Need your thoughts on this rattling noise and the strange reason why it has subsided

[[email protected]]

So I have had this really annoying rattle at tip in (when you first ease in the throttle) at 2200-2400rpm in all gears.

I thought it might have been the CCT chain kissing the AGN valve cover I have installed instead of the OEM one.

So today I checked the oil and it was low so I poured in 1/2 a liter of Castrol 5x30 synthetic. Initially I had the engine running, made a small mess, then shut the car off and completed the top up.

I start the car and rev the engine and the rattle is now at 5% of the volume level it used to be at.

So what the hell could the sound be from?

TIA for any thoughts/ideas as we are lost here trying to determine the source of the sound.

[J-jizzle]

Did you take the valve cover off to see if it was the chain kissing the valve cover?

[[email protected]]

We did a while back when we first heard the noise and there was no obvious points of contact or metal shavings anywhere.

It hasn't been taken off since.

[J-jizzle]

Hmm.. The only 2 cents I can add from my experiences would be an exhaust rattle. On my old car and my buddy's Jeep they would have rattle at a range of rpm for a short time like you described. Although your case being that it has become much more quite for some reason doesn't really make my idea plausible.

[[email protected]]

It wasn't an exhaust rattle that's for sure. With the hood up the rattle was coming right where the oil cap is and sounded like pulling a chain across some metal.

It is just weird that the sound subsided so much after adding some oil.

[dirtybrd]

Being .5 of a qt. low wouldn't affect anything.

[bavaria75]

Has mostly nothing to do with the oil.
My retainning pin or the little metal flag in the middle of the spring of the accessory belt tensioner, was making a noise bcause it was vibrating within the spring holder. just on cetain days and barely to hear. Only in the garage or in front of the car. Might help.

[[email protected]]

The thought that the oil must of lubricated some part just seems a bit reaching on my part.

Putting the oil cap on backwards shouldn't have done anything either.

What could rattle near the CCT?

[diagnosticator]

The thought that the oil must of lubricated some part just seems a bit reaching on my part.

Putting the oil cap on backwards shouldn't have done anything either.

What could rattle near the CCT?

Are you running the variable timing unit, the fixed timing unit from a non VVT engine, or the VVT unit unplugged? Has the cam drive chain been replaced? Is the cam chain tight with no free chain slack/slop between sprockets, confirmed? Consider reinstalling the stock valve cover temporarily for a test, see if the noise is still present with the stock cover in place.

[[email protected]]

I am running a new non-VVT unit with the VVT solenoid from the old unit plugged into to keep a CEL from showing. The new file I am getting will delete the code so I can remove the solenoid.

The OEM cam drive chain was reused. The chain was checked when the VVT unit was installed and rechecked when the non-VVT was installed.

My n00b thought is that if there was slack wouldn't the chain have jumped a sprocket by now and thrown the timing off?

[diagnosticator]

I am running a new non-VVT unit with the VVT solenoid from the old unit plugged into to keep a CEL from showing. The new file I am getting will delete the code so I can remove the solenoid.

The OEM cam drive chain was reused. The chain was checked when the VVT unit was installed and rechecked when the non-VVT was installed.

My n00b thought is that if there was slack wouldn't the chain have jumped a sprocket by now and thrown the timing off?

I suspect the chain is loose. When there is free slack in the chain, the slop will make a lot of noise at certain engine speeds, provoked by the torsional vibration in the cam shaft drive, especially when the torsional vibration frequency coincides with the natural frequency that the chain tends to whip at, depending on the amount of free slack in the chain.
You said the chain was checked when the fixed adjuster was installed. By what criteria was the chain evaluated? IE, was the chain almost drum tight all around between sprockets, or was there some slack evident? If there was some chain slack present, where was it at in relation to the sprockets, and how much?
The chain drive will run with a LOT of free slack and make terrible noises, for a long time before it get bad enough to jump sprocket teeth. In fact it is likely the chain would break from the stresses of whipping about, long before it was able to jump sprocket teeth.

[diagnosticator]

It wasn't an exhaust rattle that's for sure. With the hood up the rattle was coming right where the oil cap is and sounded like pulling a chain across some metal.

It is just weird that the sound subsided so much after adding some oil.

Is the oil fill port in the valve cover you are using, near the chain adjuster at the back of the head?, If it is, then soaking the chain with oil by adding oil, will temporarily reduce the tendancy of the chain slack to whip freely from the viscous friction drag of the oil on the chain.

[[email protected]]

I suspected it might have been a loose chain as well but the car runs great... it just rattled.

The oil fill point is near the back of the head where the CCT is.

I'd assume that if I let the car sit for a day and then drive it the oil would have drained back down to the pan and the rattle would come back but it didn't.

I'll monitor the noise for now and if it still remains but at such a low levell I'll consider swapping out the chain the next time the valve cover comes off.

