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[Derek_in_Penzance]

OK, different car, but it looks like V6 Omegas make a habit of this.

2.5 Elite estate, S-reg, 142k miles, running lumpy and lacking power. No water in oil. Compression test shows 225 psi on all cylinders RH side, 225 on LH front, 160 & 140 on the two rear LH pots.

Plugholes on RH side had a bit of oil in them, those on LH side dry as a bone. I was hoping that maybe it was just misfires due to oil, but obviously not.

So this is not dissimilar to my R-reg 3.0 Elite estate + LPG, albeit not quite as bad.

I'm not really asking for any help, just passing comment really, in the hope that someone might say "Yes, they all do that!". Then at least I might know what to do -scrap it most likely!

[Andy B]

  Bu66er!  

[Marks DTM Calib]

OK, different car, but it looks like V6 Omegas make a habit of this.

2.5 Elite estate, S-reg, 142k miles, running lumpy and lacking power. No water in oil. Compression test shows 225 psi on all cylinders RH side, 225 on LH front, 160 & 140 on the two rear LH pots.

Plugholes on RH side had a bit of oil in them, those on LH side dry as a bone. I was hoping that maybe it was just misfires due to oil, but obviously not.

So this is not dissimilar to my R-reg 3.0 Elite estate + LPG, albeit not quite as bad.

I'm not really asking for any help, just passing comment really, in the hope that someone might say "Yes, they all do that!". Then at least I might know what to do -scrap it most likely!

They dont make a habit of it unless:

1) Its a cambelt failure

2) LPG running lean taking a piston out or burning a valve

Certainly not a common issue....question is, which of the above is the cause!

[Derek_in_Penzance]

On this car, the 2.5, it's not LPG running lean as it hasn't got it!

Oh well. I'm learning to love these V6s.  

[Bandit127]

I must have read 20k+ posts on this forum. Not once have I read about:
Worn rings
Worn bores/rebores
Holed pistons.

What's the crack? Some sort of coating on the bores? I refuse to believe it's modern oil. Blocked breathers are proof of serious oil abuse and we get loads of them...

I also struggle to believe that clobbered valves can hold 10 (ish) bar. Surely that would be a case of all or nothing, pressure wise?

[Kevin Wood]

A slightly bent valve, or one in a cracked guide or with a burnt seat area might not seal as well as it should, and there's a lot of air to escape from a cylinder in not much time before it reads zero on a compression test.

Bores and rings tend to last the life of the car these days. I've certainly opened engines that have done 100k plus and found the honing marks still intact throughout the whole of the bore surface.

Kevin

[Derek_in_Penzance]

What I find interesting is that both cars are green, both are Elite estates, both have low compressions on two adjacent cylinders, with the rest good, and on both cars the low cylinders are the two rear LH ones.
One is 3.0 (LPG) and the other 2.5.

I have a blue saloon 2.5 as my daily car which is running OK at the moment (fingers crossed).

Maybe this just affects green estates?  

I have a red 2.5 CD estate too, as of last night. It does run, rather rough, but I dare not lift the bonnet.....

  

[Kevin Wood]

Well, I'm glad mine's blue. 8-)

 

Kevin

[The Red Baron]

if this is any consolation to you, my GREEN 3.0l estate & my GREEN 2.5l cdx are fine, so i think the colour doesnt matter eh.

[JamesV6CDX]

It seems that, if a head gasket is going to fail, albeit rare, it's usually on the passenger bank, at the rear...

[Derek_in_Penzance]

It seems that, if a head gasket is going to fail, albeit rare, it's usually on the passenger bank, at the rear...

It seems that you are right!

I wonder if it is for the same reason that C30SE engines suffer head gasket failure at about 100,000 miles? The gasket degrades, lets water through where it shouldn't, and the rear of the head then suffers lack of cooling as the water flow has been short-circuited. On both  my cars the two affected cylinders are those furthest away from the water pump (I think).

Of course they are both green too, which doesn't help.

[Andy B]

It seems that, if a head gasket is going to fail, albeit rare, it's usually on the passenger bank, at the rear...

It seems that you are right!

I wonder if it is for the same reason that C30SE engines suffer head gasket failure at about 100,000 miles? The gasket degrades, lets water through where it shouldn't, and the rear of the head then suffers lack of cooling as the water flow has been short-circuited. On both  my cars the two affected cylinders are those furthest away from the water pump (I think).

Of course they are both green too, which doesn't help.

Mine went at 150 000 No 6 cylinder/piston head was beautifull & clean.

[Derek_in_Penzance]

It seems that, if a head gasket is going to fail, albeit rare, it's usually on the passenger bank, at the rear...

It seems that you are right!

I wonder if it is for the same reason that C30SE engines suffer head gasket failure at about 100,000 miles? The gasket degrades, lets water through where it shouldn't, and the rear of the head then suffers lack of cooling as the water flow has been short-circuited. On both  my cars the two affected cylinders are those furthest away from the water pump (I think).

Of course they are both green too, which doesn't help.

Mine went at 150 000 No 6 cylinder/piston head was beautifull & clean.

The 2.5 car is 125,000 miles, the 3.0 one 165,000. My blue 2.5 saloon is at 145,000 and still going strong (touches wood...).

[Andy B]

It seems that, if a head gasket is going to fail, albeit rare, it's usually on the passenger bank, at the rear...

It seems that you are right!

I wonder if it is for the same reason that C30SE engines suffer head gasket failure at about 100,000 miles? The gasket degrades, lets water through where it shouldn't, and the rear of the head then suffers lack of cooling as the water flow has been short-circuited. On both  my cars the two affected cylinders are those furthest away from the water pump (I think).

Of course they are both green too, which doesn't help.

Mine went at 150 000 No 6 cylinder/piston head was beautifull & clean.

The 2.5 car is 125,000 miles, the 3.0 one 165,000. My blue 2.5 saloon is at 145,000 and still going strong (touches wood...).

I'm saying nowt! My Omega recently passed 150 000miles .....