Torchstang02

Hello I’m new here and was just wondering if any of you had any experience with this or could help me diagnose it. I have an 02 mustang gt that I recently realized had NPI, heads, and I bought a pair of used PI heads and swapped them on. Well after, the car makes this tapping noise that is pretty loud from the underside and relatively non existent from the engine bay, I can’t hear it at all after I bring it over 1250 rpms, and I can’t EVER hear it when I’m driving. It only makes this noise after it’s warm too. The car runs great and gets great gas mileage, so whatever it is doesn’t seem to be affecting performance, it just sounds real crappy to me. Could anyone help me figure this out? Thanks in advance.

houtex

Welcome to the forums!

Mechanic's stethoscope would be a good idea to me, so I could listen and pinpoint the noise better. It *sounds* like a little bit of bearing/rod knock, which may mean there's an oiling issue... but it being at idle speeds only... weird.

The things on the bottom side that could make noise, excluding the transmission items, are the crank, bearings, rods, caps, oil pump, chain sprocket, chains, crank sensor wheel, crank pulley... and that's it. Sure, the clutch maybe in some way if equipped, or the flywheel (which could have been cracked by the NEW POWAH, so yeah...)

Which is why I'd get it up in the air/on a lift and get that stethoscope, or a tube, or a screwdriver/rod, and get to listening for to find the area it's in, and then you'd know for sure.

The PI heads do increase compression, which would of course increase power, and then that could chain react things into... this. Still weird.

I hope that helps some. Do report back with any news/more questions!

Torchstang02

I actually went out before my class this morning and put the stethoscope on it, and I noticed I can very faintly hear it on the passenger side valve cover in the far back, but when I put it on the exhaust manifold on that side, I could hear it loud and clear. The noise seems to emit throughout the whole exhaust system, sometimes i think it’s loudest farther back, and some times I think it’s loudest under the engine, maybe a worn cam roller? Or a noisy valve?( don’t know if that’s possible without any issues with the way the car runs) I’m leaning towards valve noise because of how it’s loudest on the manifold and emits through the exhaust I just always thought with a noise like that from valve train there is something wrong and the car would run like crap.

houtex

Yup, sounds like the classic exhaust on that side's follower is shot. Maybe. Usually see that on the 5.4, but cylinder 7 or 8 has that issue, the roller bearings in the follower get messed up and it grinds out.

You'll need to pull the valve cover off and inspect it. Probably will be really easy to push it around.

It could be just the luck of the draw, or it could indicate an oiling problem. The other thing is that if it is worn, you can bet the cam is too, so you'll need to source a PI cam to replace that. And/or the PI head you got has a bad cradle for the cam back there and it's rattling. All *kinds* of things could be it at this point!

As far as it running like crap... the computer can adjust quite a bit, and so it may be masking things. Also, you may have caught it before it got BAD, so it's foolin' you.

And then... you sure it isn't an exhaust leak on one of those back ports, and when you rev past idle, things heat up and it's expanding the headers and closing the leak? Just a thought...

Hopin' some of that helps, continued good lucks thrown your way!

Torchstang02

I’m really hoping it’s an exhaust leak, and the last thing I want to do is roll around on the ground messing with the mid pipe or trying to reach the manifolds. I’ll probably take it to an exhaust place because I’ve become very tired of messing with the exhaust because it’s such a pain. Would it make sense that it doesn’t do it at all when it’s cold? That’s what’s throwing me off because I figured if it was something like a worn roller like it would do it all the time, even when cold, regardless, I’ll probably pull the valve cover this weekend and see if I can find anything out of the ordinary.

houtex

Well, the temperatures rising cause metals of different material and thickness and even shapes to do inconsistent expansion, so there'd be a place where things wouldn't quite be right, then they would. Whether it's the manifolds or the cam or the follower or whatever. Temperature makes a difference in everything. Even the oil has two 'states' of viscosity, which isn't right at all, it has a range. If it's mutiweight, that is. SAE30 wouldn't do that, but 10W-40 would, for example. Any/all those changes will drive ya crazy.

Good dang luck to ya, hope it's minor and easy!

Torchstang02

Thanks a lot! I appreciate the input and I’ll post an update if I figure out what it is, here’s a clip of the sound just because:

houtex

Def. sounds like an exhaust leak. Maybe from the collector. Just gonna have to get it up in the air and figure it out, but it doesn't sound catastrophic, just annoying.

/Again, from *waaay* over here, so...

SpectreH

I agree with Houtex....sounds like exhaust leak.

Torchstang02

That makes me feel better and I sure am hoping that’s what it is, I don’t need this engine to last much longer because I’ll be building one soon as it’s got over 200k and is definitely past it’s prime (as you can tell so is the paint) but thanks guys, I’ll post an update once I figure something out

houtex

Pfft. That's just gettin' broken in. Thing'll go 400K.

Torchstang02

I’d like to believe that, which I kind of do, but she’s a smoker already