I have read many threads on this after doing a search. I don't know if I have the same problem or not. There are no engine codes being thrown, already checked that. Can't find a vacuum leak anywhere; it sounds a little like one. When the engine is cold, the noise is not there. Definitely coming from the driver’s side. I looked for broken bolts, but can't find any. The sound is also definitely coming from inside the engine compartment. All of the exhaust pipes are tight off the manifolds and back to the cats.

To those of you that have had this problem, do my symptoms sound the same?

Truck:

1999 Ford F150
5.4
Auto
4x4
90,000 miles

Thanks!

 

My broken bolt was the last bolt on the pass. side ex. manifold.

 

if you have not looked, look for black carbon built up along the exhaust system, guaenteed where you see that is where the leak is at. also look for it around the exhaust manifolds,

Lance

 

Ok, I spent a couple hours with it tonight. I don't see any carbon buildup. I pulled the throttle body cover off, left the engine on and had someone put it in drive with the foot on the pedal. If I put it in neutral or park the noise isn't as noticeable. It seems like the noise is more centered on the top of the engine. I saw some vacuum canister on top. Anyone know what that is?

 

If it is coming from the center of the engine, hopefully it is not a spark plug about to blow.....have had a few of those pop out. They usually will sound a little like an exhaust leak at first due to compression leaking by.

 

if you don't have a stethiscope to narrow down the noise take a long hose about 1/2 inch dia and put it to your ear while moving it around the top of the engine it will help alot to find the niose. The biuld up I was talking about was actually removeing thr TB and there are several inlets in hte intake the one that is usually clogged the worst is the egr valve. which can cause problems.

Lance

 

I picked up a stethiscope today and spent a couple of hours. Still could not pinpoint it. So, I took it to a local shop. They had a 98 in there with the same noise. On that one it was the EGR tubing that runs from the exhaust manifold to the EGR valve. That valve on the top of the engine I was talking about is the EGR valve, BTW. The mechanic said he'd be able to pinpoint it for $60, but said he'd start with changing the EGR tube. The tube is listed for about $40 from Ford. I think that's where I'll start for now.

BTW, I did check all of the spark plugs, and all of them were nice and snug.

 

when you do change the tube let us know what you see wrong with it. wonder if it is clogged or what. If it is clogged you may be able to clear it up with out buying a new one.

 

Sorry it has taken so long to get back with this....

I removed the EGR valve and tube. I could not find any obvious cracks, holes, blockages, ect. Someone told me that it could be an exhaust gasket or manifold because of my loss of fuel economy as well as the noise being more noticeable at normal operating temp. I usually average around 15 mpg and it has dropped to about 9-10 mpg. So, I used that excuse and bought some shorty headers that arrived today. I will be doing the install on Saturday. Any tips or tricks before I start? Anyway, I'll post up if the swap changes anything with my original problem. Thanks for the posts!

 

After several hours of wrestling with the overall job, and a little cussing, the headers are installed!!! The noise I had before is gone. I'm guessing it was from a broken pipe flange bolt on the driver side and a broken manifold bolt on the passenger side. I did find what appeared to be a minor crack on the manifold flange too. If anyone needs specific details or tips, let me know. There were a lot of hangups that required some thinking to resolve. Here's some pics...

Driver side manifold after removing inner wheel well..
[IMG]photos/data/500/ds_exh_manifold.JPG[/IMG]

Same as above, passenger side
photos/data/500/ps_exh_manifold.JPG

Broken stud
photos/data/500/broken_exh_manifold_stud.JPG

Header installed
photos/data/500/header_installed_ps.JPG