The plenum problem should not affect compression tests. It allows oil to get sucked into the intake and will cause carbon buildup, plug fouling, and pinging. If you have zero compression on a cylinder, it is usually a valve problem. Even a burned piston will make some compression, unless it has a big hole in the middle.
Sorry, but if your compression results are to be trusted (and it seems they are), then you have to tear a head off to find the problem, or at least get a borescope in it.
It often means that you are burning antifreeze. You asked if it needs antifreeze, have you noticed any leaking out of the reservoir tank while you are running it? Sometimes when the head gasket goes it will produce a passage for the antifreeze to pass from the capillaries into the combustion chamber. It is easy to check if you have an air compressor. Remove one of the rear sparkplugs and the radiator cap. Fill the radiator and then push some air into the sparkplug hole (get a good seal in case a valve is open). Repeat with all the cylinders and watch for air bubbles coming up into the radiator. If bubbles come up or fluid is pumped out, the head gasket is blown and must be replaced. It is more likely to happen at the back of the engine because it is farthest away from the fan and therefore gets less cooling.
Also check your oil for discoloration. If it is a brownish color it could mean your oil and antifreeze are mixing and has the potential to damage your bearings
my 2003 accent is having the same oil issue. it is not leaking, it is just sucking through oil at a superspeed.
hardly likely the exhaust job would cause that, but yes it sounds like you got a blown head gasket. badl lock stricks hmm! also preasure test cylinder head for leaks
the engine for several minutes at idle. Turn the engine off and let it
sit for about 15 minutes. Restart the engine and immediately increase
the engine speed while observing the exhaust. If a heavy billow of
bluish smoke is exhausted then disappears and the exhaust remains
relatively clean, the most likely cause is excessive valve guide wear.
In this case, the valve guides or valve guide seals require service. If
the above test only produces mild smoke and the smoke remains at the
same level during all operating conditions, the piston rings will have
to be tested. This is done by performing a compression test on the
engine. The first test is referred to as a "dry test" and the second
test is referred to as a "wet test". The dry test consists of measuring
the engines compression using a compression tester installed in the
spark plug hole and the ignition system disabled. The engine is then
cranked and the pressure is measured and recorded. A few teaspoons full
of oil is then poured into the spark plug hole and the compression is
then measured again. If the reading increases more than 15 PSI, the
rings are worn and major engine service is probably required.
This is quite a common problem,especially with the 2.2 dci engine,although as usual Renault wont admit the problem.The reason your engine throws the oil after a run and not when stationary is this problem is caused by the turbo pressurising the crankcase.You can rev the engine all day but when theres no load on it then the turbo is not working at full pressure and all is well.
The cure for the problem is to fit a new rocker cover which incorporates part of the inlet manifold.The breathing system on these engines is complicated and the rocker cover has to handle both inlet gases AND exhaust gases and although no one can explain why a new cover cures it,I suspect the plastic the cover is made of is not robust enough and either becomes porous or warped and this allows gases into the crankcase,pressurising it and focing oil out either through the dipstick or it blows out the blanking plug in the timing cover.
It is not a massive job to replace the rocker cover as long as the injectors come out easily.If they dont then youre in real trouble.Good luck,Duncan.