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Volkswagen Golf: IS38 Diverter Valve Failure – Boost Leak Under Pressure (Golf R Mk7/7.5)

IS38 Diverter Valve Failure – Boost Leak Under Pressure (Golf R Mk7/7.5) is a common engine fault on the Volkswagen Golf on the 2014–2020 cars, and we rate it major. Putting it right costs $180 to $480 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 49 documented faults on the Volkswagen Golf.

Vehicle
Volkswagen Golf
Only on
Golf R / R32
Years
2014–2020
Fuel
petrol
System
Engine

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

All Volkswagen Golf faults49 documented faults on this model

What you are looking at

No photograph available

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

What goes wrong

The IS38 turbocharger fitted to the Golf R Mk7/7.5 uses a recirculation diverter valve (DV) that is known to fail under the higher boost pressures of the IS38 compared to the IS20. The internal membrane/piston degrades and allows boost to escape, causing a characteristic flutter or hissing sound and measurable power loss. Failure rate is accelerated on cars running a Stage 1 tune due to elevated boost. Widely documented across Golf R forums and confirmed by aftermarket manufacturers.

What you would notice

  • Flutter, chirp, or hissing sound from engine bay under boost
  • Noticeable power loss above 3,000 rpm
  • P0299 underboost fault code
  • Boost gauge showing lower than expected pressure
  • Worse fuel consumption under load

How to check it

Where to look. IS38 turbocharger compressor housing, passenger side of engine bay

  1. Inspect the IS38 diverter valve for external cracks or deformation.

  2. Apply vacuum and hold to test the valve membrane integrity.

  3. Scan for P0299 or boost-related codes.

  4. Listen for boost flutter on hard acceleration from 2,500 rpm.

Parts involved: Turbocharger.

What it costs to put right

$180 to $480 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 diverter valve ever been replaced on this car?”
  • “Has the car been tuned – Stage 1 or higher?”
  • “Has the car ever shown a P0299 underboost code?”

Now check the Volkswagen Golf 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.

Volkswagen Golf buyer questions

Is is38 diverter valve failure – boost leak under pressure (golf r mk7/7.5) serious on a Volkswagen Golf?

We rate it major and common on the Volkswagen Golf. The IS38 turbocharger fitted to the Golf R Mk7/7.5 uses a recirculation diverter valve (DV) that is known to fail under the higher boost pressures of the IS38 compared to the IS20. The internal membrane/piston degrades and allows boost to escape, causing a characteristic flutter or hissing sound and measurable power loss. Failure rate is accelerated on cars running a Stage 1 tune due to elevated boost. Widely documented across Golf R forums and confirmed by aftermarket manufacturers.

How much does it cost to fix on a Volkswagen Golf?

$180 to $480 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 Volkswagen Golf years are affected?

Our research records this fault on the 2014–2020 Volkswagen Golf. 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 IS38 diverter valve for external cracks or deformation. Apply vacuum and hold to test the valve membrane integrity. Scan for P0299 or boost-related codes. Listen for boost flutter on hard acceleration from 2,500 rpm. Look here: IS38 turbocharger compressor housing, passenger side of engine bay