Hi chaps
I get lots of smoke on startup, which I am assuming is the valve seals as it quickly clears and runs ok on the move. Car is a '99 Xantia 2.0 16v auto Exclusive. I'm toying with attempting to change the valve seals with the head in situ - obviously I'll have to figure out some way of stopping the valves disappearing into the cylinders - is it feasible and has anyone tried it?
Also, I'm sure I've read somewhere that using thinner oil can cure it - the apparent reason being that it drains more easily back into the sump when you stop, so there's less to leak past the seals. Again, is anyone aware of this - has anyone tried it and does it work?
Smoke on startup
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CitroJim
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Ahhh, the stuff of legend 
Many claim it can be done in-situ but when pressed on precisely how, they all fall silent and run away
On the old Ford engines, indeed it was a very simple job. Cam out, compressed air or a coil of rope into the cylinder, valve spring off, new seal on and jobs a good 'un. Special tools were made especially for the job. What made it easy was the valve spring was totally exposed over its whole length.
The problem in the XU is the valve springs are heavily shrouded by the cam follower bores and there is little room available to compress them to get the collets off and even less to get at the seals. The seals are fixed very tightly onto their retaining spigots. My opinion is that it is a head off job and not one to be done in situ.
Before condemming the seals, check other possibilities. Do a dry compression test followed by a wet compression test (put a tablespoon of oil in each cylinder). If the wet readings are significantly higher than the dry figures, this indicates cylinder or bore wear as the oil helps the seal.
Check very carefully the crankcase breather system and give it a good and thorough clean. If the breater is blocked or the PCV valve is stuck open it can cause the problem. My 205GTi (which has no PCV) does puff off idle simply for this reason. Condensed oil collects in the breater pipes and then is sucked in the combustion chambers and burned.
Stem seals normally give themselves away by causing smoke under high vacuum conditions, for instance, when coasting downhill on a closed throttle and then opening up. Usually short puffs that quickly clear when back on power and the vacuum falls. Ring and bore wear normally causes prolonged smoke under heavy load.
Whatever, it needs fixing as the oil smoke will be doing your lambda sensor and cat no good.
Many claim it can be done in-situ but when pressed on precisely how, they all fall silent and run away On the old Ford engines, indeed it was a very simple job. Cam out, compressed air or a coil of rope into the cylinder, valve spring off, new seal on and jobs a good 'un. Special tools were made especially for the job. What made it easy was the valve spring was totally exposed over its whole length.
The problem in the XU is the valve springs are heavily shrouded by the cam follower bores and there is little room available to compress them to get the collets off and even less to get at the seals. The seals are fixed very tightly onto their retaining spigots. My opinion is that it is a head off job and not one to be done in situ.
Before condemming the seals, check other possibilities. Do a dry compression test followed by a wet compression test (put a tablespoon of oil in each cylinder). If the wet readings are significantly higher than the dry figures, this indicates cylinder or bore wear as the oil helps the seal.
Check very carefully the crankcase breather system and give it a good and thorough clean. If the breater is blocked or the PCV valve is stuck open it can cause the problem. My 205GTi (which has no PCV) does puff off idle simply for this reason. Condensed oil collects in the breater pipes and then is sucked in the combustion chambers and burned.
Stem seals normally give themselves away by causing smoke under high vacuum conditions, for instance, when coasting downhill on a closed throttle and then opening up. Usually short puffs that quickly clear when back on power and the vacuum falls. Ring and bore wear normally causes prolonged smoke under heavy load.
Whatever, it needs fixing as the oil smoke will be doing your lambda sensor and cat no good.
Jim
Runner, cyclist, time triallist, duathlete, Citroen AX fan and the CCC Citroenian 'From A to Z' Columnist...
Runner, cyclist, time triallist, duathlete, Citroen AX fan and the CCC Citroenian 'From A to Z' Columnist...
I forgot to make that distinction in my post. 
Thanks for the quick replies guys.
Hadn't thought about the breather system - it's often the simple things you forget to check - I've had a quick scan this morning and there are definitely signs of oil in the induction system around the throttle housing, so I'll take the breather lines apart first and give them a good clean. If oil is finding it's way into the throttle housing it's no wonder I've got smoke on startup!
Never looked at a PCV valve before, is it easy to check if it's stuck open?
I'll let you know how I progress. If it comes to it I'll take Jim's advice and take the head off to do the seals - sounds much easier!
Thanks again for the help
Hadn't thought about the breather system - it's often the simple things you forget to check - I've had a quick scan this morning and there are definitely signs of oil in the induction system around the throttle housing, so I'll take the breather lines apart first and give them a good clean. If oil is finding it's way into the throttle housing it's no wonder I've got smoke on startup!
Never looked at a PCV valve before, is it easy to check if it's stuck open?
I'll let you know how I progress. If it comes to it I'll take Jim's advice and take the head off to do the seals - sounds much easier!
Thanks again for the help