BorgWarner Turbo Repair and Rebuild, Sorted by Part Number Prefix

BorgWarner is the name of a turbocharger maker, not a type of turbocharger, and its families do not stay on one side of any line an owner might use to sort them. The same family name turns up on petrol and diesel engines, on three-cylinder hatchbacks and six-cylinder saloons, alone or as one half of a twin-turbo set. What does sort them is the BorgWarner number itself, starting with its first four digits.

Is Your Turbo a BorgWarner? Where the Name and Number Sit

BorgWarner’s own identification guidance puts the nameplate on the compressor housing, the intake side of the turbo, and lists three numbers on it: the part number given by the vehicle or engine manufacturer, a serial number unique to that one unit, and BorgWarner’s part number. BorgWarner calls the last of these the former 3K/Schwitzer part number and the most useful of the three for service. Our BorgWarner K03 and K04 page walks through that plate line by line.

If the maker’s name has burned off, the shape of the number still tells you whose it is:

• BorgWarner: four digits, three digits, four digits, as in 5439-970-0127, and often typed without the dashes as 54399700127. A two-stage set listed as one assembly uses the same shape with a 1000 prefix.
• Garrett: six digits, a dash and four more, as in 758352-0022.
• Mitsubishi (MHI): 49, three more digits, a dash and five digits, as in 49173-07508. Our Mitsubishi MHI turbo repair page covers those.

The vehicle maker’s number has a shape of its own. Volkswagen-group numbers on these turbos begin with codes such as 03G253 or 03L253, BMW’s begin 1165 when written in full, and Nissan’s begin 14411. None of them tells you the turbocharger’s family, which is why the BorgWarner number is the one to read first. Photograph the whole plate rather than copying one line from it.

BorgWarner Part Number Prefixes and the Families Behind Them

The table below sorts every BorgWarner prefix in the fitment data our rebuild listings are built from. It shows the family names catalogued under each prefix, examples of where those units are listed, and the page on this site that covers them in depth. It is a map of our data, not of BorgWarner’s whole range, and it is a route to the right page rather than a fitment guide.

Four digits narrow it; they do not always finish it

Most prefixes in the table carry a single family. Three do not. 5303 is shared by the K03, the BV43 and the BV45, three units with nothing in common but their maker. 5435 holds both KP35 and BV35 references, and 5439 both KP39 and BV39. So the prefix gives you a shortlist, and the engine or the family name printed with the number picks from it.

The middle group of three digits is the least reliable part of the number. The same turbocharger is often listed under more than one middle group, such as 970 and 988, so a quote whose middle digits differ from your label is not, on that evidence alone, a different unit. Our K03 and KP35 pages show examples of both.

K03 and K04: Known for VW-Group Petrols, Not Confined to Them

K03 references begin 5303 and K04 references 5304. Most owners meet them on VW-group petrol engines, the 1.8 T and later 2.0-litre units in the Audi A1, A3 and A4, and on the B5 S4 and RS4, which carry two K03s rather than one. Everything specific to those installations, from reading the plate to what a repair kit leaves out, is on our K03 and K04 turbo repair page.

The family does not stop at petrol engines. Our data catalogues a K03, 5303-970-0048, on the 1.9 dCi diesel in the Renault Trafic and Vauxhall Vivaro, set out on our Trafic and Vivaro turbo repair page. And the K04 turns up far more often on diesels than its reputation suggests, as one of the two stages in Mercedes-Benz, Vauxhall and Volkswagen twin-turbo sets, covered further down this page.

KP35, KP39 and BV39: The Small-Engine Family

References beginning 5435 and 5439 belong to BorgWarner’s smallest common units, and they reach further than any other family on this page. Our fitment data places them on engines from a three-cylinder 1.4 TDI to BMW’s 3.0-litre six, and on 1.4 TSI and 1.6 EcoBoost petrol engines as well as diesels. The closely related KP31, under 5431, is catalogued on the 75 bhp Corsa 1.3 CDTi.

This family has a page of its own, and it carries the detail this hub leaves out: why a 5435 can be a BV35, why one build was filed under two names, and the thrust flinger that decides how these units are rebuilt. Start there, then go to the engine:

• The family itself: BorgWarner KP35, KP39 and BV39 turbo repair
• 1.5 dCi: our Renault and Dacia 1.5 dCi and Nissan Qashqai 1.5 dCi pages
• Vauxhall 1.3 CDTi: our Corsa and Fiat 1.3 CDTi and Multijet page

BV38, BV40, BV43, B01 and B03: The Later Diesel Units

These are the BorgWarner units most likely to be on a diesel built from the late 2000s through the 2010s, and they are the ones a search for the maker’s name rarely shows. None has a page of its own here, because each is best read alongside the engine it sits on.

