Mustang Bullitt Forum banner

Some cold engine KNOCK feedback from FORD...

1716 Views 24 Replies 18 Participants Last post by  Bullitt 289
Here's what the Ford engineer told me today:
"The 4.6L's have switched the piston to a smaller, lighter, higher performance shorter skirt piston that is designed to perfectly fit a warm engine. There may be noise when the engine is cold for the first few minutes. This is normal, hence, there is no fix for cold engine knock planned or in place. The noise you hear causes absolutely no wear and tear."
Here's what I said...
"Yeah, but the noise I get is the engine is coming apart, I can't believe there's no wear, and is there from 2,700-4,000 until the temp guage is mid. arc, which usually takes at least 15 minutes of warm-up.
90% of my driving is 20 minutes hops at the beginning and end of 12 hour shifts, so 90% of the time I'm either short-shifting or letting the car warm up 15 minutes for a 20 minute drive."
His reply...
"It could be that your car has the noise louder than most. We'll have to meet when your engine's warm so I can hear it in person."
Seems we keep going around in circles. I had left my car overnight at Ford in October so the mechanic and foreman-supervisor could hear the knock. Now we're back to this again. I'll keep you all posted.
21 - 25 of 25 Posts
<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2002-01-10 06:22, Bushmaster wrote:
did your engine builder say that this is something to be concerned about (the short skirt piston characteristic) or is it an area that needs to be corrected by Ford? </BLOCKQUOTE></FONT></TD></TR><TR><TD><HR></TD></TR></TABLE>

I talked to a local race engine builder and he said its nothing.
I'm joining in here also....mine does it too. It's right when I start #4841 up and leave the house...on acceleration. Also, as Dennis said, mine is really, really loud and it sounds like my engine is falling apart!! It does go away, but only when #4841 is warmed up....about 5 minutes or 5 miles down the road.

I guess I'll just keep reading the posts, see if a solution is finally found on this one....
oil analysis is a good way to see if your getting higher levels of wear. one thing it own't do is tell you exactly what is going bad but does give you an idea of what may be happing. to learn exactly what oil analysis is and does i had set up a page that will give you a better idea of what,why, and how it works. at the bottom of the page is another oil analysis lab that not only gets you the report but also they give you a personal consoltation which is very helpful because there's more to understanding these reports than just a high or low reading. don't get me wrong, it's not you wont understand it and it's complex but all the tests have wear numbers,visc numbers,nitration,oxidation and so forth.. one number has an effect on another. there is a sample report on this page as well so you have an idea of what it would look like.


and on the bottom left click on oil analysis.

******** here is some information that might help you located the noises for your self, this is going to be a cut and paste, happy hunting and wish you luck...

First thing you need to do is spend 20 bucks for a cheap stethoscope at the auto parts store or if you are going to do this a lot get the electronic ones from Steelman for about $160.

But, possessing human nature, you will convince yourself that a hose stuck in your uneducated ear will do just as well. No sense in arguing with you that the whole idea is to be able to discern infinitesimal changes in direction and intensity that require the use of two somewhat experienced ears AND the right tools.

So stick your dumb ol' hose in your stupid ol' ear and we'll start with some clues.

Remember that diagnosis of engine noises is nothing more than splitting possibilities down to only one

First off, eliminate all of the accessories like the alternator, power steering pump, A. C. compressor and vacuum pump by removing the belts one at a time. If the noise is gone, of course the problem is a belt driven accessory. If the naughty noise is still there you should be able to hear it more clearly by not having the accessories whirring away.

If the engine has a carburetor instead of fuel injection it probably has a mechanical fuel pump mounted to the engine. Before the engine gets too hot, put your hand on it. If it is making a noise you should be able to feel it.

Try to track the noise down with the stethoscope tip or the end of the hose suckered onto the engine surface, sealing the end. Spend a full ten minutes putting the hose all over the engine, not just where it is loudest. Try to envision the parts moving inside the engine. You are training your ear, not just listening, so don't get in a big rush except to be sure that the engine doesn't overheat. A trained ear can tell you which piston is slapping or which rocker arm is clacking from outside the engine so if you come out from under the car proudly saying, "it's the bottom end" get your dumb-ass back under there until you can tell me it's coming from the oil pump or the 3rd piston back on the driver's side or the flywheel or the camshaft.

