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[JamesV6CDX]

My 2002 Facory LPG 1.6 Astra is losing oil as many know. It's been like it for the last 10k miles and not got any worse.

Symptoms are some blue smoke if you rev it when it's first started in the morning, and, blue smoke after a period of idle, EG sat at lights.

There is NO, repeat NO smoke, under heavy accelleration, or on the over run.

I'd have really thought if it were a ring, it would do it all the time?

There appears evidence of oil on the valve stems / seats when you look through the inlet manifold ports - even though 10,000 miles ago I changed all the stem seals.

When I did this, I couldn't detect any excess movement in the valve guides, although I'm not an expert with cylinder head internals.

Also - the compression on each cylinder, when you do a test, is way more than it should be - about 18bar+!

Any further thoughts?

I have some genuine GM rings at home, full set - just wanted to gather one last set of thoughts, before I strip it all down again! 

[JamesV6CDX]

Oil loss is 1 litre / 200 miles....

[Dazzler]

If you hold it at about 2500-2800 rpm does it blue smoke??? If not then i would be reluctant to touch the rings and look more closely at the head. IMHO.

[JamesV6CDX]

If you hold it at about 2500-2800 rpm does it blue smoke??? If not then i would be reluctant to touch the rings and look more closely at the head. IMHO.

If you hold it at around a steady 3k or 4k there is absolutely no smoke visible - only after a period of idle.

Thing is - for the compression on all pots to be that high, would imply that unwanted oil is getting into every single cylinder?  :-/

[Dazzler]

But oil coming in only after long idle or night stop points at the head and not the rings.

[JamesV6CDX]

But oil coming in only after long idle or night stop points at the head and not the rings.

I agree - it's just odd that after removing the head and changing all the seals, it's still doing it.

What else could be wrong with the head, to cause this? Cracked head?

[Dazzler]

Did you have the head crack and pressure tested??

Is it the same now as it was before you did the head job??

[JamesV6CDX]

Did you have the head crack and pressure tested??

Is it the same now as it was before you did the head job??

Yep, after a head rebuild and new HG, it's no better at all.

Shamefully no, I didn't have the head tested - because after looking at it, I was so convinced it was the stem seals (especially as the original ones were the crappy troublesome red ones...)

[Dazzler]

Did you have the head crack and pressure tested??

Is it the same now as it was before you did the head job??

Yep, after a head rebuild and new HG, it's no better at all.

Shamefully no, I didn't have the head tested - because after looking at it, I was so convinced it was the stem seals (especially as the original ones were the crappy troublesome red ones...)

Mmmmmmm Vx alloy head not being tested :-?.
Not something i would do.

Wait and see if any other ideas come along James, but i would rip its head off again and have it tested.
IF all is well then your half there to doing the rings

[JamesV6CDX]

Mmmmmmm Vx alloy head not being tested :-?.
Not something i would do.

I've never seen one fail before, and have changed a fair few... 

[Dazzler]

Mmmmmmm Vx alloy head not being tested :-?.
Not something i would do.

I've never seen one fail before, and have changed a fair few... 

Ive had a few needing skimming due to warping and only about 3 that were cracked.

MarkDTM will probably be the man for this one maybe.
Its ony my view your getting at the moment James.

[JamesV6CDX]

Your thoughts are appreciated mate 

[iainb]

James,
My mig is doing something very simular.     burning oil when stuck in traffic or left to idle for long period's.
But it passed the MOT less than a month ago with a clean bill of health
whats of intrests is I asked them to check for oil burning at idle and was told that it wasnt ?
My oil consumption is about 1L per 1000 miles but I can see the smoke when I pull away in traffic.
I am tempted to do a flush using diesel fuel, only about a litre when the warning of low oil comes on the screen and see if the deglaze fixes the problem.
I will let you know my result.

[Dazzler]

Your thoughts are appreciated mate 

Always a pleasure

[Gaffers]

Had similar symptoms on a veccy 4 pot.  Turned out to a valve stem oil seal with a hole in it.  Compression test will confirm piston rings if it doesnt then its head off I'm afraid 

[Dazzler]

Had similar symptoms on a veccy 4 pot.  Turned out to a valve stem oil seal with a hole in it.  Compression test will confirm piston rings if it doesnt then its head off I'm afraid 

James has stated that compressions are high

[feeutfo]

seems strange all 4 pots have the same too high compression reading? Surely if 1 or 2 seals where leaking it wouldnt affect all 4 pots?
If it was ring related 'would you have varying comp. readings? They wouldnt ware all at the same rate, would they?
Likewise, a cracked head affecting all 4 pots?

Just trying to think what would feed all four pots a very similar amount of oil? If i understand it correctly all 4 pots are over reading to 18 bar(that figure means nothing to me, but you say thats too much and all exactly the same near as dam it?)

Or am i missing something?

[Kevin Wood]

Is the crankcase beather system clear? Just wondering if the crankcase is pressurising?

Kevin

[feeutfo]

its like its over filled or something. although i'm sure its not,  is it worth an oil pressure test possibly?  :-/ or run the breather pipe to a seperate container as an experiment?? if it has a breather pipe set up?

[JamesV6CDX]

Is the crankcase beather system clear? Just wondering if the crankcase is pressurising?

Kevin

Squeaky clear, Kev

I've had it all apart and you could probably see your face in it.

[Vamps]

I would still be looking at valve seals, a massive problem with Vauxhall in the 80's +....

[JamesV6CDX]

I would still be looking at valve seals, a massive problem with Vauxhall in the 80's +....

