PCV valve in Xantia TD

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JohnCKL
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PCV valve in Xantia TD

Post by JohnCKL »

Xantia 1.9TD does have a PCV valve which vents oil vapour from the engine oil sump to the air intake, doesn't it? I've read of complaints that the oil vapour dirties the air intake hoses and intercooler into the turbo, rendering them less effective. What is the function of the PCV valve and what happens if we block it to prevent the oil vapour going into the air intake? Perhaps some of you would have the solution and done something already?
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AndersDK
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Post by AndersDK »

John -
All engines have some means of venting the oil sump into the air intake. It's an environmental issue - and also to prevent the bypass combustion pressure building up pressure in the sump - making the oil-dipstick hole an oil geyser.
This may also happen if oil/water fume mix (mayonnaise) freeze during wintertime.
On ancient engine types a simple vent meshfilter was fitted to the sump - letting out fumes to open air.
It's important the fume hoses are lead into the air filter BEFORE the filter unit - to catch excess oil. Therefore it's also important to service the air filter at every oilchange - ensuring it's not clogged by oil.
Dave Burns
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Post by Dave Burns »

There isn't a pcv valve on these diesels, what you have is simply a crankcase breather pipe from the oil filler tube into the rubber air ducting after the air filter, if this were positioned before the air filter it would very soon foul the paper element and make the passage of incoming air very restricted.
PCV valves AFAIK are only to be found on petrols, PCV, positive crankcase ventilation is a system where the blowby gasses are positively extracted from the crankcase via the intake manifold.
Dave
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AndersDK
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Post by AndersDK »

Dave -
Is the Xantia 1.9TD different from the BX19RD in the air filter ?
On the BX19RD (n/a) diesels I've seen - the fume hoses allways goes into the filter box - BEFORE the filter element - which is known to clogg the filter with oil on service neglects.
JohnCKL
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Post by JohnCKL »

Thanks Dave, Anders. The Xantia 1.9TD fume hose goes in after the air filter box, so preventing the filter element from clogging with oil. However, in doing so, the excess oil goes to contaminate the intercooler, doesn't it? I searched the net and there seemed to be some aftermarket retrofit of crankcase vent filtration system either closed loop or open vent filter element. Has anybody fitted these kinds of filter systems and does it help, assuming that the intercooler is cleaned after installing the filter? I was wondering if the turbo itself will be contaminated with the oil? Anybody has ever taken out the turbo and clean it? Or it needs cleaning only by professionals? Does it need cleaning at all, after 7 years of use, mine is 96 model.
Dave Burns
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Post by Dave Burns »

Yes Anders as John says the breather enters the ducting well after the filter box, its also similar on the ZX TD.
The intercooler will eventually become oiled from the turbo its self, it would be unreasonable to expect any other given the speed and temperatures it has to endure, it has hydrodynamic bearings like the rest of the engine and as such recieves the same pressure of engine oil, up to some 70 psi at max. revs.
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Post by xantiaBFY »

guys,
I know I am bringing out an old issue here but apart from the environmental issue would it be detrimental to the engine if it is vented into the atmosphere direct.e.g. loss of power etc.
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JohnCKL
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Post by JohnCKL »

As far as I know, should not be detrimental to engine but instead benefits it. The blow-by gases are mainly engine oil vapour which will burn off in the engine anyway, giving the typical diesel black smoke. There will be some exhaust gases and fuel gases seeping past the piston rings. Since venting my CCV outside, got better starting, less black smoke on load and cooler engine (max 95C), all are positive benefits except for the environment. However, I need to overhaul my engine as the blow-by is high, needing to top up engine oil every 2-3 weeks.
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