So I guess I have to replace it with a chain from a non-VVT unit right? So a B5 cam chain should work?

[diagnosticator]

I suspected it might have been a loose chain as well but the car runs great... it just rattled.

The oil fill point is near the back of the head where the CCT is.

I'd assume that if I let the car sit for a day and then drive it the oil would have drained back down to the pan and the rattle would come back but it didn't.

I'll monitor the noise for now and if it still remains but at such a low levell I'll consider swapping out the chain the next time the valve cover comes off.

So I guess I have to replace it with a chain from a non-VVT unit right? So a B5 cam chain should work?

I think that the chain PN that is specified for the fixed timing, or non VVT chain guide/adjuster should be used with the fixed, non VVT CCT you are running with. The drive chain used with the VVT CCT, may be specific to the method employed, shifting the chain slack between the upper and lower spans between cam sprockets to change the angular position of the driven intake cam sprocket relative to the exhaust cam driver sprocket. The geometry of the VVT chain guides and the adjuster assembly accommodating the "extra" chain slack the VVT CCT manipulates to effect the intake cam timing.

The fixed or non VVT CCT, would therefore have less running slack built into the cam drive chain by design, because there is no VVT action, so the extra chain slack the VVT CCT must have to provide the VVT adjustment function, is not needed in the non VVT, fixed CCT drive chain.
The non VVT CCT drive chain would run tighter, with less chain slack compared to the VVT drive chain.

[dirtybrd]

The way the VVT works, the chain shouldn't have to be a different length. All the VVT tens. does is move both guides one direction. So they both move down together as well a up, retarding or advancing the chain.

[[email protected]]

We looked at the part numbers of the chain for the B6 and B5(non-VVT) and it is the same part number.

[diagnosticator]

We looked at the part numbers of the chain for the B6 and B5(non-VVT) and it is the same part number.

Actually I'm not surprised they are the same PN. Is there any free slack evident between sprockets with the chain installed now? If there is, then a new chain should be considered.

[lookaught]

Chains definitely need to be REALLY loose for them to skip... I've seen some horrifically loose and floppy chains in motorcycles and they dont skip... but I have seen one break. Damn near killed the rider when it broke, and left a foot long mark of every link in the aluminum swingarm. This was on an Aprilia RS250 racebike. He was very lucky that it just flew off and didnt bind and bunch around the counter shaft, which would have undoubtedly ruined the trans/motor.

[diagnosticator]

Chains definitely need to be REALLY loose for them to skip... I've seen some horrifically loose and floppy chains in motorcycles and they dont skip... but I have seen one break. Damn near killed the rider when it broke, and left a foot long mark of every link in the aluminum swingarm. This was on an Aprilia RS250 racebike. He was very lucky that it just flew off and didnt bind and bunch around the counter shaft, which would have undoubtedly ruined the trans/motor.

Yes, that is true, but the situation is regarding unusual noise possibley due to the chain rubbing on the valve cover or some other part. The symptoms don't involve the chain jumping sprocket teeth in this case.

[[email protected]]

Well this rattling noise issue pretty weird indeed.

My boys tell me the engine is still breaking in since I didn't get to drive it much after I got it back together. I didn't think a noise like that could be due to an engine still breaking in.

When I checked the oil level it was low again so I put in some 10w30 dino oil and the noise subsided a bit but it was still there. My oil pressure level was higher due to the thicker oil but I didn't think much about it as the car drove fine.

I did a 3000 mile roadtrip and on the way back home the rattling noise reduced in volume about 90% but the tiny rattle at tip in was still there. During the trip I noticed oil still being lost so I was routinely checking the oil level and topping it up with 10w30. I did notice that when I am on boost that was when I was losing oil. I was also losing coolant to a leaking coolant flange at the back of the head.

At one fuel stop I took my flashlight out and noticed that there was oil pooling up where the dipstick area was. I also noticed oil being blown to the top of the dipstick and collecting where the ribs at the top are.

I get home and had the boys check the car out for oil leaks and replace the rear coolant flange. They looked for an oil leak and found oil was being forced out from the bottom of the dipstick and a couple of other areas near my oil pressure sender. Looks like there is just too much oil pressure being generated and oil was escaping where it could.

They did a leakdown test and found only a 5% loss when the engine was cold so the rings were fine so no massive blowby was happening. Checked the catch can and it wasn't full of oil.

So I had an oil change done and got rid of the 10w30 dino oil and replaced it with synthetic 5w40 now that the engine has 'broken in'. Started the car and it purred like a kitten.

The rattling noise I had is all but gone and the lifter tick that was gone before is now back. Trade one noise for another I guess.

So the rattling and oil loss was due to the thicker oil I was running and the higher oil pressures that were being generated as strange as it seems to me. If someone can explain why this might have happened I'm all ears.