The BorgWarner K27 Turbocharger is one of the most widely used medium-frame turbos in the European diesel world, powering everything from Mercedes-Benz commercial trucks to Deutz industrial engines and marine applications. If you run Mercedes OM-series diesels or wrench on European heavy equipment, chances are you have seen a K27 hanging off an exhaust manifold at some point. This guide covers real applications, specs, failure symptoms, and replacement options so you can spec the right unit the first time.
At PT Turbo we have been rebuilding and supplying turbochargers since 1978. That is 45+ years of hands-on experience with the KKK/BorgWarner K-series, and we stock both new and remanufactured units along with the actuators and hardware that fail alongside them.
What Is the BorgWarner K27 Turbocharger?
The K27 comes from the original Kühnle, Kopp & Kausch (KKK) turbo line, which BorgWarner absorbed and continues to build today. It sits in the middle of the K-series lineup, larger than the K24 and K26, smaller than the K29 and K31.
The “27” refers to the frame size, roughly indicating the compressor and turbine wheel dimensions. That mid-frame sizing is exactly why it fits so many 5 to 12 liter diesel engines making somewhere between 150 and 400 horsepower.
You will find the K27 in both wastegated and fixed-geometry forms, plus later VTG (variable turbine geometry) variants on emissions-era Mercedes engines. If you want a primer on how these systems work, variable-geometry turbocharger technology is worth a quick read before you spec a replacement.
K27 General Specifications
| Attribute | Typical K27 Range |
|---|---|
| Frame size | 27 (mid-frame) |
| Compressor wheel | ~60-68 mm inducer |
| Turbine wheel | ~62-70 mm exducer |
| Engine displacement | 5.0L to 12.0L diesel |
| Power range | 150-400 hp |
| Bearing system | Journal bearing, water/oil cooled |
| Configurations | Fixed, wastegated, VTG |
Mercedes & European Diesel Applications
The K27 earned its reputation on Mercedes-Benz OM-series engines. These are the workhorse diesels found in Atego, Axor, and Unimog trucks, as well as older OM366 and OM906 platforms used in buses, agricultural equipment, and generator sets.
Beyond Mercedes, the same K27 frame shows up across the European industrial landscape. Deutz, MAN, MTU, and various marine builders all specced K-series turbos for their reliability under continuous load.
- Mercedes-Benz OM366 / OM366LA — 6.0L inline-six, trucks and buses
- Mercedes-Benz OM906 / OM926 — 6.4L and 7.2L, Atego and Axor
- Deutz BF6M / BF4M series — industrial and ag applications
- MAN D-series — select mid-range displacements
- Marine & genset — continuous-duty power units
Because so many variants exist, the casting number stamped on the compressor housing and center cartridge is the only way to confirm a match. Never order a K27 off engine model alone. Two trucks with the same OM906 can carry different A/R housings depending on rating and emissions year.
Common BorgWarner K27 Turbocharger Failure Symptoms
A K27 rarely dies without warning. Catching the early signs saves you from a spun bearing that sends metal downstream into the intercooler and intake tract.
Most failures trace back to three causes: oil supply problems, actuator or wastegate faults, and foreign object damage. On VTG units, sticking vanes from soot buildup are the number one complaint.
| Symptom | Likely Cause | Severity |
|---|---|---|
| Blue/gray exhaust smoke | Failed seals, oil in exhaust | Moderate |
| Whining or grinding noise | Worn journal bearings | High |
| Low boost / power loss | Stuck actuator or vanes | Moderate |
| Excessive shaft play | Bearing wear | High |
| Boost overshoot / limp mode | Wastegate/actuator fault | High |
| Oil leaking from CHRA | Clogged drain or seal failure | Moderate |
If you catch shaft play or a grinding noise, shut it down. Running a turbo with failed bearings for even a short time can grenade the wheels and contaminate the entire charge-air system.
Actuators: The Part That Fails Before the Turbo
On wastegated and VTG K27 units, the pneumatic actuator is usually the first thing to go. A weak or stuck actuator throws boost codes, causes limp mode, and gets misdiagnosed as a bad turbo more often than any other component.
Before you condemn a good cartridge, test the actuator. Many of the K27’s European cousins share Garrett and Mitsubishi actuator designs, so we stock a range of direct replacements.
- Garrett pneumatic actuator 757979-5102, a common heavy-duty replacement, available from PT Turbo for $240.94. View the Garrett Pneumatic Actuator 757979-5102 here.
- Mitsubishi TD03 pneumatic actuator 49S3118761, a budget-friendly option for smaller frames at $104.33. View the Mitsubishi TD03 Actuator 49S3118761 here.
- Mitsubishi pneumatic actuator 4918918935, the lowest-cost actuator we stock at $83.99. View the Mitsubishi Pneumatic Actuator 4918918935 here.
- Garrett pneumatic actuator 445963-0040, a premium VNT-style unit for higher-boost applications at $465.52. View the Garrett Pneumatic Actuator 445963-0040 here.
