I recently purchased an 03 Expy with the all aluminum 4.6. It has 40k w/no warranty.

When I start it there is no unusual sound what ever the outside temp is. After it runs for appx 5 min it will start something like a slight double knock. After it gets hot it will be louder.

The thing is it does not do it all the time. It will knock and then fade out and then come back in. It will not knock above 1500 rpm.

The sound is coming from the top of the engine, drivers side at #7 cyl, possibly #8. I used the garden hose and then the long screw driver method to narrow it down.

You can put the screw driver any place else on the engine and it is perfectly quite or just barely audible. If you put the screw driver on the last two valve cover bolts, bottom rear of the head, or #7 & 8 exhaust manifold, then you get an ear full. You can also hear it echo through the front left cat.

I checked all plugs today and they are all tight, so that is ruled out.

Any help would be appreciated, as both Ford dealers here have the usual response of "we never heard of the '03 4.6 knocking before". But they will be more than glad to listen to it for $80.00.

I will be more than glad to pay this if I have something to guide them toward instead of doing an expensive parts replacement program on it.

I posted this in FlatRateTech also. I need all the help I can get.

Thanks.

 

Does it knock louder when you're on the gas? Does it go away when you decellerate? Or does it just knock when you're cruising?

Did you check for sounds from the oil pan?

Could be a rocker-arm/follower that fell off, if the knock is constant and doesn't change in volume when you get on or let off the gas.

If it does change in volume when you're on/off the gas, that sounds like a wrist-pin or really bad piston slap.

 

It only starts knocking after running for appx. five minutes, and then only at idle up to appx. 1400 rpm. The knock will go away above this rpm whether under load or not. It is the same whether giving gas or letting off. It will not knock all the time. It will come and go, making it hard to track down.

I hear sounds from below, but not from the oil pan or block. Everything I heard was from the left head, and echoing down the exhaust pipe.

I warmed it up enough to get it to knock a few minutes ago. I unplugged each injector on the left bank one at a time to check for sound difference. There was no difference between a dead cyl. and a live one. This is leading me to look more toward the valve train.

 

Yup, sounds like it.

It can still be wrist-pin related, but it's starting to sound more and more like a rocker-arm/follower fell off (or is getting very loose) or a cam bearing (which requires changing the head).

Either way, sounds like it's time to get the valve cover off and have a look.

 

UPDATE:

I posted this at Flatratetech also. I need all the help I can get.

I finally got around to removing the LH valve cover. I made a plastic timing chain cover out of an antifreeze jug, then started it up and listened to everything on that head with a mechanics stethescope for at least 15 minutes.

No one lash adjuster or rocker had more noise than the other. I could still hear a very little knock when touching the head in different places. No noise at all at cam bearings. Each lash adjuster the same. Each rocker almost the same. Almost completely quite.

I stuck the probe down on the cast exhaust manifold and I could hear the knock again. If I stuck it to the flange where the downpipe connects to the manifold the knock was louder. Things are beginning to point toward the cat.

Has this happened where the cat had a knock? It's only at idle after running for 5-10 minutes, and only knocks randomly. Sometimes quite loud, at other times very quite, sometimes almost not at all.

 

If the insides came loose, it might "knock" ... that would actually be funny

Not to you, though ...

 

What's your oil pressure gauge saying? If main crank bearing came apart it will be low to no.

 

I only have the factory gauge. I was going to hook up a mechanical gauge until I saw where the sending unit is. I can not get my hand within 6 inches of it. I decided to wait a while on that. I think the oil pressure is ok because the low oil pressure message has only came up in the message center once or twice while the engine is turning over on the times it has to spin several seconds to crank.

One question on the oil pressure. Can someone tell me how much oil should be around the cam and lash adjusters when idling. The timing chain has plenty, but there wasn't as much slinging around the cam as I thought there should be. I lost almost a quart onto the ground even with the shield around the chain, so maybe there was more than I thought.

The knock is only on the drivers side around the exhaust manifold area. I can stethescope the block and intake with little or no noise. I can probe the valve cover bolts, exhaust maniford, and cat and pick up the knock. The bell housing does have some knock when probed, but it sounds like an echo. If it was in the torque converter or bell housing it seems that the sound would be on both sides.

I drove it this evening, and when I got to where I was going I opened the door and listened before getting out, and there was the knock fairly loud. I came home about 30 minutes later, opened the door at the house, listened, no knock. This is driving me nuts. I have had people ask me why my engine was knocking, then it will stop for no reason.

 

i had a knock very similar to that on my 99 f250 with a v-10, drove me nuts, ended up being the flywheel was cracked. i have pictures posted of the flywheel. my knock didnt do this all the time, and i couldnt hear it around the bellhousing. the sound would change pitch when you put it into gear and took it out of gear. it would knock at idle and when you reached speed, but not while accelerating. drove me nuts. finally pulled trans and found a 6 inch crack in the flywheel.

 

I looked at your pictures. Did the knock come and go, and was it isolated to one side like mine?

 

funny thing was that i couldnt hear it with the stethascope, or the screwdriver trick, but it was loudest tward the back of the engine and on the lift i could hear it really good, but couldnt determine if it was coming from the engine or trans. the only way to see the crack was to remove the trans.

 

my knock would come and go for a while then it got worse and did it all the time. took about 3 or 4 weeks

 

For the last 2 mos. I have read on this topic until my eyes would bleed.
I had the issue with a clacking/rattling/ticking/rattle sound in the engine compartment on a 2000 E150 5.4L Triton (205,000 mi.) Basically, what was actually spark knock on acceleration. It also likely lead to our poor LTFT and STFT readings.
I could rev engine in park/neutral as high as I wanted and would NEVER get the noise. That fact, and, that no codes were being thrown made this next to impossible to find the origin/reason. We tried all kinds of repairs/fuel treatments/octane increase/MAF sensor cleaning, heat shields, cats, etc..., based on whatever I found from endless forum searches. Nothing worked. But, now finally it is fixed. The DPFE ports were caked/occluded with carbon and when we just touched the hoses, they also just crumbled. The problem existed for almost 3 yrs. It's now FIXED.

Also, Ford had bad DPFE's early on and this was a big deal for performance issues. I did not actually need to replace it however as it just needed cleaning, and I suspect it is/was not the original anyway.