G60 Pinking... a little more info please?

[Jim 2]

Similar problem to Mike Edwards here.. just that his post kinda inspired me to remeber something that Vince said at the last rolling road day.

 

I've been chasing this eternal rattling kinda noise that my car has under acceleration. I'm pretty certain its not heat shield or 'bit of metal knocking on other bit of metal' kinda problem because of three things :

 

a) It increases speed the more you dial round the revs

b) It seems to fade away once the car hits about 3,500RPM (G60 sweet spot!)

c) It doesn't do it when the car is stationary and you rev it

 

Vince suggested that it could be the car pinking, but I didn't see how that was possible at the time as I have pretty much run it on BP Ultimate or Optimax since buying it, and am running an SNS chip. But then I saw Mikes post about the knock sensor and if that gives up the ghost it can cause pinking.

 

The sound is very very noticable when the windows are down, not so much when they are up - it sounds almost like a ball bearing rattling around in the bottom of the engine / exhaust downpipe or centre section. I tried to get my car booked into Stealth for a checkup but the earliest Vince could fit me in was a month and a half ahead which is a bit of a wait :(

 

Anyone? The noise is driving me nuts. I love this car, but this noise is going to drive me insane slowly.

[24V Renshaw 0]

Jim,

 

I am pretty sure the noise is caused by a leak/crack in the downpipe, or downpipe gasket. I replaced my downpipe a while back and it stopped. It is not pinking, its a very different noise. The best way I can describe the noise is like a ball bearing rattling in a plastic cup. However since my front engine mount went it has started again, as it was a second hand downpipe and I reckon it has caused the same problem again. I am almost 100% certain that is what it is as I have replaced everything and as I say, when I replaced the downpipe it went away.

 

Let me know if you do it and it stops. I am planning on an engine swap but at least if I can get rid of the noise while I am getting everything sorted I will be happier.

 

Jay

[Jim 2]

Hm.. thanks for that Jay. I'll have to look into it.. I guess you share the same frustration as me because especially on a morning its a bloody god awful noise.. seems to improve very slightly as the car warms up which would back up what you say as the metal in the exhaust expands a bit and slightly seals the leak or crack you are talking about?

 

Wonder :

 

a) how much a new downpipe is

b) how much it'd cost to get one fitted

 

:?

[solomk1 0]

are you sure its not the crank shells as i am hearing this is a rather common problem on the g60 units !!!

[Jim 2]

If you mean what I have read about before as 'bottom end shells' I did wonder about the same kind of thing also.

 

Jay's suggestion about the downpipe does seem totally credible though so.. its a bit difficult to know whats to blame. Maybe Darren at G-Werks might be able to diagnose it whenever it is I manage to get down there for my rebuild :)

[h100vw 0]

The big ends are the ones that wear out on G60s. The knocking that creates, in my experience, can be heard best on a light throttle in first gear just about 1500 revs. The rest of the time you couldn't hear anything at all.

A cheap job if that is it. ten quid for the shells and a couple of hours to change them. If you are being really keen then you should replace the nuts and bolts in the rods too, which is about another 20.

 

gavin

[24V Renshaw 0]

I thought it was the big ends, so did them all drove down the road and there was the noise again. Big ends is a much deeper knocking, the one Jim and I are on about is like a ball bearing in a plastic cup.

The only time I got rid of it was when I put a different downpipe and manifold on, but it came back shortly after my front engine mount packed up.

 

Jay

[Jim 2]

Do you get the same other symptoms as me as well Jay? Like the increase in the speed of rattling as you go further round the revs, and the way it seems to fade out by about 3500RPM?

[Mike Edwards 0]

That would be what I have.

 

I have new mounts all round though and the front one is a bit serious.

[Jim 2]

I don't know about my front mount, but I think my rear mount is quite new and good quality.

 

But either way I need to look at getting this thing sorted cause it totally ruins the sound of the car imho - I don't think its as noticable to bystanders as one might imagine it to be when inside the car but it still sucks! :(

[Supercharged 2]

I have new mounts all round though and the front one is a bit serious.

 

I need a new front one asap - what have you got mike, Vibra-Technics??

[LowG 0]

Jim have you checked your plugs? Give em a good clean with a wire brush. They would give you rough idea if you are pinking that bad. Having an a/f gauge on g60 helps getting a rough idea on your mixiture which could reduce chances from any serious meltdown. For ultimate accuracy having a wideband readout would tell you exactly whats happening with your fuel mixiture.

 

rgds

[Jim 2]

Migs - the plugs are fine. They were only swapped for the W6 blah thingy plugs a few months back at a 20,000 mile service, and just had them all out the other day when running a compression test on my car. There was a little oil around the thread on each plug but the actual tips were clean and dry.

 

As a few have said, we think its not pinking, but related to a crack or leak on the main downpipe - seems there are already 3 of us in this thread with the exact same problem already.

[Mike Edwards 0]

The one on mine is a Volksport.

[24V Renshaw 0]

ITS THE DOWNPIPE OR MANIFOLD!!!!!!! :)

Seriously I have totally re-built my engine from the ground up, twice, its not pinking that Jim is on about its a different noise, that dissapears as the revs get higher and goes up exactly in relation to engine revs. It can be caused while a front engine mount is knackered and remains afterwards even with a "serious" one. Jim replace the exhuast manifold, the gasket, the studs, the downpipe and both gaskets and the front engine mount if it is knackered and I bet you it will go away.

 

Jay

[Jim 2]

Looks like I need to talk to Stealth then.

 

I do really want to get this sorted so.. any idea what kinda cost for parts and amount of labour involved are we are talking here Jay?

[24V Renshaw 0]

I don't know how much you would have to pay for new parts, but I know its a pain in the ar5e of a job to do. I actually replaced mine when I rebuilt the head so that made it easier to do.

 

Jay

[Jim 2]

Hm.

 

Probably file this one away for 'when I have oodles of spare cash' then - it certainly sounds expensive if its a PITA kinda job to do :)

[24V Renshaw 0]

Just shut the windows and you can't hear it! :D