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N14 Engine Important Maintenance Items

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Old 09-21-2017, 07:54 AM
squawSkiBum squawSkiBum is offline
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N14 Engine Important Maintenance Items

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.

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.
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Old 10-09-2017, 08:42 PM
squawSkiBum squawSkiBum is offline
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Continuing with N14 engine maintenance items:

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.
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Old 10-13-2017, 09:18 PM
AutoCoarsen AutoCoarsen is offline
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My vacuum pump seized at 94,000 miles and wrecked an engine. I’m replacing every 50,000 miles. Easy access and not too expensive.
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Old 10-16-2017, 12:25 PM
tyr tyr is offline
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Quote:
Originally Posted by AutoCoarsen View Post
My vacuum pump seized at 94,000 miles and wrecked an engine. I’m replacing every 50,000 miles. Easy access and not too expensive.
This happened to the one I just picked up as well (it was at 130k miles, but it failing caused the exhaust camshaft bolt to shear off into the timing belt causing 2 bent exhaust valves in the process).

Seems like it is more common than you would think...
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