Replacing a failed actuator instead of the whole turbo can save you well over a thousand dollars when the cartridge is still healthy. Not sure which one fits your application? Contact PT Turbo with your casting number and we will match it.
New vs Remanufactured K27: Cost Breakdown
A brand-new OEM BorgWarner K27 from a dealer often runs well past what most owner-operators want to spend, and lead times on European part numbers can stretch for weeks. A quality remanufactured unit is the smart middle ground for most fleets.
Our remanufactured turbochargers are built to OEM balance specs with new bearings, seals, and wheels where needed. Every unit is VSR balanced and tested before it ships.
| Option | Typical Cost | Lead Time | Best For |
|---|---|---|---|
| New OEM K27 | $1,800-$3,000+ | 1-4 weeks | Warranty-critical fleets |
| Remanufactured K27 | $700-$1,400 | In stock / fast | Most owner-operators |
| Rebuild your core | $450-$900 | 2-5 days | Cost-conscious, no core hunt |
If you have a good core, our turbocharger rebuild service is the most economical route. We keep your original housings and casting numbers, which guarantees fitment on hard-to-source European units.
Installation & Longevity Tips
The K27’s biggest enemy is oil. These are journal-bearing turbos, and they live and die by clean, pressurized lubrication reaching the center housing within seconds of startup.
Follow these steps and a rebuilt K27 will outlast the job that killed the last one:
- Prime the oil feed before first start. Crank with the fuel off until you see pressure.
- Replace the oil feed and drain lines. Coked or restricted lines are the top cause of repeat failures.
- Clean the intake and intercooler if the old turbo shed any metal or oil.
- Check crankcase ventilation. High crankcase pressure pushes oil past the drain and out the seals.
- Let it idle down before shutdown. Thirty seconds of idle prevents oil coking in the bearing.
On VTG variants, keep up with regen cycles. Excess soot from a faulty EGR system jams the variable vanes and
Cross-Reference & Superseded Part Numbers
The turbochargers covered in this article match or supersede the following OEM and manufacturer part numbers. If you are searching by part number, these are the units stocked by PT Turbo for this application:
172-784-0004 • 172-784-0090 • 172-784-0130 • 172-784-0578 • 479514-RMN • 53047109901-BILLET • 53047109904-BILLET • 53249886705 • 53279880004 • 53279880007 • 53279880012 • 53279880014 • 53279880020 • 53279880022 • 53279886206 • 53279886425 • 53279886441 • 53279886444 • 53279886507 • 53279886533 • 53279886534 • 53279887101 • 53279887115 • 53279887118 • 53279887120 • 53279887160 • 53279887161 • 53279887163 • 53279887192 • 53279887196 • 53279887206 • 53279887208 • 53279887210 • 53319886911 • 53319887137 • 53319887147 • 53339886403 • 53339886429 • 53339887001 • 53369886703 • 54399880049 • 56409880017 • 56419880001 • 56419880016 • 57509900000 • 709838-5006S • 709838-9006S • 729546-5002S • 736088-5006S • 761154-5007S • 765155-5008S • 765155-9007W • 777318-5002W • 777318-5003W • 777318-9003W • 778794-5002S • 802774-5008S • 817280-5001S • 827052-5002S • 827053-5001S • 827054-5002S • 827056-5001S • 828375-0001 • 832808-0001 • 952201-5001S • A4720901480-RMN • F41CAY-S0091B • F41CAY-S0103B • F41CAY-SR057B • F41CAY-SR061B • F41CAY-SR073B • F41CAY-SR074B • F41CAY-SR075B • F41CAY-SR076B • F41CEY-SR082B • F43VAY-S0094B • JT12337 • JTC11010 • JTC11033 • JTC11039 • JTC11068 • JTC11191 • JTC11207 • JTC11305 • JTC11323 • JTC11369 • JTC11399 • JTC11403 • JTC11434 • JTC11478 • JTC11555 • JTC11597 • JTC11720 • JTC11781 • JTC11847 • JTC11849 • JTC11850 • JTC11851 • JTC11854 • JTC11949 • JTC12246 • NEW-FTR-TWN-TRB • RMN-BRG-V2S-TWN • RMN-BRG-V2S-TWN-GR-TO • RMN-BRG-V2S-TWN-NO • V30VEY-SR021B • V41VEY-SR020B • V41VEY-SR025B
Can’t find your number above? Contact PT Turbo — our team has been matching part numbers since 1978.
Need a Turbocharger?
PT Turbo has rebuilt and sold turbochargers since 1978. We stock remanufactured units for Cummins, Duramax, Power Stroke, Detroit Diesel, and more — backed by a 12-month unlimited mileage warranty and same-week shipping from San Bernardino, CA.
📞 (909) 824-1020 · 346 S I St. #3, San Bernardino, CA 92410 · [email protected]
