Hi all, I hope someone can help!

1997 Discovery 300tdi 89000 miles.

Came off the motorway yesterday and stood at the lights the discovery started smoking.

Only a little at first but did get a lot worse.

Managed to get home and it had used a little oil, from full on the dipstick to around half way.

Checked all hoses and no blockages or breakages. Smokes at idle and under load.

Checked exhaust and oil residue in there that wasn't there before.

Cleaned the cyclone breather too and put back together and still smokes.

With the engine running could hear air coming from the cyclone breather so thought there must be excessive pressure and removed the oil filler cap to check.

When you remove the oil filler cap there is a lot of pressure escaping but the smoking stops.

Had to pick the BH up from the hospital so taped a bag over the oil filler gap hole to catch any oil and it ran fine with no smoke at all.

New head gasket around 8 months ago and no coolant loss whatsoever.

What would be the next thing to check?

Could it be valve oil seals or something more serious?

Thanks in advance!

Valve seals wont pressurise the crankcase, the reason it stops smoking when you take the filler cap off is that the excess pressure can escape easier. When it is on the crank pressure vents into the intake manifold via the cyclone, Could be a HGF or worn rings / bore. Worth checking the turbo is clean if its been breathing its own oil and also get the coolant sniff tested to see if it has been contaminated

Hi and thanks for your reply.

With hindsight I realised the only way to find the problem is to take the head off.

Engine stripped and headbolts out but the head stuck tight!

Signs if rust on some of the bolts so suspect HGF.

Job for tomorrow now, will report back when I know more.

Cheers

Back together and still the same problem.

With the cyclone to intake pipe still off there is no noticeable pressure coming from the pipe but the oil cap still pressurises.

Is the Cyclone at fault?

Check for play in your turbo. I'd say that's very suspect

Crank case pressure is from worn piston rings / bores, blown head gasket or cracked head, nothing to do with turbo.

You need to do a compression test.

For those who have the same issue.....

HGF caused hot pressure in crank case which fried cyclone!

New head gasket and new cyclone problem solved!

Turbo did kick a lot of oil through but fine after a can of turbo cleaner!

Weirdly though, the nut just before the oil filter worked lose (actual finger lose) and dumped about a pint of oil!

All sorted now!