6.0L Power Stroke Cooling System Service Guide

6.0L Power Stroke Cooling System Service and Coolant Flush Procedures

Cooling system service is particularly important on 6.0L Power Stroke diesels to avoid sludging and build up that risks clogging the minute passages found in the engine oil cooler assembly. The factory Motorcraft Gold engine coolant, which has a relatively high concentration of silicates, is frequently blamed for problems associated with oil and EGR cooler failures. As a result we'll be providing information on far superior Extended Life Coolants and performing our own ELC conversion on the shop's 6.0L Power Stroke.

6.0L Power Stroke Coolant Selection

Performing a cooling system flush without special equipment is not a daunting task, but expect the process to take the better part of a day since you'll have to drain, flush, drive several times in order to completely flush the system. Cooling system service is particularly important on the 6.0L Power Stroke as complications with oil cooler clogging begins with coolant breakdown and the resulting buildup of silicate gels in the cooling system. Ford recommends that the engine coolant be changed every 45,000 miles/3 years after performing the initial 100,000 mile/5 year service.

Concentrated engine coolant is typically mixed in a 50/50 ratio with distilled water. Some will advise that tap water is perfectly acceptable, however distilled water is ideal as it contains no minerals and there are therefore [theoretically] no concernable particulates or chemicals in the water. The minerals in tap water can have a tendency to contribute to scale build inside a cooling system.

Water actually has favorable heat transfer characteristics over anti-freeze, while pure anti-freeze provides the greatest protection against freezing and corrosion. Too much water results in corrosion/scale buildup and increases the freezing temperature, while a concentration with too much anti-freeze thickens the engine coolant and has a tendency to cause premature water pump failures. A 50/50 mixture therefore plays on the advantages of both water and anti-freeze. In extremely cold conditions, up to a 60/40 mixture (60% anti-freeze, 40% water) is acceptable in 6.0L Power Stroke diesels to bring the engine coolant freezing temperature down further.

Motorcraft Gold Engine Coolant in 6.0L Power Stroke Diesels

Engine coolant/anti-freeze comes in many chemical compositions and formulations. From the factory, all 6.0L Power Strokes were filled with Motorcraft Gold engine coolant. Motorcraft Gold contains silicates; various compounds formed from silicon and oxygen atoms. Under intense heat, thermal breakdown takes its course and the silicates are forced out of suspension from the rest of the mixture, collect, and ultimately contribute to oil cooler clogging. Oil cooler clogging is a common problem with the 6.0L Power Stroke and Ford's Motorcraft Gold engine coolant have been identified as a probable (likely) cause. As a result, it is not uncommon for owners and/or shops to convert to a silicate free or low silicate extended life coolant (ELC). If continuing to use Motorcraft Gold engine coolant, it is extremely important that you follow Ford's 45,000 mile flush interval.

Extended Life Coolant (ELC)

Extended life coolants, or ELCs are engine coolants designed to require less frequent service by providing superior resilience against thermal breakdown. ELCs are commonly found in class 7 and 8 tractors and exhibit service intervals in the 300,000+ mile range. In the following procedures, we completely flush the cooling system using Fleetguard Restore (beneficial silicate removal properties) and replace the OEM Motorcraft Gold formulation with a silicate free Fleetguard engine coolant. The standard service life of our Fleetguard fluid is 300,000 miles; a huge improvement over Ford's 45,000 mile interval. Other notable ELCs on the market include Shell Rotella ELC, Shell Rotella Ultra ELC, Fleetrite ELC (International's service brand), and various coolants from Fleetguard (Cummins' service brand). Avoid common "budget brands" and universal anti-freezes; your engine deserves better.

Engine coolant types are not cross-compatible; do not mix different engine coolant brands, colors, product lines, etc. If you are converting to a new engine coolant, a flushing or cleaning compound should be used to remove trace elements of the old coolant. Ideally, select a flushing compound (such as Fleetguard Restore) that is specifically designed to breakdown and remove silicate gels.

6.0L Power Stroke Cooling System Service Part Numbers


Part Number



Motorcraft RT-1169
(Ford 3C3Z-8575-AA)

Includes o-ring seal. Replace during service; do not reuse

Degas bottle/tank cap

Motorcraft RS-527

Replace during service; do not reuse

Degas bottle/tank hose

2003 - 2004

Motorcraft KM-4848
(Ford 5C3Z-8075-CA)

Large hose attached at bottom of degas tank; replace during service

2005 - 2007

Motorcraft KM-4858
(Ford 5C3Z-8075-CB)

Degas bottle/tank

Ford 6C3Z-8A080-B

Replace as necessary if tank is damaged, full of sludge, etc; replace if changing coolant type

Upper radiator hose

Motorcraft KM-4595

Replace during service; do not reuse

Lower radiator hose

2003 - 2004

Motorcraft KM-4784
(Ford 3C3Z-8286-AJ)

Replace during service; do not reuse

2005 - 2007

Motorcraft KM-4923 (4x2)
Motorcraft KM-4877 (4x4)

