Seized by Police?

▶ As has been reported by some of the mainstream media, the police have been having major issues with N57 3-litre diesel engines, as fitted to some BMW 3- and 5-Series cars and X5 4x4s made between 2017 and 2020. 2021-on cars have different engines and aren’t, apparently, affected.

What happens is that number four conrod goes through the block due to main bearing failure, but the engine carries on running on five cylinders pumping oil out on to the hot engine as it does so. Then the oil catches fire.

There have been several cases of this happening including one in 2020 when, tragically, an officer in Cumbria who was responding to an emergency call was killed when a BMW engine failed in this way.

Following this, some forces withdrew cars with this engine from service completely, while others restricted them to light duties only and banned them from being driven over 90mph, or 20mph over any other statutory speed limit. Police Scotland, at one point, had no fewer than 130 affected cars either out of service completely or restricted to low-speed operation.

It’s been suggested that the base cause of the problem isn’t so much high-speed use as the engines being left running at idle for hours on end to keep battery-power up while attending emergencies with all lights activated, etc. Responsibility for the failures is, however, disputed. The police are saying that BMW’S engines aren’t up to the job. BMW, however, say it’s down to the hard use made by the police, and are adamant that it “did not merit action on any civilian vehicles.”

Now, numerous affected cars are going to auction, and to avoid any legal or moral responsibility for any that might catch fire after sale, many police forces are deliberately seizing the engines of affected cars prior to sale, so they have to be renewed. The ‘seizing’ process involves draining engine oil, replacing it with Sodium Silicate and then running them until heat then causes the Sodium Silicate to weld the internals together.

It’s very effective, too. Make no mistake about it, an engine which has had this treatment is 100% scrap, will not be repairable or even contain any reusable parts. We’ve heard of someone who bought one recently and couldn’t even turn it to undo the flywheel bolts – even the turbocharger had seized solid!

At present, there are a few replacement engines around – but these need treating with caution as in the recent past some police forces have sold running cars as salvage due to this problem, and some engines that have been removed are probably still in circulation and could fail at any time. Reconditioning specialists are also offering rebuilds from around £3000, but that’s applicable only if your existing engine is suitable for rebuilding, which one that’s had a rod through the block side or been seized deliberately won’t be.

My advice, frankly, is to avoid buying any of these cars as ex-police vehicles – the risks, and not just risks of mechanical failure, are just too great. At present there doesn’t seem to be an issue with cars that have not been used by the emergency services, though in the past it’s not been uncommon for police car failures to affect non-police cars a few years later.