Rod knock. When you rev and let off the sound lessens during the over run. Classic rod knock. However, get a mechanics stethescope to be sure it is internal to the engine, not something like a belt pulley with a missing chunk...

 

Thank you for your reply I appreciate it, it’s recently been getting worse but only really at idle, it’s started knocking more on idle than what it done at first, I’ve just been putting it down to Vanos rattle, but since doing that nothing got better, engine only has 77k miles and good compression on all cylinders, I’ve always kept on top of oil and changed every 4-5k.

 

I’d also like to add I’ve put over 10k miles on the car with it making this noise, I mean it’s got worse on idle recently like I said but In terms of revving the car while at a standstill and if I steady accelerate in 1st/2nd/3rd the rattle comes on around 2k rpm, the car has been doing that ever since I got it, and since then over 10k miles have been put on it, the reason I’ve not done anything about it is because 1. I put it down to Vanos rattle 2. The car drives perfectly fine plenty of power there accelerates just how it should I also mainly drive it in drive and when In drive you very rarely hear it it’s only really when I put it in manual mode to drive it harder that I start to notice and hear the noise, again thank you for you help I will take it to my mechanic, has anyone else got an opinion on what this sounds like, thank you.

 

So you bought the car with this noise from the beginning and thinking it was VANOS rattling. Have you ever heard the vanos rattling before? It must be faster frequency than rod knock like what you're having.
Did you change the oil and look at the filter -- see any metallic flakes in the dirty filter? Maybe it's time to remove the filter and take a look. If it looks clean then you can put it back. It indeed it's the rod knock, then the bearing has been beaten quite thin by now. What is the normal high rpm in your drive?

 

Measure the hot engine oil pressure at idle. It sounds like one of the worst cases of bad bearing.

 

Sounds exactly like rod knock unfortunately

Okay thank you both of you, I appreciate it, how would I go about fixing this then what parts do I need is it rod bearings, is it a hard job to do? I know it involves taking the oil pan off etc.. how much would it cost diy and would this have damaged any other components in the car?

 

Sounds exactly like rod knock unfortunately

 

I've done it with the engine out of the car. Then it's very easy. Ofcourse taking the engine out is overkill for this job. IIRC it should be --> support engine from top, remove subframe, remove oil pan, and then you can get to work. It's a dirty job and not something you do in half an hour. If you DIY, take your time. Parts needed: new bearing shells, new rod bolts (don't reuse the old ones), new oil pan gasket. If you DIY it will take some time and work but it won't cost you a lot.

That is in case your crank is still intact. If it isn't, you're probably in for a lot more ££.

 

Assuming the crank is OK. I'd want to find cause.

Thank you mega for the information that was really useful I will look into getting the parts to do the job. Also to mega and RRR how do I know if the crank is okay how would I tell that and what do you mean by you would want to find cause? Thank you for your help

 

Assuming the crank is OK. I'd want to find cause.

 

I mean I would want to find out why bearing failed on a 77k mile engine.
You could take pictures of the crank journal and post here to start..

 

I mean I would want to find out why bearing failed on a 77k mile engine.
You could take pictures of the crank journal and post here to start..

Ah okay I understand now thanks, yeah exactly me too I’m baffled I’ve always kept up with the oil etc and never drive the car hard when cold always make sure oil temp is fully warm etc.. okay thanks I will do, what’s the chances the engines toast or do you think it’ll be okay? Thank you

 

what oil did you use? I've seen some unexplainable engine wear from people claiming "I change my oil every 5000 km" which imo is completely ridiculous, but meanwhile they used 10W40 instead of 5W30, because they thought it was fine to use cheaper oil because they do change it more often.

 

10W40 is cheaper?

OP, you need to test oil pressure.

 

Have you checked out the AC compressor? The noise sounds outside, if you know what i mean.

 

Have you checked out the AC compressor?

No. I haven’t checked out that. How would I go about checking that out? And yes, I know what you mean, thank you for your advice.

 

Run with the belts off for a few seconds just to make sure it’s not belt related.

Your rod knock (if it is that) started before you got the car, no matter how nicely you drove and took care of it once it starts it will just get worse. I assume either last owner drove it very hard or starved it of oil somehow.

 

Run with the belts off for a few seconds just to make sure it’s not belt related.

Your rod knock (if it is rhat) started before you got the car, no matter how nicely you drove and took care of it once it starts it’ll get worse.

I assume either last owner drove it very hard or starved it of oil somehow.

Okay thank you I appreciate it, I’ll take the belt off in the morning and report back what happens, how long can it run with the belt off? Yeah I agree that seems to be the case.

 

It would have gone bang by now if it was internal,thats been my experience.

 

That’s my thoughts exactly I would’ve thought it would’ve blown up by now

 

Definetely do this first. If you haven't pulled off the fan and examined belts at this point it's time anyway. Make sure that tensioners and water pump pulley are properly fastened. I've seen a water pump pulley making an odd noise when it was fastened with only two bolts and one of those rather loosely. (not my work)

 

Yeah thank you I’ll pull off the belt and fan and give everything a check and listen, and oh really I’ll have to give them bolts a check make sure they’re all okay, thank you.

 

Perhaps vanos chain?

 

That’s a possibility the sound does sound like it’s coming from there it does sound like it’s coming from the top of the engine and towards the front but not all the way sounds like it’s right above where the chain and Vanos that’s from the ear I’m going to have a better look today and will post back

 

engine: “Knock knock knock…!!!”
OP: “Who’s there?”
engine: “Rod”

 

A mere shell of his former self.

