6.2 knocking sound...

[Rytari]

i know, there is lots of questions here about it, but i really didnt find anything for me...

i have some not so nice, knock knock knock noise in my 6.2... at idle its wery quiet, but even little increase of rpm and it can be heard almost anywhere :)

so, i think knock comes every rpm, but i cant locate it, cant say if it is up or down, left or right side of the block.

some more black smoke coming when driving 55-65 mph than previously

no loss in power or anything else like that.

change new injectors, not any difference to knocking sound...

some of the pushrods didnt rotate freely, i took and cahnge those, not any help...

so.. next to do?... i cannot open oilpan when engine is in the car...

[john8662]

Does your engine have the dampened front pulley on it, or the pressed steel version? This will be bolted onto the front of the harmonic balancer.

If it has the rubber version it's possible that it's failed, you'll be able to remove the drive belts and check it fully (by tugging to one side or the other, trying to rotate it).

Other things that cause a knock are a bad flexplate (or cracking flexplate) between the engine and the transmission. It's also very possible that a missing, or loose set of transmission bolts on the torque conveter are causing the noise.

[Rytari]

i didnt find anything wrong in my flexplate... and i have steel pressed pulley...

i try to listen the sound and realise it comes from left side head. is it any good way to see if some lifter can cause the sound.. im sure it comes from front of the engine, around #4 cylinder. i open valve cover and change 4 lifters... those that i took out looked just like the ones i put in.. and nothing happend, noise is still there.

[Robyn]

Oil pressure good??

Try running at as speed where noise is present and crack open the injector linesone at a time to see if the noise goes away.

If noise goes away then it could be a bad injector or a wrist pin or possibly a cracked piston.

There is also a real possibility if the engine had been set idle for some time that some carbon fell off an intake valve and is taking up all the clearance between the piston and the head and causing the knock.

There is only about .035" between the head and the piston at TDC.

Try checking the injectors by cracking the lines one at a time and lets us know.

Also is the knock runing at piston speed or cam speed???

Best

Robyn

[Rytari]

i hope its not the injector cause i chaged new ones 2 weeks ago and noise didnt make any difference.

noise is present almost at idle to somewhere over 2500rpm

it feels like its not piston speed, i try to calculate it... something like 440 times per minute at idle... as increasing rpm the knocking sound will not increase at same speed... i mean if it less tha one knock in second at idle its not still more that 2 knocks at 2500 rpm..i dont really know the correct rpm of the engine.. but i use the "feels like tachometer" so its should be cam speed.

previously at summer noise was littlebit smaller... i think carbon on top of piston doesnt act like that... i think...but my intake really is quite dirty because theres no cdr valve in, just rubber hoe from oil fill tube to side o intake.

ill try to open lines one at time and see if it makes something.
just getting a feeling that those engines dont like my way of driving.

[Robyn]

How long was the engine sitting before you installed it in your Caprice??

A 6.2 or 6.5 that has sat for a period of time can have carbon from the intake valves come loose and fall into the cylinders.

As I mentioned before, this will make a lot of noise.

You can try opening the intake (Remove filter) run the engine at around 1500 RPM and using a suitable spray device add a fine mist of water to the air flow. (Dont drown the thing, just add a mist of water)

A small spray bottle like those that window cleaner come in will work.
Direct the spray to the different cylinders from front to back.
(You can see the runners in the intake plenum)

If its carbon on top of a piston, this may help loosen and dislodge it allowing it to blow out the exhaust.

With fresh injectors that pretty well eliminates them from the picture.

At this juncture there is little more that can be done without investigating whats inside the beast.

Robyn

[Rytari]

i havent installed it.. somebody fitted it there... its been there maybe 10 years or so...

[nunderwier]

Ya I had a knocking sound 6 months ago. Got to work just fine but when I tried to go home thought something snapped in the engine or vales. After a lot of looking it turned out that one of the glow plugs broke fell through to the top of the piston. On the other hand one side of my engine is semi rebulit. :)

[deepseeman]

I just developed a knock myself. its coming from the rear passenger side. did an engine flush and used 50w and it didnt silence it at all. noise is most noticeable/loudest right at the first shift point. I will try the injector trick tomorrow. Any other ideas?

[deepseeman]

ok, so I researched all the threads on here and did a little investigation on my motor. its not a flexplate, nor injector and I did the tranny fluid clean out thing and put in a 50w oil. I still have a knock. its not so noticable when the motor is cold, but as soon as i get off the freeway any mid range to low rpm really produces the knock. Any ideas? i dont want to run her and make it worse. help.....