Ok, I'm almost 100 percent sure this noise is being caused by an exhaust leak. I've done the screwdriver trick and the hose trick to tell whether or not its a stuck lifter or exhaust leak. Tapping noise still subsides when the enging is idling or at crusing speed. I think I've narrowed it down to a small area but its really hard to get to and I can't really see it. My question is how much would a fix for this approximately cost if I took this to a mechanic. I'm fairly sure he'd have to take the manifold apart to get to fix the leak. I was just gonna JB weld the sucker if I found it but I can't really get to it. Any advice/opinions?

 

Could be you lifters bleeding out. I had a helluva time with oil pumps in my TownCar. My lifters had to be replaced b/c the seals dried out due to the lack of oil. Have you had any oiling problems?

Is it a cracked exhaust manifold? I've heard those crack perodically.

Maybe you smog check valve across the back of the heads is leaking like mine...?

 

here's a couple of things to check: there is a small bracket with a pointer on it used for your timing, above your harmonic damper. check to make sure it hasnt been bent down and is rubbing against your harmonic damper. another thing you can do is take the belt(s) off and run the engine to make sure the noise isnt coming from an accessary, you can maybe get in a little closer with your ears to see where the noise is. a stethoscope isnt that much money and works a lot better than a screwdriver. also if the clicking gets better after it warms up its prob just a hydraulic lifter that hasnt pumped up with oil yet cause its cold, or it could mean your engine is getting a little old and loose lol. good luck!

 

The noise is barely audible when the truck is idling. I can hear it on startup and when the engine is stressed like when I'm accelerating after I reach cruising speed it gets quieter. I used a hose stuck up to my ear and poked around. I have narrowed it down to like a 2 inch square area but can't get my hands or tools to work on it. Maybe its the smog sensor but I don't know where that is. The tapping seems to be coming from in right where the manifold connects with the pipes. In between the last two (closest to the fire wall) to be exact. By the way its an inline 6... Well I'm fairly sure thats where it is coming from cause thats where the sound is most audible thru the hose. I don't hear it thru the hose until I get one end right up next to where the first of the 6 pipes connects in. By the way I wish this was as easy as my '77 jeep cj5 to work on!!! I'll check tomorrow with a stethascope. I've got one or two laying around somewhere.

 

i would really advise against using any kind of glues or sealants for sealing up exhausts. first of all they prob wont withstand the heat and second they will crack off eventually. not to mention you will prob just make a mess for when you do want to repair it correctly. it may be that if it is an exhaust leak all you need to do it tighten up the exhaust manifold bolts a little. or worst case, the gasket between the exhaust manifold and the engine is coming apart and it just needs to be replaced. i cant believe that an in line six exhaust minifold is that hard to get to? what vehicle is this in?

 

'96 F150

 

 

>The noise is barely audible when the truck is idling. I can
>hear it on startup and when the engine is stressed like when
>I'm accelerating after I reach cruising speed it gets
>quieter.

You absolutely have an exhaust leak. When the engine is not under load (idle and cruising) the exhaust pressure is low, so your leak isnt as big. If you are under load (accelerating), the exhaust pressures are bigger and your leak will increase and so will the noise.

Any valvetrain noises are completely independend from the load on the engine and just change frequency with rpm.

Now I haven't seen a straight 6 in a 96 truck but if you cant even feel the leak with your hand or even get there, just bite the bullet and have it fixed. I doubt there is any cracks, maybe just the gasket gone bad. you should expect in the range of several hundered $ to have it fixed, in case there is no problem with cracks. Maybe $200-$300 tops. The manifold will have to come off. All surfaces will need to be cleaned, new gasket / sealer and put back together.

Do not attempt to put JB weld on it. YOu will only make a mess. JB weld isn't made for those temperatures.

Also, fix it sooner than later. It will get worse and even if you only have a defective gasket now, the leak can eat into your metal, damaging the head and / or the manifold.

Hope this helps.

George

 

Thanks for confirming my suspicions. Thanks to everyone for their advice and info. Mechanic.... HERE I COME!!!!!