But I've changed them all for genuine items 

[GArlington]

...
If i understand it correctly all 4 pots are over reading to 18 bar

I would check the 18 bar figure, unless you managed to install a supercharger it is HIGHLY unlikely. Normal compression is around 10-14 bar (AFAIR).

http://en.wikipedia.org/wiki/Compression_ratio

[feeutfo]

...
If i understand it correctly all 4 pots are over reading to 18 bar

I would check the 18 bar figure, unless you managed to install a supercharger it is HIGHLY unlikely. Normal compression is around 10-14 bar (AFAIR).

http://en.wikipedia.org/wiki/Compression_ratio

not familiar with the correct figures, and havent read all of your link, but an over high reading would seem feasiblle given the excesive amount of oil in the bore???..... or not? :-/

[markfree]

Why not try a can of this :-

http://www.omegaowners.com/forum/YaBB.pl?num=1254911978

Cheaper than a head off job

[GArlington]

...
If i understand it correctly all 4 pots are over reading to 18 bar

I would check the 18 bar figure, unless you managed to install a supercharger it is HIGHLY unlikely. Normal compression is around 10-14 bar (AFAIR).

http://en.wikipedia.org/wiki/Compression_ratio

not familiar with the correct figures, and havent read all of your link, but an over high reading would seem feasiblle given the excesive amount of oil in the bore???..... or not? :-/
 

Just my own maths and thoughts on that:
1) 4 pot 2 Litre engine makes it 500ml per cylinder
2) at 14 bar that leaves cylinder capacity at 35ml at full compression
3) at 18 bar the above is 28ml
4) that leaves difference of 7ml per cylinder = 28ml for all 4 pots

I expect (nearly) all oil present in the cylinder to burn on every stroke, I do not know if this assumption is correct, but if it is - after 600 revs (1 min of idling) the engine would have burned 300x28ml=8.4 Litres of oil

As I mentioned before the above calculations are based on my (limited) knowledge and few assumptions, but it provides food for thought...

[Kevin Wood]

Just my own maths and thoughts on that:
1) 4 pot 2 Litre engine makes it 500ml per cylinder
2) at 14 bar that leaves cylinder capacity at 35ml at full compression
3) at 18 bar the above is 28ml
4) that leaves difference of 7ml per cylinder = 28ml for all 4 pots

I expect (nearly) all oil present in the cylinder to burn on every stroke, I do not know if this assumption is correct, but if it is - after 600 revs (1 min of idling) the engine would have burned 300x28ml=8.4 Litres of oil

As I mentioned before the above calculations are based on my (limited) knowledge and few assumptions, but it provides food for thought...

Don't forget that you will get a lot of adiabatic heating of the gases as they are compressed which will push the pressure up much higher than the theoretical figure you've calculated, which assumes the temperature remains the same.

One also has to wonder about the accuracy of the compression gauge. FWIW, The compression figures are even, which speaks volumes more than the absolute figure. IMHO

That tells me that the piston rings are basically sealing well, otherwise any wear would be uneven across the pots. I doubt oil in the bores made a difference, again, because there would unlikely be the same quantity in each bore.

It doesn't mean there isn't a duff oil control ring that is allowing the main rings to become overwhelmed with oil when up to running speed, which wouldn't show up when cranking.


Kevin

[GArlington]

Just my own maths and thoughts on that:
1) 4 pot 2 Litre engine makes it 500ml per cylinder
2) at 14 bar that leaves cylinder capacity at 35ml at full compression
3) at 18 bar the above is 28ml
4) that leaves difference of 7ml per cylinder = 28ml for all 4 pots

I expect (nearly) all oil present in the cylinder to burn on every stroke, I do not know if this assumption is correct, but if it is - after 600 revs (1 min of idling) the engine would have burned 300x28ml=8.4 Litres of oil

As I mentioned before the above calculations are based on my (limited) knowledge and few assumptions, but it provides food for thought...

Don't forget that you will get a lot of adiabatic heating of the gases as they are compressed which will push the pressure up much higher than the theoretical figure you've calculated, which assumes the temperature remains the same.
...
Kevin

I only test compression by disconnecting the spark plugs and cranking the engine, I may be wrong, but my impression was that the figure stated in all manufacturers specs was COLD compression.

[Kevin Wood]

I only test compression by disconnecting the spark plugs and cranking the engine, I may be wrong, but my impression was that the figure stated in all manufacturers specs was COLD compression.

Yes, but the gas heats up in the cylinder as the piston compresses it regardless of whether the engine's hot ofr cold, which causes it to expand. This increases its' pressure so you have to add this pressure increase to the pressure increase due to the compression of the engine.

Kevin

[JamesV6CDX]

I just wonder......

I have checked the main breather pipe is clear, and the smaller breathers that I can see - but I just wonder if this is still a breather issue.

Reason being, there's a big breather that goes from the cam cover, to the inlet, directly above the butterfly.

If oil was dropping from here, into the inlet, then it would explain why there is a bit in each pot?

I feel a test coming on....

[feeutfo]

I just wonder......

I have checked the main breather pipe is clear, and the smaller breathers that I can see - but I just wonder if this is still a breather issue.

Reason being, there's a big breather that goes from the cam cover, to the inlet, directly above the butterfly.

If oil was dropping from here, into the inlet, then it would explain why there is a bit in each pot?

I feel a test coming on....

Exactly my thinking but not sure of the pssibilitys and the set up, is it routed correctly, any filters missing, does it/should it have a carbon filter or something?

I would def run the breather pipes to a a seperate container, block the holes off and see if it impoves....?