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1

Omega General Help / Re: Burning oil...

« on: 13 January 2026, 14:18:54 »

Update: So, after I took the damaged piston to an engine specialist I was told it was fine, clean it up and stick it back in! I did this, honed all the cylinders and a new set of rings in each. Compression readings all looked good. The engine has been running fine since, and I was hoping that the continued oil burning was just the new rings bedding in. However, 8000 miles later and it's still smoking and burning oil!!!

2

Omega General Help / x25xe Piston...

« on: 17 January 2025, 19:47:14 »

Does anyone have a spare v6 piston (and willing to post) please?

3

Omega General Help / Re: Burning oil...

« on: 16 January 2025, 19:13:53 »

You might get away with dropping the sump seeing as it's in a Vectra, but the piston has to come out of the top.

Could you do it? Probably.

Should you? No.

And what if you don't find anything? Do you strip the rest of the block? At that point why only do one. And do you then replace the crank bearings? Upgrade everything?

And if you're going to totally rebuild the engine you would be insane to try to do it in the car... On the kitchen table or living room floor would be questionable at best.

Ah, but if I don't do it I'll never know if it was caused by a chunk of ring or something else! Shouldn't take longer than 30 mins, and my garage is strewn with engine parts now anyway :-) By the way, I put new big end shells in when I did the top end, curiosity got the better of me and I wanted to see how clean,or dirty, it all was inside. I didn't touch the mains, as obviously that entails a much bigger step.

4

Omega General Help / Re: Burning oil...

« on: 15 January 2025, 20:53:05 »

Got the first head off and discovered damage. Markings in the head surface, marked bore and tiny nibble out of the piston. I'm guessing maybe a piece of ring broke off?

More likely to have been something that fell in before/as you refitted the heads. Not that it matters, because now you have an engine that's not worth reassembling as it, and almost certainly isn't worth repairing.

Can't think how, I was super carefull! Do you not think it could be a piston ring breaking up?  The scoring isn't deep, wondering if it's worth sticking in a new piston and rings as I'm thinking this could probably be done from underneath after dropping the sump, or does the crank have to come out on these?

5

Omega General Help / Re: Burning oil...

« on: 15 January 2025, 18:24:31 »

Got the first head off and discovered damage. Markings in the head surface, marked bore and tiny nibble out of the piston. I'm guessing maybe a piece of ring broke off?

6

Omega General Help / Re: Burning oil...

« on: 14 January 2025, 19:22:21 »

It does sound like one of the stem seals hasn't sealed.  Crankcase fumes would not produce that amount of exhaust smoke.

I'm so hoping so! Started stripping the engine so will soon find out...

7

Omega General Help / Re: Burning oil...

« on: 12 January 2025, 21:14:57 »

If the breathers vent into the plenum then they will put oil into the intake. Ironically, the cleaner the breathers are, the more crankcase fumes they allow into the intake.

So unless it's consuming enough oil to blow smoke rings, I would leave well alone.

I don't like the smoke, every time I leave a set of lights or roundabout. I also hate the smell, which is most evident sitting in slow moving traffic. It never did this in the 10 years before I did the top end work, so it has to be down to something I did wrong, or defective seals perhaps....

8

Omega General Help / Re: Burning oil...

« on: 12 January 2025, 17:45:01 »

Quick question before you blow it all apart...

Have you removed and cleaned the intake pipe between the air filter housing and the front variable intake valve?

It's not unusual for oil from the breathers to drain to the bottom as the crank case fumes cool and condense. (These fumes are what produces the oil that you see in the throttle body). Over time you end up with a fair sized puddle at the bottom of the y pipe. A decent full throttle pull width start to draw this oil into the intake and consequently the valves.

The plenums are a slightly different set up as this is in a Vectra, not Omega. When I redid the top end everything including breather pipes were all cleaned, although weren't too bad anyway. Also, before my rebuild, it burnt no oil whatsoever.

9

Omega General Help / Re: Burning oil...

« on: 12 January 2025, 15:14:57 »

I think you've damaged at least some of the valve stem seals. That's quite easy, as they're small, and buried quite deep in the head.


How did you push them into place before fitting the valves?


The bad news is that to fix this properly, the head will need to come off again.

I bought a special tool to remove the old ones and place the new ones. It went very smoothly I remember, all seemed to push into place nicely. I'm guessing maybe they have popped up with the valve movement for some reason. Yes, I'm resigned to the fact it's all got to come apart again, so I've bought a new gasket set. I'm guessing I won't need to skim the heads again though....

10

Omega General Help / Re: Burning oil...

« on: 12 January 2025, 11:44:58 »

One "easy" option would be the crank case breather, unless you already havenīt clean up the breaher box behind the block and the valve above plenum?

https://www.omegaowners.com/forum/index.php?topic=90653.0

There are good instructions for cleaning it up by the way

Thanks, yes I did look at the breather box and it all looked really clean, no sign of blockage. Before I refurbed the top end there was no oil burning at all, in fact never needed a top up between changes. My suspicion is that stem seals have popped off, or damaged somehow. I've heard of stem seal retainers, but can't find anything to fit this engine...

11

Omega General Help / Burning oil...

« on: 12 January 2025, 10:05:12 »

Hi all, any engine experts here?
Last year I rebuilt the top end of my X25XE but within a short time it was burning oil. This happened mainly after a period at idle, at traffic lights for example, blue smoke and that telltale smell.
All seems to point at stem seals, but I had replaced all these! What could've gone wrong? 
I've just started stripping the engine again, and with the inlet manifold off I can see what looks like traces of oil sitting on top of some of the inlet valves. Is this normal, or should they be perfectly dry? All the plugs look black, and some slightly oily, but prior to stripdown I ran the engine at idle for 15 minutes.
Any help/suggestions greatly appreciated :-)

12

General Discussion Area / Re: V6 Cam locking kit to buy/hire wanted..

« on: 29 August 2015, 10:29:51 »

Thanks henry, I'll give them a call. 

My belt hasn't been changed since 2008, but only done 40.000 miles in that time. I can hear a slight noise developing, maybe just water pump, but don't want to risk any more mileage in case it's the rollers/tensioner starting to give up :-)

13

General Discussion Area / Re: V6 Cam locking kit to buy/hire wanted..

« on: 28 August 2015, 19:56:20 »

Thanks for your replies... I'm in Cornwall, so a long way from you guys. I'll be up your way next month Jimbo, but need to get the belt done asap. I'm starting to hear an unfamiliar noise and fear it may be a roller about to give up 

14

General Discussion Area / V6 Cam locking kit to buy/hire wanted..

« on: 25 August 2015, 19:44:13 »

Time to replace the belt kit on my 2.5 Vectra B, does anyone have a locking kit to sell or hire please?

15

Omega General Help / Re: Best tyre advice? With emphasis on wet grip pleeeease...........

« on: 25 August 2015, 19:42:37 »

I put Uniroyal Rainsports on the front of my Vectra. Really impressed with wet grip, not on long enough to comment on longevity though...