International & Navistar Block Heaters: DT466, T444E, MaxxForce
The DT466 is one of the most-searched heavy-duty engines for block heaters, and for good reason: it lived in school buses, dump trucks, and medium-duty IH chassis across four decades, most of which park outside. The heater changed with each generation, so the year matters more than the displacement badge.
International's V8s — the 6.9L and 7.3L IDI and the T444E that became Ford's PowerStroke — are covered here too. All part numbers are Zerostart / Phillips & Temro with Kat's equivalents where both catalogs list the application.
Heater part numbers by application
Part numbers from the Zerostart / Phillips & Temro heavy-duty application guide, with Kat's equivalents where both catalogs list the engine. Numbers are occasionally superseded — confirm against a current catalog or dealer before ordering.
DT466 High Torque, DT466, DT466E, HT 530, DT530 (2001–2003)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500054 | 1,250 W | 120 V | 1-1/4" | Immersion | 3600008 |
Left side, in the protruding boss above the engine oil dipstick. Element direction 12 o'clock.
DT466 & DT570 (2004–2006); DT408, DT466, DT466E, 530, 570 (1994–2000)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500044 | 1,250 W | 120 V | 1-1/4" | Freeze plug | 3600008 |
| 8608911 | 1,250 W | 240 V | 1-1/4" | Freeze plug | 8608377 |
Replaces the 1-1/4" freeze plug in the boss on the left side of the engine.
MaxxForce DT, MaxxForce 9 & 10 (2007 and newer)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500098 | 1,250 W | 120 V | 1-1/4" | Freeze plug | 3600008 |
Replaces the 1-1/4" freeze plug in the boss on the left side of the engine.
D312, D414, DT414, D436, DT436, DTA466 (pre-1994)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8608512 | 1,250 W | 120 V | 1-1/4" | Freeze plug | 3600008 |
| 8608539 | 1,250 W | 240 V | 1-1/4" | Freeze plug | 8608377 |
Replaces the 3rd or 4th freeze plug on the left side of the engine.
DT360, DTA360
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8608601 | 1,000 W | 120 V | 1-1/4" | Freeze plug | 3600008 |
Replaces the 3rd or 4th freeze plug on the left side of the engine.
T444E 7.3L V8 (1994 and later)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500043 | 1,000 W | 120 V | 3/4" NPT | Immersion | 3600008 |
| 8600996 | 1,000 W | 240 V | 3/4" NPT | Immersion | 8608377 |
Replaces the 3/4" threaded plug in the oil cooler.
Kat's equivalents: 30307 (120 V) / 31307 (240 V).
6.9L (421 CID) & 7.3L (445 CID) IDI — not T444E
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3100043 | 1,000 W | 120 V | 1-1/2" | Freeze plug | 3600010 |
Replaces the freeze plug on the right rear of the engine, element at 11 o'clock. O-ring and clamp service kit: 3500005.
Kat's equivalent: 30403 (1,000 W).
Identifying your DT466 generation
Three questions pin down the right heater: Is it mechanical or electronic (DT466E, 1995+)? What model year — pre-1994, 1994–2000, 2001–2003, 2004–2006, or MaxxForce-era 2007+? And is there already a heater in the boss on the left side of the block, above the dipstick? Many buses and municipal trucks were ordered with one from the factory, and a dead element can be swapped for the same part number without touching the coolant beyond a partial drain.
The 1-1/4" freeze-plug heaters used across most DT generations seat with an O-ring and clamp rather than a press fit, which makes them one of the friendlier freeze-plug installs — no punching plugs into the block. Drain below the boss, pull the old plug or element, seat the new one square, torque the clamp, refill and check for weeps at operating temperature.
FAQ
Where is the block heater on a DT466?
On the left side of the block, in the boss above the oil dipstick. 1994–2006 engines use a 1,250 W 1-1/4" freeze-plug heater (Zerostart 3500044); 2001–2003 High Torque engines use the threaded 3500054; 2007+ MaxxForce DT uses 3500098.
What block heater fits a 7.3L International?
Depends which 7.3: the 1994+ T444E (the PowerStroke's twin) takes a 1,000 W 3/4" NPT immersion heater in the oil cooler — Zerostart 3500043 or Kat's 30307. The older 6.9/7.3 IDI takes the 1,000 W freeze-plug heater 3100043 (Kat's 30403) in the right rear of the block.
How many watts does a school bus block heater need?
DT466-powered buses use 1,250 W factory-style heaters, and that's the right size — enough to keep the 7.6-litre block startable at -40 with an overnight plug-in, and standard on most cold-climate bus fleets.
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