Volvo S80 T6 2004 - Tight tappets & valve adjustment.

James02Marsh · Post by **James02Marsh** » 01 Nov 2019, 07:37

This vehicle has an LPG conversion. Recently on starting it has been misfiring (on most cylinders) first on petrol & the when it switches over, on gas. After a time it usually cures itself & runs OK but it appears to be getting worse.
I have been told that because it has the LPG conversion the valve & tappets have not been given enough 'lubrication' which they would normally get from petrol & that the tappets are tight & the valves need adjustment. I have been told the tappets are hydraulic & not adjustable - I'm not sure abou the valves.

Glad for any helpful comments on this please.

Thanks,

James.

Post by **SuperHerman** » 02 Nov 2019, 23:52

I think this is your part number for the lifters or tappets: 1298586

If I recall correctly these are not hydraulic or adjustable - they are "solid", but not solid as in one lump of metal. They are not adjustable.

The valves are also a fixed length, therefore not adjustable.

I have also heard that LPG is hard on the valve train - I don't fully understand it as the oil is coming from above and should be bathing everything nicely. Extra heat should be handled by the computer. My reading on the matter gives no perfect answer. LPG leaves a cleaner engine and engine oil, but like your experience I have heard of issues with valves.

Have you tried changing your oil to one designed for LPG?

James02Marsh · Post by **James02Marsh** » 03 Nov 2019, 02:34

Thanks, that seems to confirm what I have been told. I have recently put an additive into the oil & also the petrol. It now appears to run on petrol without problems. On LPG it is still missing, or variable. I didn't know that there was a specific oil for LPG, but I'm told that there is a 'lubricating' system which is sometimes put in alongside the LPG system when it's installed, which my vehicle does not have.
Any other comments are gratefully received. This has been a very reliable & easy vehicle up to now & I'd be sad to have to change it.

Thanks again,

James.

Post by **MoVolvos** » 04 Nov 2019, 21:14

James02Marsh wrote: ↑03 Nov 2019, 02:34 Thanks, that seems to confirm what I have been told. I have recently put an additive into the oil & also the petrol. It now appears to run on petrol without problems. On LPG it is still missing, or variable. I didn't know that there was a specific oil for LPG, but I'm told that there is a 'lubricating' system which is sometimes put in alongside the LPG system when it's installed, which my vehicle does not have.
Any other comments are gratefully received. This has been a very reliable & easy vehicle up to now & I'd be sad to have to change it.

Thanks again,

James.

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Post by **jimmy57** » 04 Nov 2019, 21:54

A 2004 Volvo engine uses solid tappets. The tappets are sized in increments are are changed to adjust valve clearance once a full measurement of all tappet to camshaft base lobe clearances is made. Gaseous fuel engines if factory built that way have hardened seats and valve faces to withstand greater wear that no fuel lubrication and no exhaust deposits will give the valve and seat contact area. If the LPG/CNG system is added by a converter later then the enhancements will not be in the engine for that service. The wear does decrease the clearance and can result in loss of valve sealing if the wear is great enough to eliminate the clearance.