knoking sound from engine

[stm]

Hi, all!

I hear a "knocking" sound on a cold engine at idle speed.

Sound have "metallic" tone, crispy and very loud. It came from lower part of engine, maybe from oil pan and/or main pulley of crankshaft. Oil pan is resonate and amplify this sound. If i stand behind Bronco in 10-20 meters, i hear only this sound - it's louder, than everall engine sound. Frequensy of this knocks is same as rpms of engine.

After 30-40 min of working at full load (in motion) and fully warming up it sound is more quiet, almost inaudible...

Engine have this sound about 10 000 miles or more, and have not stucking or abnormal accidents.

It's not a airpump - i check it...

What part of engine can making this sound? Timing chain and sprockets? Rockers or valves? Crank liners?

 

[Bully Bob]

Hi STM.,

Pull 1 spark plug wire at a time, while eng. is idling. If/when noise goes away, or gets very weak, ..... that will tell you which cylinder has an issue.

Bad news is., it's probably a rod or wrist pin. OR it could be "piston slap"

Let us know if the noise DOESN'T go away doing this test.

 

[miesk5]

yo,

As Bob advised on pulling a plug, and then another...

Here is Noise Overview, General

Source: by southernwheels.com

http://www.southernwheels.com/Feb_04Frame1Source1.htm

TSB 94-4-14 for 5.0 in 87-90 Bronco, E 150, E 250, F 150, F 250; engine miss, spark knock

Source: by Ford via Chilton http://content.chiltonsonline.com/TSB/displayTSBHandler.ashx?assetID=35890&key=6kAUBD5BruOJf%2f3tgozUqjXM3RdbjcQqW4sVWiE%2fp2IojfpfKqM07dr61%2bQAWHtTg1LwFOC3QQe2onHMrJq7ubrB0CiSaMcUhXocK0rButfsAXoCY2rOAJHR6eWXS1Bqgsj3HYNBgwCFv3nI%2flywSA%3d%3d

Tips to Avoid Lean Conditions TSB 91-8-13; "...Rough idle, hesitation, poor throttle response, induction backfire and stalls during cold start/warm up may be caused by the poor volatility of some high octane premium grade unleaded fuels (91 octane or higher (R+M)/2). When compared to regular grade unleaded fuel (87 octane (R+M)/2), high octane premium grade unleaded fuel may cause long crank time.ACTION: Use a regular grade unleaded fuel in all vehicles, except where a premium unleaded fuel is recommended in the Owner Guide. If lean air-fuel type symptoms are experienced, determine the grade and brand of fuel used and offer the following service tips. Advise those using a higher octane grade fuel to switch to a regular grade unleaded fuel. For those using a regular grade fuel, advise them to try another brand. Do not advise using a higher octane unleaded fuel than is recommended for that specific engine. Ford engines are designed to perform best using a high quality regular grade unleaded fuel. Only advise using a higher octane unleaded fuel to avoid potentially damaging spark knock or ping, but do so only after mechanical fixes are ineffective. NOTE: ALL UNLEADED GASOLINES USED SHOULD CONTAIN DETERGENT ADDITIVES THAT ARE ADVERTISED AS HAVING "KEEP CLEAN" OR "CLEAN UP" PERFORMANCE FOR BOTH INTAKE VALVES AND FUEL INJECTORS..."

Source: by Ford

 

[Seabronc]

Another possibility is a loose spark plug wire at the plug. I have had this happen to me after changing plug wires and didn't have one of the plug wires properly seated. I was sure it was a rod until I happened to be pulling wires and found one loose. The noise was generated by the spark jumping the gap from the wire to the plug.

Hope it is something simple, because the alternative can be a lot of work.

Good luck,

>-

 

[stm]

I checked for test with spark plugs. Nothing is not changed. When i remove spark plug at time, engine is slightly changed overall sound tone, normally responded for loose 1 cylinder per time, but this knock was stayed.

Spark on at each wire is mighty and powerfull. I take discharge over 1000 times in this operation)))

And it's not spark plug disconnection - i check all spark plug tips.

Each cylinder have "ignition" and combustion.

 

[Bully Bob]

"I take discharge over 1000 times in this operation "

--- How funny...!! :lol:

Ya., too many jolts fr. a good coil will make you cross-eyed :wacko: & turn your ***** blue. /emoticons/[email protected] 2x" width="20" height="20" />

A better method is heavely insulated gloves, a wire puller tool, or shut the eng. off between cylinder tests. >< <'>

Being the knock didn't go away on one cylinder (may be a good thing)., a collapsed/sticky lifter may be the culprit. A fuel pump can make noise..?

Do you have a camera with video & SOUND.? (that would help)

Do go over M5's source list.

 

[stm]

A better method is heavely insulated gloves, a wire puller tool, or shut the eng. off between cylinder tests.

Gloves (standard cotton gloves for repairing) was not helpd. I used pliers, but it constantly "pierced" to ground... So short air interval to other grounded parts. I haven't shut engine for better understanding of difference between sound of full load and sound of "-1" cylinder.

Being the knock didn't go away on one cylinder.

??? Maybe i something don't understand or wrong wrote? No one cylinder, but engine worked on 7 cylinders per each time. So, sound don't removed for each time... I think, that engine can't work on only 1 cylinder...

a collapsed/sticky lifter may be the culprit

Why sound comes from lower part of engine? Maybe i can't catch sound normally?

A fuel pump can make noise..?

No. Pumps are placed in fuel tank and under the frame....

Do you have a camera with video & SOUND.? (that would help)

Yes, i will make a movie tomorrow.

Do go over M5's source list.

Aha, i alrady studying this manual now...

By the way, M5 - greate guy. For any users, for stupid questions, again and again, he post extremely detailed response. My gratitude to him!!! Where he find so rare manuals, schemes?))

 

[Bully Bob]

Sounds do "transmit"

Yep.., M5 is "Da Man.., YO" ^_^ /emoticons/[email protected] 2x" width="20" height="20" />

"??? Maybe i something don't understand or wrong wrote? No one cylinder, but engine worked on 7 cylinders per each time. So, sound don't removed for each time... I think, that engine can't work on only 1 cylinder..."

No.., you got it right.... while testing each & all 8 cylinders., if the noise went away, with wire off any of the spark plugs.........., that would be the cylinder with an internal problem.

Seeing the noise didn't go away....the issue may be in the "top-end" as I stated.

 

[stm]

Sorry for delay. Hard working days was at week...

It is movie for working of my Bronc engine.

I try make it more detail.

 

[Bully Bob]

Hi STM.,

Hard to tell fr. the video but it sounds to me more like a collapsed piston.

What this means is the sides of the piston skirts are worn/tapered a bit allowing piston slap. (Piston flopping against the cylinder wall)

If that's the case, this is not critical., just annoying.

 

[stm]

Ok. Thanks. I'll hope for that.

 

[Bully Bob]

Less likely but a possibility.., I've had waterpumps, idler pulleys, even alternators make a racket.

A quick test is to pull off the serpentine belt., start up & see if noise still exists with those peripheral accessories NOT moving.

Probably shouldn't let it run very long W/O the belt though.

 

[stm]

Ok, roger that. I'll check it at next weekend.