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N14 Engine Important Maintenance Items and Common Issues

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N14 Engine Important Maintenance Items and Common Issues

Old 09-21-2017, 07:54 AM
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N14 Engine Important Maintenance Items and Common Issues

The N14 engine was Mini's first Direct Injected engine. It suffers from a few well known issues:

1) Carbon build up on the intake valves. In engines where the fuel injection occurs in the throttle body or in the intake port, the vaporized fuel passing over the valves plays an important role in keeping them clean. In a DI engine the fuel is injected into the cylinder, so there's nothing to clean the valves. With no fuel to clean the valves, oil vapor from the PCV system causes carbon build up on the valves, eventually causing poor engine performance. The solution is to clean the intake valves, typically done by blasting with crushed walnut shells. This may need to be done as often as every 30K miles. A popular mod to help combat carbon buildup is an oil catch can (OCC) which is intended to separate the oil vapor out of the PCV system. There is also an updated valve cover design that does a better job of separating the oil out and returning it to the engine, which reduces carbon build up.

2) Timing chain / timing chain tensioner. Like most modern engines, the N14 engine is an "interference" engine, meaning that the pistons and valves have to be properly synchronized or they'll try to occupy the same space at the same time, with catastrophic results. On early N14 engines the timing chain tensioner failed, causing the timing chain to stretch and then fail. The early symptom of this is often referred to as the "death rattle." Mini had a campaign to check and replace timing chains and tensioners, an important thing to look for when purchasing a used Gen2 with the N14 engine is whether the timing chain and tensioner have been replaced. If the death rattle occurs, it is important to check the timing chain guides as they are plastic and often break and end up in the oil pan where the pieces can cause problems with the oil pump.

3) Maintaining the oil level. This is critical to engine life, not just for lubrication but also for the timing chain tensioner and for the VANOS system which adjusts the intake valve timing. N14 engines have a reputation for high oil consumption, sometimes as high as 1 quart in 1000 miles. Check the oil every time you fill up with gas.

4) Vacuum pump failures. The N14 engine has a vacuum pump (for the brake booster and turbo wastegate control) that is driven off the end of the exhaust camshaft. If the vacuum pump seizes, it tends to take the engine with it by breaking the timing chain and then valves and pistons collide. Maintaining oil level is important. Replacing the vacuum pump at 100K miles is a popular preventative maintenance item.

5) Thermostat: Leaks from the thermostat housing/gasket are common on engines over 75K miles. Also the coolant cross over pipe between the water pump and the thermostat becomes brittle and fragile and the seals can fail with age.

6) Turbo Oil Line: Failures of the gaskets and connections on the oil line to the turbo are another common problem for high mileage engines. The pressure side line starts to leak oil onto the hot turbo, resulting in smoke from under the hood. NAM forum vendors have upgraded oil line kits with improved hoses, connectors, and washers. Plenty of threads on how to DIY this.

7) Valve Cover: Make sure you don't have a bad valve cover, the internal built in PCV is known to stick open and consume oil. An updated design is available, see this thread: https://www.northamericanmotoring.co...over-leak.html

8) High Pressure Fuel Pump (HPFP): Unfortunately there isn't any maintenance to make your HPFP last a long time, when it goes it's gone and needs replacing. (There is a thread in the Stock Problems/Issues forum where some brave Mini owners are experimenting to learn how to rebuild the HPFP.)

9) Turbo Diverter/Recirculator Valve: This is a valve mounted on the turbo that opens to allow the boost pressure developed by the turbo to spin around inside the turbo when the throttle is suddenly closed, such as when shifting gears. This prevents stalling the turbo from sudden pressure spikes and keeps the turbo spinning to help maintain boost across shifts. It is common for the rubber diaphragm in the valve to tear, causing loss of boost and various trouble codes. Fortunately it is simple and relatively inexpensive to replace the valve, there is an updated design available that is much more robust.

Last edited by squawSkiBum; 03-15-2019 at 09:35 PM. Reason: added item 9)
Old 03-15-2019, 09:37 PM
squawSkiBum is offline
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Originally Posted by I like mini clubman's View Post
Coolant crossover pipe needs replacement at 60 to 80,000 miles
valve seals toast after 80,00 miles
Added a note about the coolant crossover pipe, thanks for the suggestion. Got any links regarding the valve seals?
Old 03-16-2019, 06:16 AM
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No links for the valve seals. I pulled the head from my n14 with about 85,000 miles and all the seals were burnt up. Engines run too hot as far as I'm concerned. My engine had the timing chain failure and I pulled the head to check for bent valves. It was also plugged solid with carbon and gunk from the pcv system and leaking valve seals.
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