Volvo D12 Turbocharger Guide: Holset HX52, HX55 & Garrett GT4594 by Engine Version

This Volvo D12 turbocharger guide starts with the question most owners actually have: which turbo is on my engine? The D12 was built for more than a decade in several versions, and Volvo fitted different turbochargers to them, from Holset and from Garrett. Order by the engine version on the data plate and the number on the turbo’s tag, never by “D12” alone. Below is what fits what, how these turbos fail, and what a replacement or rebuild costs.

Which Turbo Is on a Volvo D12

The Volvo D12 is a 12.1-liter inline six that powered VN, VNL, VNM and VHD trucks in North America and the FH12 and FM12 elsewhere, with ratings from about 345 to 465 horsepower in North American trucks (up to 500 in Europe). These are the turbochargers PT Turbo lists for it, with the engine version each is listed for.

Engine version	Turbo	Part numbers
D12A, 420 hp (also FH12, FL12)	Holset HX55	4049337H
D12C	Holset HX55	4031143H
D12C	Holset HX52	4031148H, 4031147H
D12, 435-465 hp	Holset HX52	3786675H, 3786676H
D12C, 425-465 hp	Garrett GT4594 and GTA4594BN	712922-5006S, 712922-5019S
D12D, 440 and 480 hp	Holset HX55	4033139H, 4033576H
D12F	Holset HE531VE (variable geometry)	4031005H
D12M (Volvo Penta marine)	BorgWarner S500WG	56509880000

More numbers are listed on the Holset HX55, Holset HX52 and Garrett GT4594 model pages. If your number is not there, send us the tag numbers and we will cross it.

One name that gets attached to this engine by mistake is the BorgWarner K31. The K31 is a different turbo for MAN, Mercedes-Benz and Volvo Penta engines; our BorgWarner K31 guide covers it.

Fixed Geometry or Variable Geometry

Most D12 turbos are fixed geometry. The HX55, HX52 and GT4594 have no moving vanes: exhaust drives the turbine, the compressor feeds the charge air cooler, and that is the whole mechanism. Versions with a W in the name add a wastegate.

The exception in the table is the Holset HE531VE on the D12F. Holset variable geometry turbos use a sliding nozzle driven by an electronic actuator, which gives fast boost at low speed and engine braking, and adds two things to maintain: the nozzle, which soot can bind, and the actuator. For how that hardware behaves, see our Volvo D13 turbocharger guide. For the operating principle, the variable-geometry turbocharger overview is a good primer.

Symptoms of a Failing D12 Turbocharger

Symptom	Likely cause	Check first
Low power, slow boost build, black smoke under load	Boost leak, restricted air filter, worn turbo	Charge air cooler and piping for leaks
Blue or gray smoke, oil in the charge piping	Worn bearings and seals, or a restricted oil drain	Shaft play and the drain line
Whine, siren or grinding noise	Bearing wear, wheel contact with the housing	Compressor wheel for rub marks
Oil at the compressor outlet with good shaft play	Crankcase pressure or a blocked air filter pulling oil past the seal	Air filter restriction and crankcase breather

Check shaft play by hand before you order anything, and pressure-test the charge air system. A turbo that is not building boost is often a leaking boot or cooler, not a failed turbo.

Replacement and Rebuild Options

Option	Price	Notes
New Holset HX55 for the D12	$849 to $1,992 (6 listings) at PT Turbo	Match the part number to the engine version
New Holset HX52 for the D12	$1,386 to $1,643 (4 listings) at PT Turbo	D12C and the 435-465 hp ratings
New Garrett GT4594 for the D12C	$1,390 to $1,531 (4 listings) at PT Turbo	425-465 hp ratings
Rebuild your own turbo	From $575 at PT Turbo (price list)	For a unit with sound housings and wheels

Price ranges in this article are general estimates to help with budgeting, not PT Turbo quotes. Our current prices are on each product listing, and our rebuild prices are on the turbo rebuild price list.

Our turbocharger rebuild service is a mail-in service. We inspect the turbo and confirm the price before any work starts, VSR balance every rebuild, and back it with a 12-month unlimited-mileage warranty; turnaround is 3 to 5 business days after inspection. PT Turbo has been in the turbocharger business since 1978 and stocks both new and remanufactured turbochargers.

Installation Tips for the D12

• Find out why the old turbo failed. Oil starvation, a restricted drain, debris and overspeed each leave their own marks. Fit a new turbo without fixing the cause and it fails the same way.
• Replace or clean the oil feed and drain lines. On a high-mileage engine a new feed line is cheap insurance.
• Change the oil and filter and prime the turbo with clean oil before the first start.
• Clean the charge air cooler. If the old turbo passed oil or shed metal, the cooler is holding it.
• Use new gaskets and check the exhaust manifold for cracks and warped flanges.
• Idle the engine for a minute before loading it so oil reaches the bearings.

Running other iron in your fleet? Our full list of turbo guides covers the Volvo D11 and D13, the Cummins ISM and ISX, the Detroit Series 60 and more.

Frequently Asked Questions

What turbocharger does the Volvo D12 use?

It depends on the engine version. PT Turbo lists the Holset HX55 for the D12A, D12C and D12D, the Holset HX52 for the D12C and the 435-465 hp ratings, the Garrett GT4594 for D12C ratings of 425 to 465 hp, and the Holset HE531VE variable geometry turbo for the D12F. Match the number on your turbo’s tag.

Is the BorgWarner K31 the Volvo D12 turbo?

No. The K31 is a BorgWarner turbo for MAN, Mercedes-Benz and Volvo Penta engines. The D12 truck engines use Holset HX52 and HX55 and Garrett GT4594 turbos.

Can a Volvo D12 turbo be rebuilt?

Yes, when the housings and wheels are sound. A rebuild renews the bearings and seals and balances the rotating assembly. Rebuild prices are on PT Turbo’s price list, and the price is confirmed after inspection, before any work starts.

Further reading: Learn more about turbocharger technology.