CriticalCommonEngine

Nissan Skyline: Turbo Oil Drain Line Coking — Bearing Starvation

Turbo Oil Drain Line Coking — Bearing Starvation is a common engine fault on the Nissan Skyline on the 1993–2002 cars, and we rate it critical. Putting it right costs $1,600 to $5,500 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 41 documented faults on the Nissan Skyline.

Vehicle: Nissan Skyline
Engine: 2.5L / 2.6L
Years: 1993–2002
Fuel: petrol
System: Engine

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

All Nissan Skyline faults41 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

On RB25DET and RB26DETT applications the turbocharger oil drain line routes from the turbo centre section back to the block via a steel tube with rubber connecting sections. When the engine is shut down hot, residual heat soaks the oil sitting static inside the drain tube; over thousands of heat cycles the oil carbonises and deposits build up (known as coking), progressively restricting the drain bore. A restricted drain causes oil to back up in the centre-section bearing housing, raises shaft seal pressure, forces oil past the compressor and turbine seals (blue smoke on overrun), and ultimately starves the floating bearings on cold start when the oil pressure supply exceeds the impeded drain. Bearing failure from oil starvation on shutdown is the terminal outcome and can destroy the turbo shaft into the compressor wheel.

What you would notice

Blue or grey smoke from exhaust on overrun or at idle
Oil residue around turbo compressor outlet or intercooler piping
Audible turbo bearing whine or grinding at high rpm
Elevated oil consumption with no visible external leak
Oil mist inside intercooler end tanks

How to check it

Where to look. Turbocharger centre-section oil drain line running from underside of turbo housing to engine block return port

Check the interior of the compressor housing for oil coating. Inspect the oil feed banjo bolt and screen for carbon contamination. On twin-turbo R34 GT-R check both primary and secondary turbo drain lines independently. If a workshop inspection is possible: Remove the turbo oil drain line and inspect visually for carbon deposits restricting the bore; a wire probe should pass freely if clean.

Parts involved: Turbocharger.

What it costs to put right

$1,600 to $5,500 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

“Have the turbo oil drain lines ever been replaced or flushed?”
“Is there any smoke from the exhaust on overrun?”
“Does the owner use a turbo timer or idle-down procedure before shutdown?”
“Has the turbo been rebuilt or replaced, and what was the cause?”

Now check the Nissan Skyline 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.

Nissan Skyline buyer questions

Is turbo oil drain line coking — bearing starvation serious on a Nissan Skyline?

We rate it critical and common on the Nissan Skyline. On RB25DET and RB26DETT applications the turbocharger oil drain line routes from the turbo centre section back to the block via a steel tube with rubber connecting sections. When the engine is shut down hot, residual heat soaks the oil sitting static inside the drain tube; over thousands of heat cycles the oil carbonises and deposits build up (known as coking), progressively restricting the drain bore. A restricted drain causes oil to back up in the centre-section bearing housing, raises shaft seal pressure, forces oil past the compressor and turbine seals (blue smoke on overrun), and ultimately starves the floating bearings on cold start when the oil pressure supply exceeds the impeded drain. Bearing failure from oil starvation on shutdown is the terminal outcome and can destroy the turbo shaft into the compressor wheel.

How much does it cost to fix on a Nissan Skyline?

$1,600 to $5,500 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 Nissan Skyline years are affected?

Our research records this fault on the 1993–2002 Nissan Skyline. 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.