 

Make sure the spark plugs are tight.

 

Thank you I have they’re all good all tight

 

If the main bearings were that bad i would expect the oil pressure warning light to come on a lot particularly when the oil is hot and thin.

 

Yeah that’s true I get you, oil pressure light has never came on during my ownership

 

Oil analysis, borescope, mechanics stethoscope. You gotta isolate the noise and use deductive reasoning. We can sit and guess till the cows come home, in the end you're the one who has physical access to the vehicle. Good luck!!

 

that won't cause a bearing failure in 77k, if ever.

Now, using coolant instead of motor oil, THAT might...

I agree- you're not going to have rod knock for 10k miles.
The rod will make a bid for freedom before that.

+1 for oil pressure check.
and a mechanic's stethoscope.

t

Thank you both for the advice I appreciate it, I have just been to my mechanic and he has said it sounds like the piston is hitting the top of the cylinder due to rod bearing and crankshaft gone bad he said it sounds like cylinder 2 looks like engine swap it’s going to have to be

 

but meanwhile they used 10W40 instead of 5W30,

that won't cause a bearing failure in 77k, if ever.

Now, using coolant instead of motor oil, THAT might...

I agree- you're not going to have rod knock for 10k miles.
The rod will make a bid for freedom before that.

+1 for oil pressure check.
and a mechanic's stethoscope.

t

 

Where in the UK are you? I am in Hastings and happy to have a look.

 

Hello mate, I’m from near bury st edmunds in Suffolk, that’s really nice of you thank you for your offer

 

Ac belt too. 15 - 30 seconds is all you need. It's gone or not.

 

Take all the belts off.

Okie dokie thank you I’ll take the belts off in a minute and report back

 

Take all the belts off.

 

If the piston's hitting, the borescope will show that very clearly.

That might explain the noise getting worse...
...as your mechanic had the car in front of him, and
we just have screens.

t
the internet causes more problems than it solves.

 

If the piston's hitting, the borescope will show that very clearly.

That might explain the noise getting worse...
...as your mechanic had the car in front of him, and
we just have screens.

t
the internet causes more problems than it solves.

yeah a borescope is a good idea thank you, would it hold compression good if it had been hitting, as I’ve done a compression test and it’s really good on all cylinders

 

Open the valve cover and look carefully at the cam timing wheels (which give signal to the cam sensors). They can hit other part of the bolts are loose. Look for shiny metal bits and rotating components.

 

No rod knock at all!!!! Now I think something else caused the noise and not rod bearings.

Oh really so you don’t think it’s rod bearing then? Did the second video not sound like rod knock or something, thank you for your advice I appreciate it I will do that in the morning, the sound definitely sounds above that region what bolts would be loose is it the ones on the timing wheels. When I first got the car I did have to install new camshaft position sensors as was driving it and it was extremely sluggish and I plugged my code reader in and got the codes for them, changed the sensors and it came back to life, could that have caused any problems in that region also? To add I had my valve cover off a week ago and camshaft looked in really good condition no scratches etc on the left one I didn’t look at the one on the right. Thanks

 

In the latest video, I can hear some knocking when it revs up, but it seems higher up motor than rods.

 

Thanks for watching the latest video, Yes the knock is high up in the engine if you place your hand on the top towards the front you can feel it and hear it the most

 

I heard the exact same rattle and it sounds like rod knock. You didn't rev it up higher like you did in the original video you posted with the belts on. Also, no indication of whether either video was a cold or warm engine. A warm engine will produce the rod knock more easily on startup, etc. I'm thinking your belt-free startup was a cold engine? If yes, all is still consistent with rod knock to my ear. Oil analysis will confirm metal in the oil (unless you recently changed the oil).

You hear it high up because this knock is NOT a main bearing at the crank at the connecting rod's bottom end. It's at the top end of the connecting rod where it connects to the piston's wrist pin and it happens at the top of the stroke where the piston changes directions due to the bang of the ignition of fuel which slams the loose piston down onto the connecting rod. A way to confirm without disassembly is to use a dial caliper. You take the spark plug out of the suspect cylinder. Set the piston so it's gotten to TDC and is just starting to descend. So if there is slack, and you put a wooden dowel down into the cylinder and pushed the piston down, you'd move the piston slightly and reveal too much clearance. Normally you can't get any movement. So, the dial indicator will show you the distance down to the piston BEFORE you push on the piston, and AFTER. It will show a slight movement. To confirm, it's wise to check another cylinder in the same way, or perhaps all the cylinders so you're good at doing the measurement and have a firm confidence that you've measured movement of one of the 6 pistons to confirm what I suspect. These tools are not expensive and some places may even rent you one, or perhaps a friend has one.

Make sense? Happy to re-explain and this will save you a ton of money if it proves NOT to show piston movement on the suspect cylinder. Happy to explain and even draw a diagram to help you find the right tool.

 

it happens at the top of the stroke where the piston changes directions due to the bang of the ignition of fuel which slams the loose piston down onto the connecting rod.

It can't knock at the top: Before the Bang by the spark, the rod pin is pushing the piston upward in compression, then BAng, the piston is pushing the rod pin down, and so the contact point never change and no knock. It will have light knock at before and after BDT as the pin pulls away from piston before BDT, then it pushes against the piston after BDT, so should be 2 knocks near BDT.