• BV43 (5303). Catalogued on the VW-group 2.0 TDI in the Audi A3, A4, A5, A6 and Q5 and the VW Golf. On the Golf the 2.0 TDI is listed with BorgWarner and Garrett units for some of the same engine codes, which our VW Golf TDI turbo repair page sorts out.
• BV40 (5440). Listed on the common-rail VW-group 2.0 TDI across Audi, SEAT, Skoda and Volkswagen models, on BMW’s N47 at its lower outputs and the B47 in the 1 Series, and on the SsangYong Rexton 2.0.
• BV38 (5438). Catalogued on the 1.5 dCi from 2011, on Vauxhall’s 1.6 CDTi in the Astra, Insignia, Mokka, Zafira and Meriva, and as the single turbo on the lower-output Trafic and Vivaro 1.6 dCi.
• BV45 (5303). Listed on the 140 kW Nissan Navara D40, and twice over on BMW’s three-turbo N57.
• B01 and B01V (1635), B03 and B03G (1850 and 1853). Catalogued on later 1.5 dCi engines in Renault, Dacia, Nissan and Mercedes-Benz models, on VW-group 1.6 and 2.0 TDI, and in pairs on the VW Transporter BiTDI and the 236 bhp VW 2.0 TDI.

Several of these units carry an electronic actuator rather than a vacuum can. On the Rexton 2.0 the BV40’s actuator is BorgWarner’s own, and on the Navara the BV45 is catalogued with an electronic actuator too. When the fault is in the actuator and not the turbo, that part is repaired on its own: our SsangYong and Navara D40 actuator pages explain how each is identified, and our guide to turbo actuator replacement costs compares that repair with replacing the actuator or the whole turbo.

BorgWarner Sets on Twin-Turbo Diesels

In our fitment data, BorgWarner two-stage sets are listed on diesels from five carmakers. Each set is two or more complete turbochargers built to work together, and the stages are drawn from the families above, which is why the K04 and the KP35 keep reappearing in diesel listings.

A set can be catalogued as the whole assembly under a 1000-970 number, as one stage of that number with (I) or (II) after it, or as each stage under its own 5304, 5435, 5439 or 1635 number. Our Sprinter and Vito page shows how those three forms fit together on the OM651, and it is worth reading before you compare any two quotes for a set.

What to send is simpler than the numbering. Tell us on the Repair Form that the engine is a twin-turbo before anything is removed, then send the assembly as it came off the engine. Each stage is identified and measured on the bench in its own right, so you are not asked to work out which one has failed.

Our BorgWarner Turbo Rebuild

You, or the garage working on the car, remove the turbocharger and post it to us; we rebuild it and send it back ready to refit. The same sequence applies to every family on this page:

1. Complete the online Repair Form with the registration, the power output from your V5C, the mileage, the symptoms and any fault codes. Add the full BorgWarner number, all three groups of digits, the vehicle maker’s number and a photograph of the plate if you can.
2. Remove, pack and post the unit complete, actuator attached and every port covered, to Unit 102 Reaver House, 12 East Street, Epsom, Surrey, KT17 1HX, United Kingdom. Our FAQs page covers packing and postage.
3. Identification. The number is read against the fitment data, or the unit is identified on the bench where the plate has gone, so a 5303 is confirmed as a K03, a BV43 or a BV45 before any part is chosen.
4. Strip and measure. The unit is stripped to component level, and the shaft, wheels, bearing surfaces and housings are cleaned and measured against the original specification.
5. Rebuild. Bearings, seals and thrust parts are renewed with genuine OE or OEM-grade components, uprated where the original has a known weakness, and a wheel, shaft or housing that fails inspection is replaced.
6. Boost control. On a wastegated unit the flap, spindle and bush are checked and renewed where worn; on a variable-vane unit the vane mechanism is cleaned, freed or renewed and its travel set. Which of the two a unit has is confirmed on the bench, not assumed from its family name.
7. Balance, test and return. The rotating assembly is balanced, the finished unit is bench-tested, and it is boxed and posted back.

Bench time is typically one to three working days from arrival, plus postage each way, and the rebuild carries a lifetime, unlimited-mileage warranty with no time limit. Independent garages and dealers send units in for their customers in exactly the same way owners do.

Rebuild or replace?

Rebuilding your own BorgWarner starts from £185 + VAT, and a replacement unit from us starts from £450 + VAT; your exact price is confirmed once the unit has been inspected. Our turbo repair price guide sets out the ranges. A rebuild is the sensible default when the housings, shaft and wheels pass inspection, because the unit that goes back on is already the right family, the right build and the right number for your engine. When too much has failed at once, we say so and recommend a replacement.

Whichever unit goes back on, find what wore out the old one first. Our guide to common turbocharger problems sorts the symptoms and the cheaper faults that imitate them, and our guide to replacing a turbocharger covers the checks to make while the unit is off and how to prime the oil feed before the first start.

BorgWarner Turbo Repair FAQ

Final Thoughts

A BorgWarner label tells you who made the turbocharger and very little else on its own. The families cross petrol and diesel, small engines and large ones, single turbos and twin-turbo sets, so the fastest route to the right advice is the first four digits of the BorgWarner number, then the engine, then the page that covers it.

Where the prefix is shared, as 5303, 5435 and 5439 are, the engine or the family name printed with the number settles it. Where a set is involved, send the assembly complete. And if the plate has gone, send the unit anyway, because the bench reads what the label no longer can.