Hissing at idle??????

[Prodigy926]

Alright... Someone might be able to help me with this issue. My car started making this really weird hissing sound comming from the engine after a long drive and you let off the gas. It happens after the engine goes back to idle and is a short air hiss. This is not anything ive ever heard before. It almost sounds like letting air out of a tire but then it stops after about 5 seconds. It isnt my airbox or anything. I was thinking that it might be a leak in the air flow piping. If someone else is having this problem and has gotten it looked at... please let me know asap so i can go into the dealer and not look stupid.

 

[Brian MP5T]

Alright... Someone might be able to help me with this issue. My car started making this really weird hissing sound comming from the engine after a long drive and you let off the gas. It happens after the engine goes back to idle and is a short air hiss. This is not anything ive ever heard before. It almost sounds like letting air out of a tire but then it stops after about 5 seconds. It isnt my airbox or anything. I was thinking that it might be a leak in the air flow piping. If someone else is having this problem and has gotten it looked at... please let me know asap so i can go into the dealer and not look stupid.

Have a look at your bypass line, where it meets the airbox. Also, check the vac/boost line to your wastegate, If this is leaking, you will notice a massive gain in power.

 

[Prodigy926]

really.... actually the car did seem a bit peppy tonight. is that a good thing or a bad thing>>>????

 

[Brian MP5T]

Yikes!!

really.... actually the car did seem a bit peppy tonight. is that a good thing or a bad thing>>>????

Very bad thing,

If that is where the leak is coming from that would mean that you are overboosing.

That line sends a boost to the wastegate diaphram. It opens a passage in the hot side of the turbo that allows exaust to bypass the turbine at max boost. It is what stops the turbo from going faster that the speed required to make your maxboost pressure. If this line is leaking it would require more pressure from the turbo to make the wastegate open and therefore your car would get more boost. If that boost goes much above ten psi you may start to detonate and **** your motor.

 

[Emode]

well i get this hissing too ive noticed, but my boost is steady on my guage

so i dont know

 

[Brian MP5T]

Hissing?

Is your hissing at idol or under load?

 

[Emode]

mine is at idle
and also after ive shut off the car

 

[Notorious]

If you have a boost gauge it could be that. Mine hisses a little bit under idle.

 

[Black Majik MSP]

If you have a boost gauge it could be that. Mine hisses a little bit under idle.

OK cool, I have a gauge & mine does too.

 

[MikeyK 5]

i have no gauges, but i have prodigy's problem exactly. stock boost. i brought it into the dealership, they heard it, inspected the turbo, and said it was a normal characteristic of the metal in the housing expanding due to heat. As the turbo cools, the noise goes away. So if it turns out to be something bad, at least now i have proof the dealer heard it!

 

[Brian MP5T]

MASS REPLY TO ABOVE POSTS

1.- If you hear a swoosh after you shut the car off. It's just the vacume that was in the intake manifold leaking back through the throttle body. NORMAL

2.- If you hear a hiss from your boost guage, use thread lock. NOT NORMAL

3. - If you hear a hissing and more power. It's probably a leak in the vacume/boost line to the wastegate. HOLY BAD

4.- If you hear a wicked turbo whine and your boost never leaves 0. One of your hoses has poped off. JUST FIX IT

If you have a question about a specfic problem. I'd be happy to help. Pm or on the boards.

Later...Brian

 

[Prodigy926]

Well check this out ..... my hissing almost sounds like a belt making a weird noise like a squeek but more of an air sound. It never did this before and all of the sudden it arrived in arizona. Never had the problem in ohio. Who knows anymore with this thing. the minute i think it is running great with 13000 miles on it lol something else questions me. Its almost like owning another Probe GT which i had 2 and had constant problems. Im used to this.

 

[Kooldino]

It COULD be something in the AC system.

 

[Prodigy926]

well i guess my car will once again go back to the dealer. i have a long list of things for them to fix.