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BMW 1 Series: B47 Diesel EGR Bypass Pipe Cracking and Coolant Loss

B47 Diesel EGR Bypass Pipe Cracking and Coolant Loss is a common cooling fault on the BMW 1 Series on the 2015–2019 cars, and we rate it major. Putting it right costs $600 to $1,800 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 50 documented faults on the BMW 1 Series.

Vehicle
BMW 1 Series
Engine
B47
Years
2015–2019
Fuel
diesel
System
Cooling

This page covers the BMW 1 Series as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All BMW 1 Series faults50 documented faults on this model

What you are looking at

No photograph available

We do not hold a verified photograph of the EGR valve yet. We would rather show none than show a picture of a different part.

What goes wrong

The B47D20 diesel engine's EGR (Exhaust Gas Recirculation) cooler bypass pipe is a known failure point. The aluminium pipe develops cracks at the weld joints due to thermal cycling, causing coolant to leak into the exhaust or intake tract. This can result in hydrolock if coolant enters the combustion chamber in sufficient quantity. BMW issued a parts upgrade (revised pipe design) but many vehicles remain on original parts.

What you would notice

  • Coolant level dropping without visible external leak
  • White or sweet-smelling smoke from exhaust, especially on startup
  • White residue or staining around EGR pipe weld joints
  • Coolant warning light or low coolant message on iDrive
  • Rough running or misfires if coolant enters combustion chamber

How to check it

Where to look. Rear of engine, EGR cooler bypass circuit, near firewall

  1. Inspect the EGR bypass pipe at the rear of the engine near the firewall for white residue, coolant staining, or wet areas around weld joints.

  2. Check coolant reservoir level and note if it requires regular top-up.

  3. Look for white smoke from exhaust on startup (coolant combustion).

  4. Scan for fault codes related to EGR or coolant temperature sensors.

Parts involved: EGR valve.

What it costs to put right

$600 to $1,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

  • “Has the EGR bypass pipe or EGR cooler ever been replaced or inspected for cracks?”
  • “Does the coolant level ever need topping up between services?”
  • “Has white smoke ever been visible from the exhaust on a cold start?”

Now check the BMW 1 Series you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

BMW 1 Series buyer questions

Is b47 diesel egr bypass pipe cracking and coolant loss serious on a BMW 1 Series?

We rate it major and common on the BMW 1 Series. The B47D20 diesel engine's EGR (Exhaust Gas Recirculation) cooler bypass pipe is a known failure point. The aluminium pipe develops cracks at the weld joints due to thermal cycling, causing coolant to leak into the exhaust or intake tract. This can result in hydrolock if coolant enters the combustion chamber in sufficient quantity. BMW issued a parts upgrade (revised pipe design) but many vehicles remain on original parts.

How much does it cost to fix on a BMW 1 Series?

$600 to $1,800 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which BMW 1 Series years are affected?

Our research records this fault on the 2015–2019 BMW 1 Series. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Inspect the EGR bypass pipe at the rear of the engine near the firewall for white residue, coolant staining, or wet areas around weld joints. Check coolant reservoir level and note if it requires regular top-up. Look for white smoke from exhaust on startup (coolant combustion). Scan for fault codes related to EGR or coolant temperature sensors. Look here: Rear of engine, EGR cooler bypass circuit, near firewall