ADC Lehman 136N knocking...

[Ben]

http://youtu.be/-zOcUqn29hg

Anyone know what the knocking is? Does not sound good at all... ?

 

[kchace]

It sounds too slow and a bit random to be the engine. I'd check damper and external components like water pumps and alternator ( though it sound too heavy to be the alternator)

Ken

 

[Capt.Bill11]

You can cut out one cylinder at a time to see if that makes any difference.

 

[Ski in NC]

Could sound be coming from air intake? Heard something like that when there was a sticking valve. Go listen to air intake. Also check belts, listen there. Listen at transmission too. Try to isolate location of the sound.

 

[Xsbank]

Just make sure you have no loose clothing or similar when you go leaning over the engine.

It sounds pretty good without the clunk. I think its some peripheral. Let us know if you can find what part of the engine? Does it change with rpm? Does it change if you put it in gear?

 

[Manly Q.]

Hi Ben.

To this untrained ear it sounds like something banging on the inside of the sump, the hollow dull thump of contact with the side wall of the sump.

Does this engune have a filter head on the oil pick up in the sump, could it have broken a locating stud and be rotating with the engine revs. Can you put your hand on either side of the sump and feel if the knock in down that low.

Sorry that is all I have.

Regards.

David.

 

[Ben]

OK, more detail.

1. I've not yet engaged the transmission.
2. Seems to be occurring high and forward.
3. Seems to be of a pitch of light metal hitting, like aluminum valve cover as opposed to iron block.
4. I have a loose ground wire (believe to be house bank, need a new connection crimped on) on one side of the engine that needs re-connection, but not sure this would be a factor.
5. Next step, I will pull the valve cover and inspect.
6. Could injectors be a factor? Replacing injectors, I've never done, and I'd really need guidance on the cautions and technique. Not believing this to be the source, but not counting it out either.

Thanks for all the guidance!

 

[Ben]

Just make sure you have no loose clothing or similar when you go leaning over the engine.

It sounds pretty good without the clunk. I think its some peripheral. Let us know if you can find what part of the engine? Does it change with rpm? Does it change if you put it in gear?

Good advice. I don't want to be eaten by my engine. I like my fingers.

It reduces in frequency with greater RPM, the sound is not consistent. It does not occur with a ratio of frequency to the turns of the motor (as in a 6-cylinder motor - at 600 RPM, I'd expect about twice a second, but seems more random)

 

[bayview]

Use a section of hose or a stethoscope to localize the source. Listen carefully at the front end.

 

[bayview]

does it follow engine rpm?
don't start replacing things until you are sure. Not likely to be injector or wiring. Loosen one fuel line at a time and see if the sound changes differently on one cylinder.

 

[AusCan]

Doesn't sound like piston slap or con rod. That's the good news.

A mechanic's (or doctor's) stethoscope may help locate where the knocking is coming from. I've also used a screwdriver held against the block with the handle on your ear to transfer sound.

If it was something (valve or rocker cap) bouncing around under your rocker cover, I would expect you'd be able to feel it.

A long shot but - Does a slight pull of mechanical kill switch make any difference to the noise?

 

[RNL]

I agree with Ken as it sounds somewhat random. Have you checked the motor mounts?

 

[Ben]

I agree with Ken as it sounds somewhat random. Have you checked the motor mounts?

Motor mounts okay, this sounds like from inside the engine. Will scour a drugstore for a stethoscope today.

Thanks.

 

[rardoin]

Motor mounts okay, this sounds like from inside the engine. Will scour a drugstore for a stethoscope today.

Thanks.

I recommend looking at a parts store for a mechanic's stethoscope rather than a medical steth.. The mechanic's stethoscope will have an aluminum probe of 8-12 inches on the business end that can be touched on various areas of the engine that would not be accessible with the bell/diaphragm of the medical variety. It will more efficiently carry the sound by conduction up the probe.

 

[DNT99611]

knocking

I have used a wooden scrub brush or a large wooden dowel, cut off piece of a broom handle, to chase down strange sounds. I found if you are wearing a pair of ear muffs at the time it works even better. I have been able to easily pick out the leaking valve on fluid pumps this way.
David

 

[SCOTTEDAVIS]

In a pinch a long screwdriver with the handle held tight to your ear and the tip placed at points on the engine you want to investigate will also work very well.

 

[jleonard]

In a pinch a long screwdriver with the handle held tight to your ear and the tip placed at points on the engine you want to investigate will also work very well.

Hey I've done that too. Seemed to work for me.

 

[Xsbank]

I can't remember if the old Clamcrusher has a timing chain or a set of gears? If it's a chain, it could be that the tensioner is shot allowing the chain to hit the cover? Like I said before, the engine sounds good...Belt loose and hitting something? Everything else is attached and would make a rhythmic knocking if damaged.

 

[Ski in NC]

Gear drive, no chain.

 

[kchace]

Yeah this one is hard to diagnose at a distance. At 600 rpms the crank is turning 10 times a second and every cylinder fires 5 times a second. This sound is nowhere near that fast. To me that rules out anything to do with pistons, rods, injectors, etc. i agree that maybe something is loose inside and bouncing around?

I've never heard a broken crank. Wonder if that's possible?

Ken

 

[Ben]

Yeah this one is hard to diagnose at a distance. At 600 rpms the crank is turning 10 times a second and every cylinder fires 5 times a second. This sound is nowhere near that fast. To me that rules out anything to do with pistons, rods, injectors, etc. i agree that maybe something is loose inside and bouncing around?

I've never heard a broken crank. Wonder if that's possible?

Ken

I did the same math, and comforted myself. I've been off-boat a few days, so will go down this week and do the screwdriver check and pop the valve-cover for a look. After that, I'll call the mechanic. Want to have in mind the problem before the mechanic is on site. The good news is that the tone sounds tinnier than thumpy. So the valve cover pull is a good first look. I can go that deep, but after that, I start getting a little worried.

Thanks!

 

[Capthead]

I had a harmonic balancer go bad on my diesel truck and it made a very similar noise when it started. It got worse in time and if that is the problem change it as soon as you can. If it turns and gets off balance they have been known to break the crank.