that day right before parking the car (was it raining)? This last question might seem silly, but if you run over a puddle you will get the undercarriage wet and the water will begin to drip onto hot components (ie. muffler, catalytic converter, etc.)

When you do find out what it is, let us know. I am kind of intrigued!!
Sorry I couldn't be of more help.

thanks once again, sorry to shoot down your theory so rapidly, i have been using the bike this week so haven't had a chance to test the car, but i like the water theory, because i was testing the screenwashers a little earlier, so it's possible some water was dripping.
i'll let you know.