Rod knocks are loudest at higher speeds (over 2500 RPM) Feathering the gas pedal may result in a distinctive back rattle between 2500 and 3500 RPMs.

Bad rod knocks may double knock if enough rod bearing material has been worn away allowing the piston to whack the cylinder head in addition to the big end of the connecting rod banging on the crankshaft rod journal. It will sound like a hard metallic knock (rod) with an alternating and somewhat muffled aluminum (piston) klock sound.

Wrist pin knock in modern engines is very rare today but is a favorite for the misdiagnosticians.

Determining which cylinder contains the noisy parts may be aided by shorting out the plug wires one by one with a common low voltage test light. Now you won't get the bulb to light up but it is a convenient way to short the cylinders without getting zapped or damaging the ignition coil.

Attach the alligator clip to a convenient ground, away from fuel system components, and pierce the wire boots at the coilpack or distributor end of the wire.

If the noise is changed when the plug wire is shorted to ground, you can figure that the problem is in the reciprocating bottom end parts. (piston, wrist pin, connecting rod or connecting rod bearing)

The reason the sound changes is that when you short the cylinder plug wire you are stopping the combustion chamber explosions that are slamming the piston downward making the inside of the big end of the connecting rod bang against it's connecting rod journal. Or in the case of piston slap, no explosion changes how the piston is shoved hard sideways against the cylinder wall.

If you get a change in the sound when you short a cylinder out it may become moot as to what the problem is because the oil pan and cylinder head must be removed to correct the problem. [Generally speaking, an engine with damage to reciprocating parts (pistons, rings, connecting rods, wrist pins or rod bearings) and more than 70 thousand miles is not cost effective or risk free enough to attempt to repair. Replacing a crankshaft, for example while the rest of the engine has 70k perfectly maintained miles on it is risky enough but whatever killed the crank has scored the rings and packed the lifters with debris and smoked the piston pin bosses etc.]

If the sound doesn't change, look at parts other than the reciprocating ones. In many cases of rod-knock or piston slap, more than one is banging so even if you eliminate the noise from one rod the other one will still be a-banging away with a different, more singular tone.

When the engine is cold, the aluminum piston is small in comparison to it's iron cylinder. Therefore the rather hollow slapping noise will be loudest first thing in the morning. After the engine warms up, the aluminum piston heats up faster than it's iron cylinder, cutting down on the excessive clearance between the piston and cylinder wall.

So, the test is this:

First thing in the morning, start the engine up and run it for 15 seconds while you listen carefully and memorize the sound and it's intensity. Shut it down quickly, pull the spark plugs and put two squirts of motor oil into each cylinder. Reinstall the plugs, fire the engine up again and listen.

If you have piston slap the noise will have been greatly reduced or even eliminated…..for 15 or 20 seconds that is, and then your nightmare noise will come back like a Marine Corps marching band coming toward you in the parade.

Diagnose Noises with a timing light?

Valve train noises occur at half of crankshaft speed so even if your ear can't tell whether the noise is happening at 700 rpm (raps per minute) or only 350 rpm, your eyes can. Hook the timing light to any one cylinder and watch the flash illuminate the timing mark. Stare at it for a while and see if the flash jives with the knock. If it does, then it is more likely to be rocker arms, pushrods, lifters, camshaft, cam bearings, timing chain and gears. If the noise seems twice as fast it is probably in the crank, mains, rods, rod bearings, wristpins and pistons.

well people, i hope this helps.

bob in jville, fl.
Member STLE
Lubricant Specialist

<font size=-1>[ This Message was edited by: bobistheoilguy on 2002-01-13 19:40 ]</font>
See less See more
blackstone labs does oil analysis for $20
Haven't heard the noise in my Bullit, it has 2600 miles on it. However, I hear it in my 1995 Taurus wagon with 110,000 miles on it. Writing if off to the 87 octane gas I use. BTW I use 93 octane in the Bullitt and haven't had any issues. :-B
21 - 25 of 25 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.