Exhaust discoloured at high rpm

[xover]

What can be the cause of this?

Monaro ls2

[leigh1050]

How do mean" discoulored exhaust "?
Are the exhaust gases blue/black?
Have you got stainless headers that have blued?

[xover]

leigh1050 said:

How do mean" discoulored exhaust "?
Are the exhaust gases blue/black?
Have you got stainless headers that have blued?

Grey smoke.

[leigh1050]

Could be your burning a little oil.

[SturdyHSV]

If you've got the possibility to film it that might help diagnosis?

If it's black, then that would generally indicate it running rich. If it's bluey, then it's burning some oil.

Could check oil level to see if it's dropped appreciably? May take a fair few miles to really decide whether it's using any though.

[V8TFT]

Could be running slightly rich at high RPM. Normal from what I understand.

[xover]

I have an oil leak, but notice that the engine loses oil faster when revved so is that the piston rings? Is that an engine rebuild? $$?

[stevieturbo]

Perhaps state just how much oil it is using ?

[xover]

stevieturbo said:

Perhaps state just how much oil it is using ?

Probably get through a 4 litre bottle in six months, I do 4500miles per year max.

[Mud_]

That's a lot!

[stevieturbo]

More than a litre per 1000 is a lot.

But you'd really need to investigate where it is going.

ie it could be crankcase breather/PCV related, valve guides/seals, piston rings, external leakage etc etc

[xover]

stevieturbo said:

More than a litre per 1000 is a lot.

But you'd really need to investigate where it is going.

ie it could be crankcase breather/PCV related, valve guides/seals, piston rings, external leakage etc etc

Cheers for the info.

[SturdyHSV]

xover said:

stevieturbo said:

More than a litre per 1000 is a lot.

But you'd really need to investigate where it is going.

ie it could be crankcase breather/PCV related, valve guides/seals, piston rings, external leakage etc etc

Cheers for the info.

I may have missed it, but what sort of mileage has the car done? Don't quote me on any of these, but easy-ish things to check / look for:

Crankcase breather / PCV related.

Remove the throttle body (4 bolts and some jubilee clips to remove intake pipe). Is the inside of the intake manifold covered in oil? I think to be fair they all pull some oil through, so this may not really give you any extra insight... Could try putting a catch-can on, simple to install (couple of bits of hose) and see if that clears it up.

Valve guides/seals

Does it burp out some blueish smoke on starting up after sitting for a bit? This can indicate that oil that made its way up to the valvetrain while it was running then settled around the valve seals etc. when the engine was off. If it isn't sealed, it will leak through and thus be burnt when you start it up. This may not account for that much consumption though to be honest, but I'm not an expert. I believe if you see blue smoke under deceleration this can be a sign too, as the vacuum created when the throttle is closed pulls oil past the valve seals.

Piston rings

I believe this would let oil past and thus burn oil pretty much constantly, but I don't know whether initially it would only be at high loads etc. would need someone who actually knows what they're talking about to chip in here...

External leaks

I'd imagine you'd notice a litre of oil under your car, noticed any drips when parking up hot or anything?

[xover]

Thanks I will check this out.

No oil is hitting the ground.

The car has done 85,000miles. How long are the engines and gearboxes good for?

Edited by xover on Friday 12th May 11:45