Detroit Diesel Block Heaters: DD15, Series 60 & the Two-Strokes
Detroit's four-stroke era (Series 60, Series 50, DD15) takes threaded immersion heaters in or near the oil cooler, just like its competitors. The legendary two-strokes — 53, 71 and 92 series — instead use bolt-on plate heaters that replace a water jacket access plate on the block, with the correct part depending on what accessories crowd that plate.
Every heater below sits directly in the coolant. Wattages run 1,000–1,500 W for the big engines, which is the right size to hold a full-size block 20–30°C above ambient through a Prairie night.
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 Numbers are occasionally superseded — confirm against a current catalog or dealer before ordering.
DD15 14.8L (2008 and newer)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500095 | 1,500 W | 120 V | 27 mm | Immersion | 3600008 |
Right side of the engine — threads into the M27 port in the oil module below the intake.
Series 60 (2007 and newer)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500077 | 1,500 W | 120 V | 1-3/16" STOR | Immersion | 3600008 |
Upper hex port of the oil cooler, right side of the engine.
Series 60 11.1L & 12.7L (pre-2007)
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8605556 | 1,500 W | 120 V | 1" NPT | Immersion | 3600008 |
| 8600260 | 1,500 W | 240 V | 1" NPT | Immersion | 8608377 |
Pre-1991: replaces the 1" NPT plug in the water pump outlet casting, right front. 1991+: replaces the 1" pipe plug near the top front of the oil cooler.
Series 50
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8600090 | 1,000 W | 120 V | 1" NPT | Immersion | 3600008 |
| 8605556 | 1,500 W | 120 V | 1" NPT | Immersion | 3600008 |
| 3500007 | 1,000 W | 120 V | 1-1/2" | Freeze plug | 3600008 |
NPT heaters replace the 1" plug in the oil cooler casting (except low-mount turbo engines). The 1-1/2" freeze-plug heater 3500007 installs in the core plug behind the oil cooler and covers low-mount-turbo engines too.
Series 55
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 3500008 | 1,500 W | 120 V | Plate | Immersion | 3600008 |
| 3500009 | 1,500 W | 240 V | Plate | Immersion | 8608377 |
Replaces the water jacket access plate on the left side of the engine.
Series 40 6.7L/7.6L/8.7L (after August 1993)
| 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" plug in the boss on the left side of the engine. Pre-September 1993 engines use 8608512 (120 V) / 8608539 (240 V) in the 3rd or 4th freeze plug instead.
8.2L (501 CID)
| 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" pipe plug on the right front side of the engine.
Two-strokes: 3-53, 4-53, 3-71, 4-71
Do not use a 1,000 W heater on 3-53, 4-53 or 3-71 engines.
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8600295 | 750 W | 120 V | Plate | Immersion | 3600008 |
| 8600368 | 1,000 W | 120 V | Plate | Immersion | 3600008 |
Replaces the water jacket access plate on the side of the engine.
Kat's equivalents: 30305 (750 W) / 30301 (1,000 W). Engines with a water-cooled compressor use 8601291/8601305 (Kat's 30308/30309) instead.
Two-strokes: 6-71
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8600368 | 1,000 W | 120 V | Plate | Immersion | 3600008 |
| 8600422 | 1,500 W | 120 V | Plate | Immersion | 3600008 |
Replaces the water jacket access plate. With a water-cooled compressor: 8601305 (1,000 W) / 8601372 (1,500 W).
V-71 & V-92 families: 6V/8V/12V/16V-71, 6V/8V/12V/16V-92, Silver Series
| Part no. | Watts | Volts | Size | Type | Repl. cord |
|---|---|---|---|---|---|
| 8601631 | 1,000 W | 120 V | Plate | Immersion | 3600008 |
| 8601704 | 1,500 W | 120 V | Plate | Immersion | 3600008 |
Replaces the water jacket access plate on the left front cylinder bank. 6V-71/8V-71 without power steering or A/C can instead take the 1" NPT heaters 8600090/8605556 in the front face of the left bank.
Kat's equivalents: 30314 (1,000 W) / 30315 (1,500 W). If an A/C compressor sits next to the access plate, the parts change — Kat's 30316/30304/31304.
Two-stroke plate heaters: check your accessories first
On the 53/71/92 two-strokes the correct heater depends on what's bolted next to the water jacket access plate. A water-cooled air compressor or an A/C compressor changes the plate clearance, and Phillips & Temro lists a different heater for each combination — that's why the tables above carry the qualifier. Before ordering, look at the side of your block and note what's mounted beside the plate.
The plate swap itself is straightforward: drain the coolant below the plate, unbolt it, clean the surface, and torque the heater plate on with a new gasket. Service parts (hex nuts, element gaskets, plate gaskets) are available separately, so a leaking 40-year-old install can usually be resealed without replacing the element.
FAQ
Where is the block heater on a Detroit Series 60?
2007+ engines: the upper hex port of the oil cooler on the right side — Zerostart 3500077 (1,500 W). Pre-2007 11.1L and 12.7L engines take 8605556 (1,500 W, 1" NPT) near the top front of the oil cooler; pre-1991 engines put it in the water pump outlet casting.
What block heater fits a DD15?
Zerostart 3500095 — a 1,500 W immersion element that threads into the M27 port in the oil module, below the intake on the right side of the engine.
Do Detroit two-strokes take a normal block heater?
They use bolt-on plate heaters that replace the water jacket access plate rather than a threaded or freeze-plug element. The exact part depends on the engine (53/71/92 series) and whether a water-cooled compressor or A/C compressor is mounted beside the plate — check the tables above.
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