BMW 320i Engine Seizure (N20) - Fault Finding. Found!

[Stevan]

In August 2018, i purchased a BMW 320i sport from a private seller. Full service history, regular services, recent MOT.
Upon a test drive, and paying to have a mechanice inspect the vehicle i purchased the car for £6500. It had 70k on the clock.

A week later after noticing a faint noise, and smoke upon start up, i scheduled a trip to a garage. I got a mile from the garage before the engine seized with an almighty scream.

I had the car towed to the garage, and a day later i had a phone call telling me 'Ill need a new engine'.

I rang around, and engines were £2500 plus £1000 fitting. I then rang around and found a couple of garages who quoted me on a rebuild.

At this point, no one knew the fault with the car, and an argument had been made from different engineers who had advised that the N20 (despite being a brilliant engine) had some seriously awful common faults, and that swapping the engine should only be seen as a good temporary fix, but long term - 'wouldnt be an ideal solution'.

I decided to rebuild the engine, and braced myself for a costly fix. A nice bunch of engineers gave me a quote to fix the car (just fix the problem if i pay for parts) that was half the cost of an engine.

Engineers took the car from the garage, and proceeded to take the engine apart, after a week, the diagnosis, was intitially, an oil inlet valve (£30), a con-rod (£220 used) and a new crank (£600 used). The oil inlet valve had become seized and stopped the bottom of the engine from getting its feed of oil. The feint knocking was where the crank, had ground with an un-oiled con-rod (cylinder 3) and had damaged the thrust face.
I asked the engineers to fit a timing chain while they were in the engine. This brought the labour cost to £2000 (plus the parts id purchased)

Once these items were replaced, it was advised that i should replace the oil pump while in the engine. A cost of £1000 (plus vat) was wanting for the oil pump. A diminishing bank balance, meant i had to look to start saving costs.
After calling around, A BMW specialist offered to do the work (theyd also given me a quote originally for £2500 just to diagnose the engine problem from a rebuild) for £550 (including vat), They warned me that they hadnt worked on many N20's and they havent alot of experience with the F30- but assured me it was no trouble. I had the engineers put the engine back together and thanked them for the work.
Once the engine was put back together, the engineers called me and explained that the Oil Pump had indeed failed- It was pumping 25% less oil than it was supposed to- They advised me not to run the engine, until it got to the BMW specialist, So i had the car towed at a cost to the Specialist and this is where things got bad.

After long drawn out conversations with the BMW specialists in Bury, Manchester. I booked in the car for the oil pump, and then recieved a phone call.. 'Its not the oil pump its the Oil inlet valve. We want £100 to fix it'.
I explained that this had been replaced. 'Well our machine says its the oil inlet valve, ill have another look'.
There was a day between phonecalls, before they once responded again 'Yeah, we think its the Oil pressure switch'.

I agreed to let them replace it before they called me back 'That hasnt worked, so were gonna replace the oil pump'.

I frustratingly argued with them, before i subsided and decided (Its only an extra £100). But then, a week later i get a phone call 'Hi its your car, weve been running your car for a while, its smoking and it sounds like a type writer. We dont want to fit the oil pump. Can you come pay and collect your car'.
After 15 minutes of arguing with the really poorly trained woman on the phone, she says she wants paying for the work theyve done before im allowed to have it back.

After a phone call to the engineers, i paid them and sent it back on the same tow truck to the place it came from.

The engineers inspected the engine, and went back to work. At this point the engineers, were very understanding and everything 'was no trouble'.
A phone call came in 'Really sorry to say, but from experience, i think youll want to have your turbo serviced/repaired, the car is smoking and the likelihood is that its about to fail. You risk another seized engine'.

They then took the engine out, and had the oil pump fit and the turbo serviced. At another cost of £2000.

Their diagnosis was that the oil pressure sensor didnt detect a sudden dangerous drop in oil pressure (apparently a 0.1 of a bar and the warning would have come up on the dash)'- As the oil pump was mechanical (the only thing that puts pressure into the pump is a spring, which over time loses tension and the chain that drives the pump) the 25% drop in oil pressure meant the engine was receiving 25% less oil and had been like this for the last few thousand miles.
The turbo had been starved of oil, and the oil inlet valve had built up with sludge as the pressure wasnt there to push into the bottom of the engine.
The engineer assumed that the car had been filled up with thicker oil, and had been run for a while just before it had been sold.
His thoughts were that this seller knew about the pump and the damage that had been done. Hence why it was sold cheaply.

So, always buy an N20 thats had a sheduled Oil Pump change!
Or get one from a dealer with a good Warranty!

And never use BMW specialists who use apprentices to fit oil pumps!

TLDR: Car seized and became smokey because of a faulty oil pump damaging the turbo, and starving the engine of oil.
https://imgur.com/a/bw4uUkT