Where did my oil go?
#26
11-11-2019, 06:19 PM
A few things from what I've read so far:
You can't compare an N12 engine with a N14 engine, the N14 engine is turbocharged and the N12 engine is not, they have different PCV systems and the N14 is direct injected and the N12 is port injected, Apples and oranges.
The turbochargers on second generation MINI's don't have oil seals, they rely on a very close tolerance bearing, you can easily check this bearing by taking the rubber hose off of the turbocharger compressor inlet, grab the center of the compressor wheel and try to move it axially and radially, there should be no play and it should spin easily.
There are two one way valves in the N14 head cover, the one on the back of the cover prevents boost pressure from the throttle body from pressurizing the crankcase, the other allows crankcase gasses to vent to the turbocharger inlet when the engine is under boost. In normal operation, when the intake manifold is under vacuum, crankcase gasses are vented to the throttle body, and are vented to the turbocharger inlet when under boost.
If the one way valve to the turbocharger fails closed and boost pressure is allowed into the crankcase, it will cause oil leaks all over the engine. If it fails open, every time your engine is in boost, it will blow oil in through the turbocharger compressor.
The PCV valves are integral with the head cover. I think that you need a new head cover.
You can't compare an N12 engine with a N14 engine, the N14 engine is turbocharged and the N12 engine is not, they have different PCV systems and the N14 is direct injected and the N12 is port injected, Apples and oranges.
The turbochargers on second generation MINI's don't have oil seals, they rely on a very close tolerance bearing, you can easily check this bearing by taking the rubber hose off of the turbocharger compressor inlet, grab the center of the compressor wheel and try to move it axially and radially, there should be no play and it should spin easily.
There are two one way valves in the N14 head cover, the one on the back of the cover prevents boost pressure from the throttle body from pressurizing the crankcase, the other allows crankcase gasses to vent to the turbocharger inlet when the engine is under boost. In normal operation, when the intake manifold is under vacuum, crankcase gasses are vented to the throttle body, and are vented to the turbocharger inlet when under boost.
If the one way valve to the turbocharger fails closed and boost pressure is allowed into the crankcase, it will cause oil leaks all over the engine. If it fails open, every time your engine is in boost, it will blow oil in through the turbocharger compressor.
The PCV valves are integral with the head cover. I think that you need a new head cover.
I only addressed the N14 head covers. They changed the head on the N18 engines, it has internal ports in the cylinder head to vent crankcase gasses into the intake ports, eliminating the PCV line to the throttle body, you can't compare N18 heads and head covers with N14 heads and covers. One advantage of the N18 head is that it greatly reduced carbon build up on the exhaust valves.
It still has PCV gasses passing through the back of the valve cover which is using surface area and a cold spot to trap the oil vapors. I finally found the coked oil you are referring to re the intake right there.
Still begs my question and the OP question. Where is that quart of oil every 1000 miles going?
#28
10-31-2021, 12:07 AM
I finally got round to fixing this. A compression test showed exactly the same pressure across all cylinders (not just within 10%, it was virtually identical) so that got me excited as it meant I didn't have big issues with ring seals so this might be a cheap fix.
I have been running an eBay valve cover and gasket. Over time it started to get very slightly oily on the valve cover especially around the plugs. Of late the oil has gotten worse and I started to get misfires occasionally when the engine is first started. Oil consumption has also been getting worse and I started to have a smoky exhaust especially after being idle for a few minutes while waiting for the wife, or an especially long stop light. I initially thought that might be because I developed an oil leak in the turbo and it was dripping oil on idle (turbos generally have dynamic sealing so it seals better when under boost).
I decided to buy another eBay valve cover but use original Mini gaskets this time. I also cleaned the oily plugs and coils. All the problems went away including the original oil consumption. My oil has remained at the same level over last 2000 miles. If I had to guess... the gaskets around the spark plug were leaking oil into the engine causing oil loss. When it was bad enough, it fouled the plugs and caused misfires.
It might also have something to do with the previous valve cover. With the previous valve cover, the crankcase pressure seemed excessively high, I even had oil shooting out from my dip stick tube if I used aftermarket dip sticks which didn't seal as tightly as the factory one.
I have been running an eBay valve cover and gasket. Over time it started to get very slightly oily on the valve cover especially around the plugs. Of late the oil has gotten worse and I started to get misfires occasionally when the engine is first started. Oil consumption has also been getting worse and I started to have a smoky exhaust especially after being idle for a few minutes while waiting for the wife, or an especially long stop light. I initially thought that might be because I developed an oil leak in the turbo and it was dripping oil on idle (turbos generally have dynamic sealing so it seals better when under boost).
I decided to buy another eBay valve cover but use original Mini gaskets this time. I also cleaned the oily plugs and coils. All the problems went away including the original oil consumption. My oil has remained at the same level over last 2000 miles. If I had to guess... the gaskets around the spark plug were leaking oil into the engine causing oil loss. When it was bad enough, it fouled the plugs and caused misfires.
It might also have something to do with the previous valve cover. With the previous valve cover, the crankcase pressure seemed excessively high, I even had oil shooting out from my dip stick tube if I used aftermarket dip sticks which didn't seal as tightly as the factory one.
Last edited by hxkenneth; 10-31-2021 at 12:22 AM.
#29
11-07-2021, 05:52 AM
1st Gear
Fixed my 'justa' high oil consumption by replacing the 'one piece oil' control rings fitted act standard to the Prince engine with a more common 'three piece' oil control ring. Went from 1 litre every 800 miles to zero oil consumption. Now with the turbo mini there is chance that oil is being burnt via the turbo but I'll put money on the oil control rings being at the heart of the problem. Sorry its not simple swap a 'rubber membrane' fix, you need to lift the head and drop the sump fix - pull out the pistons.
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