MINI Cooper Valve cover gasket replacement & Spark plug tube seal replacement.
As with many things, everything is much clearer in hindsight. A work colleague stopped me in the parking lot one day and mentioned he smelled an odor coming from my R53, but I didn’t pick up on the clue. Later, as I was trying to find the source of an oil leak, if finally dawned on me that I should examine the valve cover gasket for a leak (or cylinder head cover gasket in MINI speak) as it can cause a burning oil smell but not cause any drips that help show where the leak is coming from.
The valve cover gaskets and spark plug tube seals (spark plug tube grommets) are known to leak on MINI’s and should be checked and replaced as the mileage starts to get up there.
The valve cover gasket keeps oil from leaking out of the cylinder head while the car is running – the oil will drain out of the head when the car is off, so leaks here are usually worse when the car is running. What makes this problem so tricky on the MINI is that the engine is tilted about 10 degrees to the back, so a leaking valve cover gasket is likely to allow oil to ooze down the back of the block and onto the exhaust manifold, where the oil will usually vaporize – eliminating evidence of the oil leak. The oil vaporizing off the exhaust is the source of the burnt oil smell or burning oil smell associated with this problem.
The gaskets are not expensive. You can save yourself some labor by replacing the valve cover gasket and the spark plug tube seals at the same time, as the procedure is almost identical. It is not a hard or lengthy job, but does require removing the valve cover. If your car is getting up there in miles or age, it is probably a good time to inspect the bolts and grommets on the valve cover as well. They are replaceable and can be popped out with a finger or a blunt tool once you have the valve cover off.
The spark plug tube seal prevents oil from migrating from inside the valve cover to the spark plug tube and preserves the vacuum inside the cylinder head – if oil gets into the spark plug tubes, it will accumulate there as there is no way for it to drain out. One obvious sign of a leaking spark plug tube seal is a build up of oil in the spark plug tube – which can also appear as oil on the outside of the spark plugs or oily spark plug boots.
Besides the obvious problems with leaking oil, failed valve cover seals act as an engine vacuum leak that can reduce fuel mileage, reduce performance and occasionally generate engine codes as the computer tries to accommodate the vacuum leak by adjusting the mixture.
If you catch a leaking spark plug tube seal early, and the plug boots haven’t deteriorated, you can avoid having to replace the wires. If the wires are saturated with oil, they should be replaced and the oil residue cleaned off the spark plugs or the spark plugs replaced as well. Clean up the excess oil (since it traps dirt and grime) before removing the spark plugs or removing the valve cover.
The PCV valve is mounted to the right side (passenger side) of the valve cover and has to be removed as part of the procedure to remove the valve cover. The early ones are held in with a single screw. Later ones thread in. Later generation MINI’s do not have a removable PCV valve. One the first generation MINI’s the PCV valve is quite simple - it is essentially a check valve with a spring and ball inside.
As a quick check, you can shake it gently once it is off the car and listen to confirm the check valve is free to move (you should hear the ball move). You can also gently blow on it from each end to make sure it allows flow out of the valve cover but doesn’t allow flow in (using a short section of rubber hose keeps residual engine oil out of your mouth…). A stuck or obstructed PCV valve is one cause of moisture accumulation in an engine and the formation of oil sludge.
The valve cover bolts tend to corrode pretty quickly on MINI’s, so it is advisable to replace them if they are starting to look weak. Hopefully they aren’t too far gone as some owners have had to deal with broken off bolts that were weakened by corrosion. You will notice these are special sealing bolts that capture a grommet. In addition to the 8 short sealing bolts, there are 4 long sealing bolts that have a threaded stud that sticks up to help hold the wiring harness. The original designs for these bolts are a little longer than needed and also hard to remove – as they are longer than many 8mm deep sockets. The new version is a little shorter and can be removed with most 8mm deep sockets, which is another good reason to replace them.
As you put it back together, remember to torque the valve cover bolts correctly and not over tighten them. The torque value for the valve cover bolts is 12 Nm (9 ft-lbs). Tighten them from the center outward in an expanding circle, just as you would tighten head bolts.
Make sure to press the spark plug boots all the way down until they click onto the top of the spark plugs.
Other parts you will be removing and may want to replace or upgrade during this procedure:
General Procedure for R53 valve cover gasket (similar for R50):
The valve cover can be removed and replaced without lifting or jacking up the car. Ignition should be off and the engine cool.
1) Remove 4 torx bolts securing intercooler cover. Tighten to 9 Nm (7 ft-lb) when reattaching.
2) Remove 4 bolts holding the frontward intercooler mounting brackets (this gives you more room to remove intercooler). Tighten to 9 Nm (7 ft-lb) when reattaching.
3) Remove 8 torx bolts holding intercooler bellows clamps and remove the clamps. Tighten to 9 Nm (7 ft-lb) when reattaching.
4) Remove intercooler bellows (inspect for damage, they degrade over time and will cause very poor performance if damaged). Now is the time to replace them with stock or upgraded bellows if they don’t look good.
5) Lift intercooler out and set aside being careful not to damage fins.
6) Remove the left and right intercooler mounting brackets. A 12” extension on a socket helps a great deal. Tighten to 9 Nm (7 ft-lb) when reattaching.
7) Disconnect the electrical connector on the rear of the ignition coil pack. This connector requires a two step process to remove don’t try to muscle it off – slide the securing clip sideways before pulling the connector off (pulling towards the rear of the vehicle). The coil pack can remain bolted to the valve cover unless you are replacing the coil pack.
8) Disconnect the two hoses used for crankcase ventilation that attach to the valve cover.
9) Pull straight up on spark plug boots to disconnect from spark plugs. Wiggle/turn slightly side to side to help free them if stuck. A plastic pry bar can help.
10) Clean around the cover and spark plug tubes before removing them to minimize the grime that can fall into your cylinder head. Paper towels or shop rags work well for this.
11) Identify the extra long valve cover bolts and slide the wiring harness clips off the bolts. Sketch a map or snap a photo so you can put them back the correct way.
12) Remove 12 valve cover bolts. Tighten to 12 Nm (9 ft-lb) when reattaching.
13) Remove valve cover by lifting up.
14) Be extra careful not to drop dirt or tools into the open cylinder head.
15) The valve cover gasket and spark plug seals can be removed with your fingers or a blunt tool. Clean all the sealing surfaces, lightly oil the new seals and reinstall.
16) Reassembly is the reverse - carefully inspect your intercooler boots before tightening the clamps, as a leak due to being installed folded or crooked or a tear will cause very poor performance. An inspection mirror makes it easier to check that the bottom side is sitting flat.