Coolant flush solution

Motorcraft VC-1

Recommended by Ford Motor Company

OEM engine coolant

Motorcraft VC-7-B

1 gallon container, Motorcraft Gold concentrated engine coolant

6.0L Power Stroke Coolant Flush and Cooling System Service Procedures

Some quick notes about the following cooling system flush procedures:

• There are many ways to perform a DIY coolant flush; this is simply our method.
• This technique requires no special equipment but typically uses 25 to 30 gallons of distilled water. For the earlier flush cycles, tap water can be substituted but the "right" way is to use distilled water. Plus, you'll be able to use the plastic jugs to store and recycle your used coolant.
• These procedures require that you use a concentrated engine coolant; this flush technique will NOT work with a premixed solution.

Click any thumbnail to view high resolution fullsize image w/ addition details (where applicable)

6.0L Power Stroke radiator drain valve location

• Locate the drain valve/petcock on the bottom of the driver side of the radiator. The petcock on the factory radiator uses an 8 mm hex key (Allen head). For convenience, you may want to attach a section of 5/16" heater hose or fuel line to the petcock. This reduces splash-back if emptying into a shallow container or can be used in place of a funnel if draining the radiator into 1 gallon containers.

• Remove the degas bottle cap (radiator overflow) and drain the radiator into a suitable container. Note that with each radiator drain, you'll only remove roughly half of the total engine cooling system capacity (~3.5 gallons). Removing the lower radiator hose at the radiator connection drains a few extra quarts.

• Close the petcock and fill the cooling system with water (tap water is an acceptable substitute for distilled water at this stage) through the degas bottle. Once the water level reaches the "MAX" fill indicator on the degas bottle, replace the cap and start the engine.

• Allow the engine to reach operating temperature by taking the truck for a short drive, then park the truck and allow the engine to cool. During this and all subsequent flush cycles, the defroster should be turned on in order to maximize coolant flow through the heater core.


6.0L Power Stroke degas bottle

• Drain the radiator once more, then add the appropriate amount of flush/cleaning solution and fill the remainder of the cooling system with water (tap water is an acceptable substitute for distilled water at this stage). Next, follow the directions as outlined by the cooling system flush manufacturer. We use and highly recommend Fleetguard Restore, which requires that the engine be run at operating temperature for 60 to 90 minutes (frequent short drives keep the operating temperature up, as it will drop quickly if left to idle).

• Park the truck and allow the engine to cool, then drain the radiator once again. Refill the cooling system with distilled water (tap water is not recommended as a substitute for distilled water beyond this point), start the engine, and allow the truck to run at operating temperature for a minimum of 10 minutes.

• Repeat the drain, refill, run engine at operating temperature cycle a minimum of 5 times. If after 5 flushes the cooling system drains clear, continue to the next step. If the cooling system drains with any color at all, continue to flush the system until only a clear liquid drains. The goal is to have a cooling system that contains only distilled water. Note - warm water may appear cloudy when drained, this is normal.

6.0L Power Stroke thermostat location

• Drain the radiator once more, then replace the thermostat, degas bottle cap, degas bottle hose, upper radiator hose, and lower radiator hose. You may also consider replacing the entire degas bottle, depending on its condition (part numbers listed above). Start by removing the air filter assembly and cold side intercooler tube (intercooler to air horn tube).

6.0L Power Stroke fuel filter housing

• You'll also want to remove one fuel line from the fuel filter housing in order to better access the rear thermostat housing stud (see picture for specifics). With the fitting loosened completely, the fuel line can be gently pushed out of the way.

6.0L Power Stroke thermostat replacement

• For 2003 and early 2004 model year trucks, the exhaust backpressure sensor (EBPS) bracket is attached to the thermostat housing. The sensor and bracket must be removed to access the thermostat housing. With these items removed, the thermostat housing is held in place by (2) x bolts requiring a 1/2" socket. Be sure to install the new thermostat in the correct position and lightly coat the thermostat housing o-ring in clean engine oil before installing (wipe off any excess oil).



6.0L Power Stroke lower radiator hose and degas bottle hose

• Removal of the upper radiator, lower radiator, and degas bottle hoses is relatively straight forward. Once the hoses, thermostat, and degas bottle cap have been replaced, reinstall the intercooler tube and air filter assembly.

• The 6.0L Power Stroke has a 6.875 gallon cooling system capacity. At this point, whatever is left in the cooling system is, for all intents and purposes, pure distilled water and you should have removed 3.5+ gallons from the cooling system during the last drain (if you didn't replace it, remember to drop the lower radiator hose to drain those few extra quarts!).

• Add approximately 3.4 gallons of engine coolant concentrate to the cooling system through the degas bottle, then add distilled water until the coolant level reaches the indicator on the degas bottle. Bring the engine to operating temperature, then allow it to cool and check the coolant level. If the level is low, add distilled water; do not add anymore coolant concentrate.