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N14 Engine Important Maintenance Items and Common Issues

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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.

2) Timing chain / timing chain tensioner. 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.

3) Maintaining the oil level. This is critical to engine life, both for lubrication 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.

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) 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...lve-cover.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.)

Last edited by squawSkiBum; 02-26-2018 at 06:21 PM. Reason: thread cleanup
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