Dull knocking

Have had this for a little while but keep forgetting to ask, when i first start up mmy car after a couple seconds it starts doing a dull sounding knocking and gets quieter at higher rpms but pretty sur it never really goes away, what could this be? fairly loud but not obnoxious, ive heard of loose flexplate; or maybe bent rod(never gone over 3500 rpms so cant see it being that), but im really new to the I6 stuff so what do i know :| If any one got any idea feel free to say, THanks, Lee

does it go away once warmed up?

my 4.3L in my truck (pulled at 180K) and th replacement 350 I put in it (honed and re-ring a surface rusted bore) both knock a little when cold. Just a loose fit on the piston until they warm up and expand.

if it knocks the whole time I would be a little worried though.

8) a dull thud depends on where it is coming from. get yourself a long piece of broom handle, and hold one end next to your ear, and the other where you think the sound is coming from. a bottom end location often times indicates a main bearing knock. and since it is a dull sound and goes away with higher rpms, that would be my diagnosis over the computer, without hearing it in person. a sharp double tapping sound is usually piston slap if it is in the middle of the block, or a rod knock if at the bottom of the block. if you get a sharp double tapping sound that goes away when the engine warms up, then you likely have a piston slap issue.

I also have a faint ticking sound coming from my engine, that I just noticed within the past couple hundred miles or so after I had no oil pressure following an oil change and had to manually prime the pump to get it working again.

The sound may have been around before, but I do not recall noticing it. I fixed a noisy PCV valve at the same time, which may have masked this sound. When using some old rubber tubing I cannot pinpoint the noise to the valvetrain area, but have not tried the broomstick method as mentioned above. Adjusting the valves didn't seem to change it. I hear the sound it seems about twice a second, so not too short but not too long between.

But being that it was an oil pressure issue that may have started it, I'm thinking it might be the main bearings. Especially since I believe I ran it up to a minute without oil pressure following that oil change. I still get good oil pressure, same as it was before the incident. Regardless, unfortunately I have no where near the desire nor the money to have it rebuilt at the moment (especially if I don't know for sure what's going on, or how serious it is), so I don't know what to do.

I also haven't been able to distinguish for sure if it goes away after being warmed up, but I think it may be at least quieter.

Wondering if we have the same issue going on.

8) given the loss of oil pressure, i would say then that you have, without puling the pan and checking the main bearings, a main bearing knock, and perhaps a spun main bearing as well. the ticking sound is probably a lifter that isnt pumping up properly. as for losing the prime in the oil pump from changing oil, that indicates to me an oil pump problem. now it may be possible that there is no bearing problem, and that the oil pump itself may just be loose. either way you are going to have to drop the pan and fine out before bad things start happening.

'Could be simple water pump or fuel pump knockin but my dull knock usually followed with oil light ghosting at idle and then louder multiple knocks with the magic smoke escaping engine 8) . Any audible dull knock can be cause to worry but also may not be ready to blow'. Keep your revs low and take it easy a worn six may last a long time. Troubleshoot, repair or replace and keep ridin'...

powerband":3r9h4caa said:

'Could be simple water pump or fuel pump knockin but my dull knock usually followed with oil light ghosting at idle and then louder multiple knocks with the magic smoke escaping engine 8) . Any audible dull knock can be cause to worry but also may not be ready to blow'. Keep your revs low and take it easy a worn six may last a long time. Troubleshoot, repair or replace and keep ridin'...

Click to expand...

8) good information, which is why we need to know where the knock is coming from.

I got the ticking noise also but it doesnt bother me cuz i figure its just a lifter, i always get good oil pressure(45psi cold and only under 30psi when im in traffic jam and runnin bout 200 degrees F).

Pretty sure my knocking gets quieter when hot, we actually have a thing like doctors have to listen to your heart but at the end of the thing is like a long needle that u touch the engine to listen, cant recall what its called. I will use that today, will reply what i find out.

merccomet":23clg5vb said:

I got the ticking noise also but it doesnt bother me cuz i figure its just a lifter, i always get good oil pressure(45psi cold and only under 30psi when im in traffic jam and runnin bout 200 degrees F).

Pretty sure my knocking gets quieter when hot, we actually have a thing like doctors have to listen to your heart but at the end of the thing is like a long needle that u touch the engine to listen, cant recall what its called. I will use that today, will reply what i find out.

Click to expand...

8) its called a stethoscope.

Another possible source Jack has often mentioned (and comes up more often than you'd think) for 'knocking' are dents in the oil pan making even slight contact with part of the crank assmbly...not much extra space in the pan, so it doesn't have to be a big dent, but stethoscope, stick, screwdriver, etc to the pan should ID that one....and occasionally exhast leaks can sound like a lifter tick (just not a knock)...I had read somewhere before that overfilling oil on the straight sixes can cause 'too much' sloshing in the pan and derpive the lifter gallery...causing ticks : ...not sure where I heard that one. Good luck

Thank you guys so much for your input, for both him and me. I do get good oil pressure, around 35-40 psi immediately after starting the engine.

I have had exhaust leak issues in the past, and despite resurfacing the head and installing a new manifold, I am not completely sure it is gone since I believe I smell it sometimes (I always drive with a window open for that reason).

How do you check for exhaust leaks?

-- Edited in below --
I went out and bought a mechanic's stethoscope (essentially ear buds with a metal rod at the end). I started the car and could hear the faint ticking noise, and stuck the stethoscope against various parts of the engine but could not hear that noise from them (Is the noise heard fainter through the stethoscope?). I tried listening to the water pump, next to each spark plug, at the bottom of the block at each cylinder, and at the top of each port of the exhaust manifold. I heard a little bit of noise in the middle of the exhaust manifold, where I had the leak before, but not sure if that was the noise I've been hearing.

Are there specific places I should be sticking the stethoscope to test? One thing I forgot to check was against the oil pan. Tomorrow I will try that and also try some old rubber tubing to the ear again.

Thanks rbohm, that name come to mind but some reason i thought the mechanic one may have had a different name.

I do have a good dent in the front of the oil pan on the lower part of the pan (not sure how to describe it... its at the same level as the drain plug) never came to mind b/c i cacnt recall hearing it when i first got the car, a few years ago.

Canary94GT":3begsus0 said:

How do you check for exhaust leaks?

Click to expand...

Exhaust shop guys use a stethoscope with nothing on the end...just an open hose, and 'carefully' move it around in close on the exhaust manifold w/o melting or burning it or yourself...imagine they're targeting the air percussion.

merccomet":3begsus0 said:

I do have a good dent in the front of the oil pan on the lower part of the pan (not sure how to describe it... its at the same level as the drain plug) never came to mind b/c i cacnt recall hearing it when i first got the car, a few years ago.

Click to expand...

Yeah, not sure why it would all of a sudden make racket...maybe took another hit somehow...just hoping for your sake it's something that simple or similarly less serious than rod/bearing/piston knock...Good luck!