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[CplSkidmark]

Major request for help here. Having just bought a W plate 2.5 auto with a 2006 lpg conversion which was perfect (for 11 years old) I now find 400 miles later that it has either/or the problems in the subject line. The motorway journey from Cheshire to Fife did it in!
I would rather keep the car than sell it on (it IS that good) but as I have no technical knowledge or ability, or anywhere to use as a workshop, nor the right tools to carry out anything other than really basic fastening/unfastening, I hope somebody can direct me to a reliable and relatively inexpensive repair shop somewhere near Glenrothes, Fife. PLEASE!!

[tunnie]

what makes you think head gasket has gone, what symptoms do you have?

[CplSkidmark]

Thanks for the very quick reply - I took the car out to Wellside Motors as (apart from a loss of heat in the car) the main symptom is a misfire when on gas and as they're the local lpg conversion people they seemed a good place to start.
There is a repeating airlock which is released when the header tank cap is opened. There are air bubbles apparent when the engine is revved a little, also there seems to be at least one cylinder not firing correctly which is noticeable at tickover.
The problem is actually their diagnosis, I was hoping for something much easier. They didn't want to even talk about fixing it as they said it would cost more than the car is worth. There seems to be no loss of power in normal driving, there's no water visible in the oil, the coolant system does not seem to be pressurizing as much as I would expect (even though I am almost completely ignorant re mechanical things) as I have had 2 motors previously with head gasket problems!
Hope this info helps. Wellside did say they had converted one Omega previously and swore they would never do another one, so maybe they just don't like 'em?

[albitz]

It is possible that the plumbing of the LPG system into the coolant system has been bodged, which might cause airlock and heating problems etc. Air bubbling in the coolant does suggest HG though.
Cracked head - unlikely imo. :-/
The misfire on gas, is probably also related to the lpg system (may just need a new filter) if it was related to the engine itself the misfire would also be present on petrol.
Could also be a problem on the HT side of things. LPG needs the HT circuit to be in good condition to work effectively. Could just need a set of plugs. Have you checked your plug wells for oil?

[tunnie]

Omega is straight forward to LPG, space is at a bit of premium in the V6, just see our install guides.

Nothing there screams HG failure to me. How does it run on petrol?

[Kevin Wood]

Misfire on gas could well be the LPG system needing maintenance. How does it run on Petrol?

The expansion tank will pressurise, and release pressure when you open the lid. This is normal. In addition, if the engine is fully warmed up it may well bubble up as the pressure is released due to localised boiling inside the engine. The system relies on the pressure to keep the boiling point of the coolant high.

The heater not working, in addition to running problems on gas makes me suspect that the coolant circuit to the vapouriser is causing problems, perhaps airlocking and preventing the correct flow of coolant.

Suffice to say that head gasket failures are very rare on these engines and I'd be surprised if that was the problem.

It does sound like the garage you took it to were looking for excuses not to touch it.

Kevin

[CplSkidmark]

Thanks guys - this really is an active forum!
There is a slight unevenness on (petrol) tickover- again, Wellside reckoned this was due to one cylinder being poisoned by water ingress.  It seems to run perfectly on petrol, even the lpg eventually runs almost ok (very rough at tickover, mind)
Been in touch with the previous owner (who phoned me back as he was unavailable for my call) who says he doesn't understand why I've had the problem as he's been all over with the car since the heads were skimmed and gaskets, cambelt, water pump, oil pump etc replaced not that long ago. The car is sitting at 97,000 miles which I know is nothing for these motors. There is an acrid smell as it warms up, which never gets too bad and does vanish at normal operating temperatures. Doesn't smell particularly of exhaust, though. 

[tunnie]

What kind of LPG system is it, mixer or sequential?

First off, i'd do paperclip tests (details in maint section) read codes and post them up.

As others mentioned, LPG needs a stronger spark to ignite, so it could just be a old/damaged spark plug.

[CplSkidmark]

Re the smell - new tailpipe fitted the morning I got the car. It does smell a bit like "new exhaust"! Did I mention technical ignorance?

[CplSkidmark]

LPG is Zavoli multipoint, service carried out about 6,000 miles ago. Oil is clean. Servicing has been carried out by a mechanic friend of previous owner, as was head, cambelt etc., so no actual dates/mileages available.
Will check maintenance section for "paperclip test". Sounds fascinating...(just showing off my lack of knowledge, presently I have no idea what I'm about to find out)

[Kevin Wood]

Worth checking the spark plug wells for oil leakage?

That will cause a misfire as it breaks down the insulation on the HT leads. Any misfire will be worse on LPG, and if they used the cam cover gaskets that came in the gasket set when the HGs were done I'd put money on them starting to leak.

A bit of oil leaking onto the exhausts might explain the odd smells too.

Kevin

[CplSkidmark]

Thanks guys - will follow up all these tips/suggestions. Or get more technically capable/knowledgable friends to! Will let you all  know how I get on. Any further tips would be welcome. Thanks again.