Models · BMW
BMW M135i and M140i F20/F21 buying guide
The six-cylinder 1 Series hatchbacks: the M135i from 2012 with the N55 turbo straight six, and the M140i from 2016 with the B58. Both came as three-door and five-door cars with rear-wheel drive and a manual or automatic gearbox.
The versions
- M135i (2012 to 2016): 3.0 turbo straight six (N55), 320PS, 326PS after the 2015 facelift
- M140i (2016 to 2019): 3.0 turbo straight six (B58), 340PS
- 6-speed manual or 8-speed ZF automatic; the manual was dropped from the M140i around July 2018
- Rear-wheel drive in the UK, with an open differential as standard and a limited-slip differential as a factory option on the M135i
- Three-door (F21) and five-door (F20) hatchbacks
What to check on a M135i or M140i
3 model-specific things to look at when you view one. They're a starting point, not the full inspection.
Whine from the automatic gearbox
What to look for: On an automatic, drive through all the gears gently and then under firmer acceleration, and reverse a short distance. Listen for a whine in second, fourth or reverse.
Why it matters: A whine in those gears can be a sign of a gearbox on its way out, and a replacement unit is a major job. Most automatics are fine; this is the one noise to rule out on the drive.
Coolant level on the M140i
What to look for: With the engine cold, check the level in the coolant expansion tank and look for dried coolant residue around the cap and tank. Ask whether the seller has had to top it up.
Why it matters: Pre-facelift M140i cars can lose coolant gradually with no obvious leak, and the filler cap is the leading suspect. It's a simple fix, and a car whose owner has checked it regularly is a sign of one that's been looked after.
Rattle or sticking from the exhaust valve
What to look for: Listen at the back of the car at idle and as the revs rise and fall. Switch between driving modes and listen for the exhaust note changing. A rattle from the back box, or no change at all, is the thing to note.
Why it matters: The M140i's exhaust valve can rattle, seize or fail. BMW usually replaced it under warranty, so ask whether it has been done.
Also in the full guide
- Stiff steering after standing
- Split charge pipes and the N55's oil leaks
- Stone damage to the M140i's chargecooler
- Differential and gearbox oil
- The cold start, test drive and paperwork checks for the exact version you're viewing
The full guide to the M135i or M140i
The CrankSight guide walks you round the car on your phone at the viewing, with every check for the exact version you're looking at: what to look for, where to find it, and what anything you find is likely to cost. As you go it builds an assessment of that car, and if you view more than one, it lines them up side by side.
£29 for the model, used on as many cars as you like, delivered within 72 hours or your money back.
General points for the model, last checked October 2026. Every car is different, so treat this as a guide to what to look at, not a verdict on any car. CrankSight is independent and has no connection with BMW.