Cold start knock video

[19jacobob93]

http://youtu.be/u0nWJQ33l0A - noise can be heard 0:20 onwards

Finally got the video uploaded.
Only knocks on some mornings, mostly the cooler ones. Sounds like it is coming from the bottom end but I'm not certain, it is loudest under the car (but so are the lifters for some reason) and it can be heard inside the cab.
It goes away after about a minute or less and the engine runs quiet when warmed up, no knocks will be heard on start ups later that day.
Running recommended 10w30 with 1/2 bottle of Rislone added

 

[Lubener]

Try an oil/filter change and leave out that rislone. I heard too many times of people using cleaners on a dirty engine and causing grief. Deposits loosen up and might block oil passages. I know of two who locked up their engines. Put a manual oil pressure gauge on it and verify that the pressure is at specs, after the oil change. Sounds to me like main bearings.

 

[19jacobob93]

Originally Posted By: Lubener
Try an oil/filter change and leave out that rislone. I heard too many times of people using cleaners on a dirty engine and causing grief. Deposits loosen up and might block oil passages. I know of two who locked up their engines. Put a manual oil pressure gauge on it and verify that the pressure is at specs, after the oil change. Sounds to me like main bearings.

It started to do it last interval before the Rislone which I added to clean out the lifters.
The engine is pretty spotless inside now and the oil that is in now has been in for nearly 3,000km and it has only just started to turn a yellowy amber colour so the internals are clean at least.
I will try the oil pressure test, although there are no other oil pressure related issues which are rare on these engines even after massive amounts of abusive mileage. I said previously I know someone with the same car/engine he uses as a beater work car, it has 960,000km on the engine and it has had nothing but oil and filter changes, runs great too. I just can't see the bottom end knocking after just 210,000 but maybe there is an oil blockage somewhere

 

[spasm3]

Can't tell from the video. perhaps its piston slap. One the engine has been warmed and has not really cooled off internally the piston is still warm and a bit bigger. But i agree to try a different filter first.

 

[friendly_jacek]

Originally Posted By: 19jacobob93

It goes away after about a minute or less and the engine runs quiet when warmed up


this is the definition of a piston slap. welcome to the club.

 

[SwampSurvivor]

Sounds like a piston slapper!

 

[4wheeldog]

I am going to take this in an entirely different direction......I think you have an exhaust leak......Probably at the exhaust manifold/head gasket.

If you watch the exhaust, when listening to the noise, there is a rhythym to the exhaust in time to the noise. Or.....I am imagining it. But it is worth checking. It does not sound like piston slap to me.

 

[spasm3]

Originally Posted By: 4wheeldog
I am going to take this in an entirely different direction......I think you have an exhaust leak......Probably at the exhaust manifold/head gasket.

If you watch the exhaust, when listening to the noise, there is a rhythym to the exhaust in time to the noise. Or.....I am imagining it. But it is worth checking. It does not sound like piston slap to me.


Thats a good thought , maybe even a crack in the manifold.

 

[Pontual]

The "flap-flap-flap", is piston slap, to me. Try cleaning the ring pack before you get too much scuffing and polish the cylinder walls. Do an UOA to see how much alluminum and iron comes from piston skirts and cylinders.

 

[horse123]

Originally Posted By: 4wheeldog
there is a rhythym to the exhaust in time to the noise.


Yes. That's generally how any engine related noises sound. You're not going to have randomly spaced noises coming from the engine itself unless it's seriously messed up.

 

[aquariuscsm]

I can't tell from your video,you have your camera in the wrong spot. Make another cold start video with your camera in the engine bay.

IF it's piston slap,try an oil change of PYB 10W30 and an MC oil filter and we what happens.

 

[4wheeldog]

Originally Posted By: horse123
Originally Posted By: 4wheeldog
there is a rhythym to the exhaust in time to the noise.


Yes. That's generally how any engine related noises sound. You're not going to have randomly spaced noises coming from the engine itself unless it's seriously messed up.


Not my point.....The exhaust changes VISUALLY in relation to the knock noise.....As if a single cylinder is being effected, and the exhaust is leaking, once per revolution. Watch it again.

 

[OVERKILL]

Originally Posted By: Pontual
The "flap-flap-flap", is piston slap, to me. Try cleaning the ring pack before you get too much scuffing and polish the cylinder walls. Do an UOA to see how much alluminum and iron comes from piston skirts and cylinders.


The cleanliness of the ring pack is irrelevant to the presence of piston slap, not sure why you've decided to draw that correlation

Many GM engines slapped from new due to having short skirts. Ford used coated skirts to mask the problem on their short skirted engines but some made noise anyways. That's the result of the move to shorter pistons for lower drag and bulk-fit pistons vs hand fit.

And a UOA isn't going to tell him anything about what you are positing here unless something was self-destructing and even then it's a [censored] shoot.

 

[SnowDrifter]

You could also try a 5w30 or 0w30. I ended up moving to 0w30 in my Subaru as I found that was quietest.

See if you can use a stethoscope or a long screwdriver to determine where the noise comes from

FWIW I've found using a block heater on a timer 5 hours before starting seems to get things warm enough that the sound mostly goes away

 

[19jacobob93]

Thanks for all the replies guys. I have spoken to someone with a bit of knowledge on these engines and he reckons he knows what it is after watching the video.
Because the crank is like 6 foot long on this engine (lol) the rod bearings 5 and 6 can suffer from oil supply issues if the engine has had a hard abusive life (which mine probably has being an ex rental car with 20-25k OCIs in the past)
It sounds like one knock so I'm guessing my issue is oil supply to rod bearing number 6.
He said he has seen it a few times and thinner oils tend to get lost on their way through the crank, and a thicker oil is needed to stay there.
He recommended 15w40 or 15/20w50 which I have all 3 so I will do a trial and error with each one in my up coming oil changes

 

[SnowDrifter]

How hard is it to drop the oil pan? You could always pull it down, check clearance of bearings and order appropriately sized bearing halves. It's not perfect as it's not a full rebuild but it's fairly easy to do and might extend some life

Look up a product called plastigauge for measuring bearing tolerances if that's anything you're interested in.


As far as an oil supply issue: I wonder if a high flow high pressure oil pump could help with this scenario. High flow pump with a higher bypass pressure

 

[friendly_jacek]

OP, keep us posted how the thicker oil goes.

 

[hpb]

It's hard to tell from there - under the bonnet would be a better place to record it, maybe. There's definitely a knock there though! While I've never heard the explanation given to you before, it's certainly easier to try some different viscosity oil than replace bottom end bearings. And as I said before, use a long screwdriver to see if you can isolate the noise. Good luck with it mate!

 

[19jacobob93]

I'm not sure how hard it is to drop the pan on these or if it would be an engine out job because these 4.0 inline sixes really are a big block at least in terms of length.
I would be really surprised if there was an issue with the bottom end because I've never seen or even heard of bottom end problems on these engines even in excess of 1,000,000km on them! Saying that not all of them were rental cars running 20k+ OCIs!

 

[19jacobob93]

I will report back with my experiences each oil change to a different grade.
The part that stumped us is that the noise only happens on the colder mornings closer to freezing, which is when the oil is at it's thickest, so surely if that's the case a thicker oil would be even worse? But I guess theres only one way to find out