Indy-Vert

So, Old Bessie is starting to get cranky in the morning after not being driven for a day or two. Upon start-up, I get a knocking noise that speeds up when throttle is applied. The noise disappears after several seconds and never occurs during driving...only at start-up. The noise reminds me of the sound of crank-slapping as a result of a spun bearing or detonation. The noise doesn't occur at every start-up but it's occurred 3X in the past month (about 60 start-ups).

Oil pressure is, and always has been within spec, as well as coolant temp. No leaks, no evidence of anything else being out of order. No prior issues except for replacing the stock composite intake manifold with the aluminum/composite Ford Racing manifold and water pump.

A little research into the bearing design makes me beg the question of how one of these bearings can spin in the saddles.

Also, what type of noise can a faulty timing chain tensioner produce at start-up?

Bessie's a 99 GT 4.6 SOHC stock with no mods, 119k with oil and filter changes done religiously every 3k miles. Automatic.

Any input is great...am currently panicking thinking the worst=expensive bottom end rebuild.

petrock

Sounds like one or more collapsed lifters. One or more is probably leaking out the oil inside of it while the car sits and it takes a couple seconds for the oil pressure to build up when you start the car in order to fill them back up again. The knock you hear is the push-rods bouncing between the lifter cup and the rocker arm. If you know how to remove/install a lower intake manifold then its only a little bit more work to replace the lifters.

96t-bird

Do not know what is causing the knocking sound. But Mod motors do not have the traditional push rods and lifters. Maybe another member can help out with more info.

Stevo86

No just no and no. A 1999 GT does not have any of the parts you just mentioned.

It's possible you have a collapsed follower which is underneath the valve cover but that is usually a pretty constant tapping not a knocking.

Mod motors are notorious for knocking after an oil change while they are building oil pressure. I would see about putting a mechanical pressure gauge on it to see if it starts out with oil pressure right away or not. If it doesn't my guess is something in the oil pump.

WJL

search 4.6 ticking noise, you will find a lot of good information

petrock

Your right that it doesn’t have push-rods. My mistake. But it definitely has hydraulic lifters and roller rockers. The lifters are opposite the valves and the roller rockers bridge across the top of the valve stem to the top of the lifter and the cam runs on top of the rocker in a SOHC motor. Lifters are sometimes called lash-adjusters or tappets, btw. And roller rockers are sometimes called followers. Here is a link to where you can pick up a new set from latemodelrestoration.com:

http://www.latemodelrestoration.com/...-Adjusters-Set

Or you can contact your local ford dealer and ask for part # 6C501 (lifter) and 6564 (roller rocker). Or check out this link to motorcraft.com's parts page for the heads which includes an exploded view of the heads & cam assemblies showing both the lifter & rocker arms:

http://www.fordparts.com/Commerce/Ca...o=6c501#Search

Although I’d pick them up from rockauto.com for $6-9 a piece (depending on brand) vs the $10 a piece from latemodelrestoration.com or $17 from ford. Just sayin’…

My theory that the ticking is one or more collapsed lifters still stands. The ticking in this case would be the top of the lifter bouncing against the roller rocker as the cam spins.

uberstang1

When u say it is withing oil pressure spec how did u test that, are you just going by the stock gauge?

Indy-Vert

Stock gauge. I suppose fitting up another gauge that will quantify the pressure instantaneously throughout the start-up and warm-up process would be highly helpful, so I'll do that and report with my data. Do we think I'd be able to successfully pinpoint the source of the "knocking" with a modified stethoscope?

Update: starting to notice some mild-to-moderate "rough throttling" when it starts now. The motor sounds rough(although faintly), the car shakes mildly when revving and I am noticing some sluggish throttle response when revving in Park, all at start-up. Haven't driven it since these new symptoms appeared, only started and revved. The knocking is gone while the roughness is experienced, as it appears for a few seconds at startup.

Derf00

What weight (viscosity) oil you using? It could simply be the oil is thicker than what you used before so it takes a couple of seconds to get going or the old oil was so worn it was water at startup.

Don't rely on stock gauges to troubleshoot your engine. They are smart-idiot lights.

needmorespeed

I have had some issues with a rough idle on startup. The revs build and drop. This never happends with enough regularity to cause me any concern and is only a few hundred rpm difference. The motor runs fine at all other times, except the lifter tick but that is another story. Also, you shouldn't be revving your motor at startup. I don't know what time frame you are talking about but if you jump in, fire it up and rev it up to 5 grand, that isn't good for your motor. You gotta let everything get up to temp before you start revving it.

As an aside, 3K oil changes are probably wasting your money, owners manual calls for changes at 5k.