I Blew Up My BMW N54 Engine – Removing & Replacing

After “sending it” at 30psi for a couple hundred miles, I developed a misfire. I narrowed it down to cylinder 3, but wasn’t sure if it was plugs, coils, injectors, etc. I swapped all accessories between cylinders, but nothing would follow. That’s when I started to get worried.

Without wasting any more time, I busted out the compression tester. The results were disappointing.

Cylinder 1: 170 psi
Cylinder 2: 170 psi
Cylinder 3: 80 psi
Cylinder 4: 170 psi
Cylinder 5: 170 psi
Cylinder 6: 170 psi

I’m not sure what exactly caused the problem, but adding a tablespoon of oil down the cylinder boosted compression back up. 99% sure it is a cracked ring or a chipped ringland. If I had to guess, the car developed a misfire but I was too greedy and stayed on the throttle while it was a misfiring for a couple pulls. Or maybe it just randomly gave up… I’ll never know why. The logs looked good before the misfire, but I knew I was playing with fire at this power level.

After saving up for a few months, I bought a used motor from a junkyard. It came out of a 2008 335i 6MT with 91,223 miles. The car was hit pretty hard on the driver’s side, so I’m not worried about flood damage or anything like that. It was also modified, so I’m hoping it was taken care of by an enthusiast.

I put it on my engine stand and noticed it had all index 11 injectors, an RB PCV valve/cap, and it looks spotless under the oil cap. No sludge, grime, buildup, or discoloration. Hoping this is a sign of frequent oil changes.

Next step was removing the blown motor from my car. I started by taking the whole front clip off. Drained oil and coolant. Removed intake, intercooler, intake manifold, injector and coil harness, disconnected coolant lines, vacuum lines, electrical clips, etc.

Disconnected a few more things and it was free. N54 delete.

Man, it hurt to remove those MMP Stage 3 turbos that I JUST finished installing…

Now that I had the damaged motor out of the car, I focused my attention on the new motor. I wanted to get it up to par before installing it. I replaced the valve cover & gasket along with the oil pan gasket.  Replacing these things meant I got to look inside the engine. Everything looked great, absolutely no sludge or grime.

I swapped over my index 12 injectors, low-mileage water pump, HPFP, oil filter housing, tensioner, pullies, etc. Then I broke out my walnut blasting tools so I could get the intake valves nice and clean. If you need to clean your intake valves, read my DIY tutorial.

Before:

After:

After some consideration, I decided this was the perfect opportunity for me to switch up my turbo setup. Instead of cluttering this post, check out my next post that explains my reasons for ditching my MMP Stage 3 twin turbos for a Doc Race single turbo kit.

That’s right – this beautiful kit is on the way to my doorstep…

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