grinding noise when revs drop

[JamesSap]

Hey guys,
My ecotec vt makes a sort of grinding noise after revving, as the revs come down right towards the end there is a grinding noise which lasts around 1-2 seconds, which is coming from the front of the engine. Sometimes on idle its barely noticeable, sometimes its not. It always happens when revved, doesn't matter if you barely move the throttle or go wide open. If revving harder though, the noise lasts longer, about 3-4 seconds rather than 1-2. All of the idler pulley bearings have been changed, new p/s pump, water pump, ac condenser and belt. possibly tensioner? was also thinking might be something more serious, like balance shaft bearing, maybe cam bearing? its definitely coming from the front of the motor. Any ideas would be much appreciated. Thanks guys

 

[Commo64]

Any video of the noise occurring?

 

[JamesSap]

Any video of the noise occurring?

Doesn’t look like I can post videos on this website, only photos

 

[JamesSap]

Any video of the noise occurring?

I have uploaded a YouTube short of the issue, here’s the link

 

[vxcalais_01]

Can you do a vid from the bottom ? Like from under radiator direction ? Does it sound like inside the engine or like sagging mounts and sump kitting the crossmember ? If not, can be water pump, timing chain, lifters, springs, bearings, harmonic balancer etc. I note you changed some of these already....does it sound like harmonic balancer ? Noise is usually constant with those. Can even be an exhaust leak...check your manifold bolts, etc. If its driving well otherwise probably more like an exhaust leak somewhere as the engine revs slow down the exhaust pressure drops. Do a few more vids.

 

[JamesSap]

Can you do a vid from the bottom ? Like from under radiator direction ? Does it sound like inside the engine or like sagging mounts and sump kitting the crossmember ? If not, can be water pump, timing chain, lifters, springs, bearings, harmonic balancer etc. I note you changed some of these already....does it sound like harmonic balancer ? Noise is usually constant with those. Can even be an exhaust leak...check your manifold bolts, etc. If its driving well otherwise probably more like an exhaust leak somewhere as the engine revs slow down the exhaust pressure drops. Do a few more vids.

The motor mounts are new, as well as the water pump, and all other accessories. I had the lifters out when I recently did LIM gaskets and gave them a clean. I doubt it’s harmonic balancer because when listening to the sound it’s definitely coming from the front mid-top area of the motor. I’m beginning to lean towards timing chain rattle, it sounds rather plausible and is ironically the one thing I didn’t check when doing the LIM gaskets. I will take some more video’s though just to be sure before I start pulling it apart again

 

[mirrabucca]

so... How did you get on?
A quick check of all the idlers, pulleys, belt, water pump, alternator, A/C compressor is to remove the drive belt and start it up.
Even if the sound persists, you will be surprised at how quiet the motor is.
My bet is timing chain, maybe cam or balance shaft bearings.
How many k's on it? Have you changed the oil with the specified grade?
I had lots of lifter noise on mine. I used ran an oil flush, then ran 5W 30 in it for a short run. Then changed the filter and refilled with the corect grade oil. Problem gone.
My car has 352,000 k's on it.

 

[JamesSap]

so... How did you get on?
A quick check of all the idlers, pulleys, belt, water pump, alternator, A/C compressor is to remove the drive belt and start it up.
Even if the sound persists, you will be surprised at how quiet the motor is.
My bet is timing chain, maybe cam or balance shaft bearings.
How many k's on it? Have you changed the oil with the specified grade?
I had lots of lifter noise on mine. I used ran an oil flush, then ran 5W 30 in it for a short run. Then changed the filter and refilled with the corect grade oil. Problem gone.
My car has 352,000 k's on it.

my car has 310,000ks and yes I have the correct oil in it. I haven't had the time to fix this issue yet, it doesn't seem to be getting worse so I'm just chipping away at little things with the interior before I undertake this fairly big job.

 

[vxcalais_01]

my car has 310,000ks and yes I have the correct oil in it. I haven't had the time to fix this issue yet, it doesn't seem to be getting worse so I'm just chipping away at little things with the interior before I undertake this fairly big job.

Timing chain is not something you would normally check when doing a LIM and they chains weren't common for going on these cars unless higher pressure lift was run on them. It's not so much the chain but the crappy tensioner and spring that holden chose to use. Decent poo job getting to it having to take off front cover. May as well do the balancer as this needs to be removed. Oil pump, water pump. Get a whole new front cover with gasket and seal. Decent price on the bay for em. When you doing all that you will wish you dropped a cam in afterwards. Cars are like a shredder for money and sore back and knuckles....let us know how you go.

 

[krusing]

On my L67 I had a Very similar noise while it was idling down,
And found it was the Air-conditioning Compressor, I turn Air Con off, and the vibration would disappear,
I have since replaced the compressor, and had no noise for some time, but it’s starting to re-appear,
I looked around and found one at “Central Motor Wreckers” in Ballarat that had it list to have done only 70,000 k/s,
I rang them and said I will buy that one, drove there from Melbourne and when I got there, I showed him the one on thier add, they told me they had just sold it,
ye right !, with an hour and a half.
The guy said we have another one similar,
So I opted to buy it, thinking it was legit,

I got screwed over from
“Central Motor Wreckers”,
when I got home, I cross referenced the tag on it to the vehicle in question via the VIN #
The one they sold me had done over 200,000 k’s,
I rang them and told them I deliberately drove from Melb to get a good compressor as you had advertised,
And guy at the end of the phone didn’t care give a fcuk, his answer was it’s the luck of the draw.

Side Note: the one they sold me wasn’t even cleaned, and have since notice it weeping air con oil.

Morel of the story,
“DONT buy from Central Motor Wreckers” as they also advertise on eNay