Help

I have a 4.4 LPG converted 2003 L322, the pressure in the water system is very high you can't even squeeze the top pipe after using it. I've had head gasket checked, compression checked and all ok, it never overheats but was misfiring bait so put new plugs in and this solved the misfiring, it's started doing it again today after about 6 weeks so I took plugs out and 2 were covered in oil so ordered some rocker cover gaskets which il fit tomorrow to hopefully cure the misfiring and loss off oil. It's been to 5 garages now and each one has had no idea apart from saying its knackered but I use it everyday and it never overheats. Had rad out and checked and its fine, has had new water pump fitted to but still over pressures, anybody have any ideas what could be at fault? Thanks in advance

If you mean the spark end of the plugs was covered in oil, rocker cover gaskets is not going to help.
I don't know the L322, but it just sounds like 2 cylinders not firing so it would help if you told us which cylinders.
There is always a fair amount of pressure in the hoses which will rise to some extent when the car is stopped after a run, if it doesn't overheat I would worry first about diagnosing the missfire. Ignition, injector or compression. A compression test would be my first step.
Saint.v8 is pretty knowlegable on these cars.

Does it misfire on LPG and petrol?

Datatek said:

If you mean the spark end of the plugs was covered in oil, rocker cover gaskets is not going to help.
I don't know the L322, but it just sounds like 2 cylinders not firing so it would help if you told us which cylinders.
There is always a fair amount of pressure in the hoses which will rise to some extent when the car is stopped after a run, if it doesn't overheat I would worry first about diagnosing the missfire. Ignition, injector or compression. A compression test would be my first step.
Saint.v8 is pretty knowledable on these cars.

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Coming from an esteemed, knowledgable and respected LZ'er such as yourself Keith, I am honored.

It is often said the BMW M62 4.4 converts to LPG very well due to hardened valve seats but eventually it will succumb to seat regression after many years. With a flashlube system installed, this wearing of the valve seats is slowed, but will catch up after a good number of years. This can lead to oil loss, but not necessarily show on a compression check!

So first off would be a few questions,

How long has it been on LPG?
Does it miss on both fuels (as Paul asked)?
Have you carried out a hydrocarbon test on the coolant (sniff test)?

Change the expansion tank cap, it is designed to keep it at a set pressure, if it is faulty it could be the issue if it doesn't overheat...many BMW's suffered similar issues.

The M62 is a good unit, pity about the VANOS system though, but the rest aint bad....

Thanks for the replays, the oil is in the top of the plugs when you take rocker covers off, misfiring on 1 and 4 cylinders, been LPG converted for 4 years, changed expansion cap but new 1 leaks as soon as its upto temp so put old one back on which doesn't leak

Had compression check and was all fine on all cylinders, also had sniff test and was all ok. Also had new coil packs fitted

Is oil in all plugs, just one side, or only in the misfiring cylinders?

My hose get firm, can be squeezed if you put enough pressure on.....rock solid is an issue but i have large hands....

Now heres the thing...did the new cap leak due to over pressure or manufacture fault...try another!

Tried another and it was over pressure

Plugs are just drivers side, thanks

Are getting gas into the cooling system from a dodgy vaporiser ? Certainly not unheard of and well worth checking. Try running on just petrol for a while - take out the LPG fuse to make sure the system is isolated.

Have you got the right cap there are 2 types of one for diesel and one for petrol!!