uptown193

I have this annoying hissing sound coming from my engine. It sounds like it is coming from the exhaust manifold. The mechanic changed the passenger side front exhaust manifold gasket for free and still hissing. Anyone know what is causing this hissing. It happens during idle and more when I drive. Thanks.

Y-ME

Sounds like a vacuum leak, when the manifold donut or gasket is leaking it has a feathery sound due to the pulses of the exhaust coming out, it would not be a steady hiss. A vacuum leak will emit a steady hiss, look for disconnected/cracked hoses If nothing spray some carb cleaner at the base of the manifold, if the hissing stops for a bit you need a new intake gasket.

uptown193

Well actually it is a somewhat fast on and off hiss when idling but when I press the gas the hisses is faster. Does that change anything or explain it better?

jimmers

Sounds like a vacuum leak to me.

Y-ME

Yup higher revs mean more vacuum pressure.

surfer92

Use a hose of some type, to help you localize the leak or spray soapy water around hoses and connections while car is idling.

WW7

Maybe there's a snake hiding in your engine and every time you start the motor is phissses him off..Ok maybe not........Probably a vacuam leak, or one of the small tubes at the top of the exhaust manifold has a crack in the weld, I have seen this happen before....WW

uptown193

yea sounds like a good idea. It is definitely coming from the area of the front exhaust manifold that why he changed the gasket there but it didn't work. I am not to mechanically inclined and don't really have time to do it. But I am willing to try if I can save money.

uptown193

Hehehe, I wish that was the problem it would be resolved fast and I would have a pet in the end.

I might be better off bringing it in to my mechanic. I will see if I can record the sound and post it. I do not have a private garage and the weather out is bad and I work all day.

Vette73

uptown193

Lmaoooo

RUU

Yeah, some ricer trying to save money on a serpentine belt. Wonder if he's related to the guy that put NOS energy drink (2 bottles, no less) in his sport bike's gas tank.

uptown193

FYI,

I just got my car diagnosed for a hissing sound from engine bay and I was just told it was due to a bad spark plug or wrong spark plugs.

chuckvin8

You need to check the air injection tube/manifold. it has a reed valve on top that is a one way valve to let air into the exhaust manifold. you can find this with a stethoscope with just the empty hose to the ear peace. or use a lite cigarette slowly passing it around the manifold with the engine running.

uptown193

I am copying this post from Chuck at COW from my other thread I made. He works on my car but was not the one who put the spark plugs in improperly, someone else did that.

Here's the deal.....


You have an aluminum headed C4 engine. They use LONG REACH GASKETED plugs.

The dick you took your car to the last time for it's spark plugs cross threaded the #2 spark plug hole trying to put a SHORT REACH, NON GASKETED (taper seat) PLUG into a car that dosen't use one.

You're lucky the head didn't have to come off.

For anyone that has worked on a C4 with the stock exhaust manifolds and air pump check valve and plumbing on the passenger side between (angled) plugs #2 and #4 KNOWS FULL WELL that it takes divine intervention to get that spark plug threaded correctly and snugged down with all that emissions crap in the way.

Be thankful that he didn't do any more damage than he did.

It seems to be running much better from what I see, but I'll take it for a ride tomorrow and evaluate it more.

I haven't seen this car for a year or so, I wanna look it over carefully.

BTW...That new paint job sure does look nice!
Chuck CoW