today i started up my 99 f150 xcab 5.4l everything was fine. drove about 3 miles and notices a knocking noise. pulled over and it stopped. reved the motor to 2krpm and it started knocking. i took some footage wondering if anyone could help me out with this... greatly appreciated

http://www.youtube.com/watch?v=0FnKH...TGXH60&index=3

2k rpm

http://www.youtube.com/watch?v=3mLop...TGXH60&index=2

idel

http://www.youtube.com/watch?v=yl8Kj...TGXH60&index=1

revving

 

Exhaust leak. probably one or more of the exhaust manifold bolts have broken or maybe the manifold itself has cracked.

 

sound seems to be coming from bottom end or under manifold.

 

Helpp

 

it sounds worse than a exaust leak but i guess it could be. hows the oil level and oil pressure ? what kinda oil and filter you running on it ? how many miles?

 

oil is fine level and pres. 153k on the clock. running synthetic 10-40 and k&n

 

its an exhaust leak period.

 

from manifold?

 

yep.
Ok I'm only 90 percent certain thats what it is. Its very common for these trucks to make that noise when the bolts break or the manifold has cracked the sounds location can play games with you. Check and see if ALL of the bolts are still there inspect the manifold for leaks.

 

How many miles are on it? What oil? Second video sounds like a rod bearing. Others sound like an exhaust leak. Ive had manifold leaks on both my trucks. When they leaked, you couldnt tell the studs were broken and there were no signs of a leak. They can sound like a slapping sound as the gasket is flapping around, but... it's normally more metallic sounding and not so pronounced. Ive also had bearing failure and timing chain guides that went bad. Mechanics stethoscope will help pin point where it is.

 

just took a look. and the 4th cylinder both studs are broken. i checked all the studs aswell and just 4th top and bottom are bad. but will that still make that loud of a sound?

 

Passenger side is more common for some reason. Probably due to the design of the Y pipe. Get the leak fixed before it gets worse and hopefully that is it. Since it "just happened" That's most likely it. As bearing failure normally doesnt just happen all the sudden.

 

whats the probability that that's the culprit. and how much should it cost to fix. and should i buy new manifolds

 

Call around. Not an easy job.. I think ou can expect a bill 600+. Stock manifolds arent that much but if it were me I'd seriously consider long tube headers.

 

well money is short.. would this be also caused by running straight pipes with cats