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Turbo Underboost Causing Excessive Blow By?


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1st post so go easy!

Bought a mk2 1.8tdci with 133k on the clock. Engine was pristine when I bought it but 3k later the engine management light comes on.

Scanned it and get p0299 Turbo Under Boost. Had a fair amount of black smoke on acceleration so immediately thought it was a split intercooler hose. Had a look but can't see anything, need to spend a decent amount of time stripping and cleaning them to be sure there are no holes.

My question is... On looking under the bonnet after the light came on I noticed there is a fair amount of oil on the block and it is coming from the crankcase breather. Would the lack of boost cause this or am I looking at another problem?

Thanks in advance.


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The 1.8 goes way back, into the mists of time....yes, the crankcase oil breather can often be dirty/ oily, its unlikely to be the turbo underboost

When you buy a car the engine bay is often valeted, the oily breather could have been there before but you could not see it and it has built up again over time

if any engine needed a breather catchtank - thats it

PS - the breather cannot normally affect the turbo either, as its upstream of the compressor (at about atmospheric pressure)

edit - worn bores, rings or valve guides can cause piston blow-by, this can cause a biuild up of pressure in the crankcase, that can force the oily gasses out of the breather hoses, its ok at an acceptable level, but eventually you can lose compression in one or more of the cylinders and/ or burst the crank(etc) seals, and the oil consumption can go up, the engine oil can become contaminated and the emmisions can go up, and the exhaust can smell of burnt oil (on a petrol-engined car, this could fail an MOT, but on a diesel, as long as its not too smokey, it should be ok) as before, no need to be unduly concerned, as some engines seem to get dirty/ oily round the breathers

A compression test may be a good idea - and will give an ingication about the condition of the bores/ rings etc

Again, a catchtank is a realatively low cost temporary solution to "fix" this

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