Help with other car

[stargazer_61]

Okay, I know that this is the BMW forum, and you all have been really helpful to me, so I am giving this a go as well...

My wife's '96 Mustang 4.6L started making a loud, metallic tapping noise suddenly. Increases and decreases with engine RPM. I cannot isolate where it is coming from, but it seems louder at the front and underneath. I have listened all over the place with a red-neck stethoscope (oil pan, valve covers, engine valley, next to crankshaft pulley), but cannot hear anything unusual going on inside. Looked everywhere for something loose, but cannot see anything. I even pulled the drive belt to see if an accessory was causing it, but it was still there.

If any of the mechanical geniuses here have a clue or have seen anything like this, I would sure appreciate some help here.

Many thanks,

John

[Kalevera]

Is it a knock or a tap? Any computer diagnostic info -- check engine/service engine soon lights/codes?

best, whit

[stargazer_61]

It is a tap, not a knock. The CEL is on, but I do not have an OBDII code reader to get the code. It was on before the tapping started, came on a couple of weeks ago, after I put in a new radiator.

[Five35]

if it's making the noise while the car isnt moving, it's likely piston slap or something to that nature.. Whatever it is, it doesnt sound too good

If it is detonation, you might have gotten bad gas or you might want to start trying 93 and see if that helps.. I highly doubt it's detonation though as that is more of a marbles in a tin can kind of sound.

[632 Regal]

sticky lifter? Does it have an oil pressure guage? anything else out of the ordinary? What was it doing when the noise started?

[stargazer_61]

I don't think it is a sticky lifter. I've listened to the valve covers with a hose and the noise doesn't seem to be coming from there. Oil pressure looks good from the instrument panel.

[joshua43214]

bet either the timing chain is loose or one of the guides broke. Ford is totaly clueless about OHC V8 engines, that 4.6 was a piece of junk compared to the 5.0. I used to hear bitter complaints (as well as scary noises) coming from the american car guy in a shop I worked in, and he thought I was for working on Eurocars.

Crank associated noises are usualy deeper knocking sounds from the bottom, cam associated noises are usualy taping sounds fromthe top, chain associated noises are usualy taping or scraping and can't be located.

Take the pony to the glue factory and get her something cool, like maybe that 1 of a kind electric basket case that someone posted. Its in Las Vegas so it gives you a chance to go party with a good excuse.

[stargazer_61]

Joshua, like you I am a happy 540i driver. As much as I would like to put this Pony out to pasture and not to stud, that is not really a practical option. However, you have given me some valuable information on where to continue looking for the source of the noise. Thanks.

[NovceGuru]

if it's making the noise while the car isnt moving, it's likely piston slap

Our Jeep I6 has had piston slap for about 50k now :P

[stargazer_61]

Well, after a whole days work, I nearly have the timing chain cover off, to look and see if one of the guides broke, per Joshua's suggestion. It is not a trivial task, to say the least. Pull vibration damper and all accessories except the A/C, valve covers, drain oil, drop the frame reinforcement bracing, pull the engine compartment brace. Am in the process of dropping the oil pan, that should be the last piece before the cover comes off.

On the plus side, there is no oil starvation in the valve train, and it is extremely clean, not like those sludgy pictures Bill R posted a while back. The right bank has a bit of varnish buildup, where the left does not. Cam lobe wear looks to be normal, with only marks from the rollers. If it isn't something in the timing chain area, then it is looking like either a broken piston pin, causing slap, or a sticking valve, as has been suggested. If it is the piston, I will be in the market for a low mileage 4.6L SOHC within a days roundtrip drive.