rp0029

iTrader: (1)

Yesterday I had my exhaust welded up to my 68 Camaro LQ4 swap (with ls3 heads). Had the shop hook up my 2.5" flowmaster american thunder system to the 3" collectors on the dynamax headers and drove it back to my garage without O2 sensors plugged in. I also had them put in some magnaflow mufflers to quiet the thing down.

This has never occurred before, so I am assuming it comes from the exhaust, but when the car is fully heated up, and I mean, fully, the car makes a really high pitched whistle sound. It does not occur when RPM is raising, only lowering.

Listen to these videos. The first was me trying to video the exhaust, but at about 1:10, you can hear what I am talking about.
http://www.youtube.com/watch?v=qPg1R...eature=related

Here it is again from the engine.

http://www.youtube.com/watch?v=XDVoRqBsgJI

This is from the inside of the car. Watch the tach. When I hold it at 2,000, the whistle stays there.
http://www.youtube.com/watch?v=CoE5NcVOM2o

It takes about 15-20 minutes before it starts to do this. Notice it doesn't seem to be there when I am increasing RPM, only when decreasing or staying the same.

It most certainly seems much louder from the bottom of the car where the headers hook up to the exhaust pipes. I'm thinking it is the exhaust almost for sure. It didn't do this before. Any ideas on how to make this go away?

the_merv

iTrader: (88)

Change your Serpentine Belt.

99 WS-sick

iTrader: (2)

sounds like a pulley in the video's but you obviously would know to already check that. everything that requires "oil" of some type has it right? lol unhook the headers at the collectors and see wat it sounds like

rp0029

iTrader: (1)

I actually just put the serpentine belt in. The engine maybe has a total of 4 hours run time on it. Would the belt go bad that quickly?

And no I haven't checked the pulley. All this stuff is new. The only old part is the alternator and it seems to be coming from under the car. Although maybe I am mistaken.

I suppose the next step will be to run with open headers to see if the noise continues.... and if it does, to disconnect the belt.

the_merv

iTrader: (88)

Was it a new belt? Check the ribs..if they look shiny then there's your problem.

It could be a Pulley Bearing..check them when you pull the belt off.

rp0029

iTrader: (1)

It was a new belt. I will check it. If it was a belt/pulley, it would be there regardless of operating temperature, right? This whistle ONLY happens after 10-15 minutes of giving the engine time to warm. That is why I think it is exhaust, because it happens after something metal is heated to where it expands, like an O2 bung or something.

rp0029

iTrader: (1)

I'm thinking if I remove the O2 sensor, if it is the exhaust the noise will go away because the pressure will escape through the O2 sensor hole.

02ws.sik

How tight are your 02 in if they are not in tight ive heard a louder whistle then that.

rp0029

iTrader: (1)

I think that the O2 sensors are the problem. I just torqued them in with a 7/8" wrench. They are tight, but I am thinking not tight enough, or maybe somehow they are not sealing. I'm going to remove them and see if the noise comes back.

WeeWolf

iTrader: (16)

Think I saw where some guys had their PCV system plummed wrong and causing a whistle, its worth checking.

the_merv

iTrader: (88)

I've heard that noise with bad belts/pulleys.

Maybe a Ninja Turbo.

WeeWolf

iTrader: (16)

Try pulling the vacuum line off the valve cover and plug it and see if it goes away. If it was the belt I would think it would get worse off idle and it seems to go away.

check this out

http://www.youtube.com/watch?v=wj-gg...e_gdata_player

02ws.sik

Just dont fix it tell everyone its a turbo lol

gofastwclass

iTrader: (2)

I agree. I have an idler pulley bearing that is doing that exact same thing right now.

Pull the belt and run the engine for a short bit after it would normally do it, I bet the noise goes away. Crazy part is I bought a new tensioner from AZ and the pulley did the same thing after about four days but not as bad. Crappy cheap replacement parts. If you remove the pulley the bearing will feel a little rough or catch when you spin it in your hand.

the_merv

iTrader: (88)

I had an Alternator do it to me..had me lookin for a few minutes. The Belt doing it had me lookin for a few days..lol..

rp0029

iTrader: (1)

Well I'll look into it next weekend when I'm back working on the car. I have to store it about a half hour away in Miami traffic because I live in a condo, so I'll update you guys next weekend. My money is on exhaust, but maybe you all are right and it is the PCV/vacuum/belt.

sherman8r

iTrader: (6)

I had the same problem and I thought it was a belt until i got under the car and it was louder near the torque converter. ended up being my pcv was routed wrong and air was pushing out of my rear main. take off your oil cap while it's squealing and if it stops then its your pcv. fix it before your rear main gives up.

99 WS-sick

iTrader: (2)

bad a pillar gauge and everyone will think u pool hella early lol

Project GatTagO

iTrader: (7)

It has to do with the PCV system or it is a vacuum leak in the intake manifold. The noise only happens when the engine is pulling a lot of vacuum; when it is revving down; or when it is being held at 2000 RPM with no load. Those are high vacuum conditions.

Andrew

rp0029

iTrader: (1)

Andrew and Sherman8r - that makes total sense. I thought it was exhaust, but it doesn't seem to come from either side, only the bottom rear center, like it is the rear main seal. I have a breather on the rear driver's side valve covers, and the passenger side is hooked to manifold vacuum. My throttle body didn't have the vacuum port, hence the breather. There is no valve in the system. I suppose this is causing problems? What did you guys do?