The oil cooler system from a 1997 police interceptor

There were a handful of problems that had developed with this system due to old age (7 years old), high mileage (over 150k miles), and being operated in an enviroment where large quantities of chloride salts are used to clear the highways of snow and ice during the winter.

-Oil was slowly leaking around where the rubber hoses sealed to the adapter.
-The surfaces of the rubber hoses had numerous hairline cracks in them and looked ready to burst open in the near future.
-The oil cooler->radiator core support bracket had a considerable amount of surface rust on it. But this appeared to be more of a cosmetic issue rather than a structural one.
-One of the bolts that secured the oil cooler bracket to the radiator core support had the head rounded off it and could not be turned with a wrench.
-The aluminum casting of the oil cooler was corroded around where the 1/4" 8mm mounting bolt fastens the hoses to the air->coolant heat exchanger. This caused the head of the bolt to snap off when a ratchet was used in an unsuscessful attempt to remove the fastener. To be reused, the remnants of the broken fastener in the oil cooler would have to be drilled out, and then have threads tapped into it.
-The aluminum casting of the oil cooler was corroded around where the hoses slid into the cooler. And required prying the two items apart with a long flat blade screwdriver.
-One of the garter springs in the "quick release" "spring lock" that secures the hoses to the oil filter adapter snapped and the hose fell out of the adapter. Luckily, this happened after the oil cooler system had already been removed from the vehicle.

The entire system out of the car

This system transfers heat from the circulating oil into the circulating coolant without actually allowing the two fluids to touch. The coolant then flows through the radiator where heat is released into the atmosphere.

The oil filter system in the car

(Power steering pump and steering gear removed for added picture clarity. Majority of stray oil cleaned up using various solvents)

Engine bay viewed from the top with the cooling fans and shroud removed

Defective power steering pump that caused a thick layer of black sludge to be applied to the engine front cover and oil cooler system components. Also note that the hydraulic valving inside the steering gear was severly worn and the vehicle always wanted to make a "hard right turn". (Possibly caused by metallic debris from the failed pump contaminating the steering gear).

As mentioned previously, the oil cooler system had numerous problems and needed to be repaired before it failed catastrophically and caused the engine to "seize up" due to a lack of lubrication. And this vehicle is not used for towing a heavy loads (such as a pleasure boat) nor is it going to idle in the 120 degree heat of the southern california desert for extended periods. So the oil cooling system is going to be "decontented" and replaced with it's civilian counterpart.

The oil filter adapter for a civilian 1997 crown victoria.

A collection of parts to be installed onto the vehicle. Take note of the civilian lower radiator hose.

A couple closeup pictures of the gasket that sits in between the engine block and the oil filter adapter.

The old police interceptor oil filter adapter still mounted to the block

The oil filter adapter removed from the block

After removing the old gasket that was stuck to the block

A couple closeups of the corrosion that has formed around the top coolant passage

Removing the corrosion that has built up around the top of the coolant passange is necessary to get the new gasket and filter adapter to seat properly. Having coolant mix with oil would cause engine failure very quickly. Since removing the engine from the car and sticking the block on a milling machine would be extremely labor instensive and costly, lets try some abrasives first. Here are the results after cleaning up the area with a dremel and some 400 grit sandpaper.

And lets bolt the adpater onto to the engine block.

And install the oil pressure sender.

Note in the 2000 model year, the electrical connector portion of the sender was revised. On 1999 and prior vehicles, you may have to squeeze the harness electrical connector for the sender with a pair of pliers to make sure it doesn't "walk off" the sender. Also note that the sender is an on/off device. It electrically opens when pressure drops to around 5 PSI. The rest of the time, it provides a ground path through the metal oil filter adapter.

The reddish substance on the sender is a one use adhesive applied so that the sender doesn't start to spin out of the adapter or seep oil around the threads

Now screw on the oil filter. Make sure that the o-ring doesn't fall off in the process.

Previously, the vehicle had developed a coolant leak in the front coolant crossover of the intake manifold. And someone thought they could "fix" the problem by pouring a large quantity of some sort of "stop leak" into the coolant system. The end result was a vehicle that ran really hot due to a restricted radiator.

Anyone know what brand of stop leak leaves residue like this?

If oil pressure problems develop inside your crown victoria's engine, often the timing chain tensioners will get noisy because they are at the end of the oil path.

1992-1997 crown vic with coolant reservoir on rear passenger of passenger fender liner


-All 1992-2008 crown victorias police cruisers use a similarly designed oil cooler setup. Part way into the 2009 model year, a new oil cooler setup was introduced on police interceptors and these cars use a different oil filter adapter at the engine block and no longer have the long tube style heat exchanger located near the bottom center section of the radiator.
-1997 was the last year that the oil cooler hoses were retained to the adpater using "spring locks". In 1998 and later vehicles, the hoses are retained to the adapter using a pinch bolt
-Be careful not to snap the head off of the pinch bolts which retain the oil cooler lines to the heat exchanger or the filter adapter. The bolts are steel, the part they screw into is aluminum. Spraying penetrant oil onto these parts before attempting to remove the bolt can help lower the chances of snapping off the fastener heads and then having to drill/tap out the remnants of the broken bolt. It should be noted that if the oil cooler hoses have been leaking for a while, then the pinch bolts are likely to have been covered in oil sludge which inhibits corrosion to some extent.
-If your vehicle develops a leak around the oil pressure sender, do not bring the car to an uninformed aftermarket shop that will over-torque the oil pressure sender by a couple hundred foot pounds with a long pair of vice grip pliers. As this procedure is likely to cause hairline small fractures in the metal casting of the filter adapter making a large oil leak and causing engine damage from lack of lubrication
-A portion of the engine block and filter adapter had been covered in oil for an extended preriod. This is why some of the parts are less corroded than others
-It is in theory possible to leave the police oil cooler mounted to the radiator core support and replace just the filter adapter with it's civilian counterpart. But the cooling hoses on an older vehicle with many miles are going to be fatigued and are unlikely to seal properly to the new adapter
-Leaving the fan shrouds off the vehicle will cause the engine to run hot in traffic. no fan shouds = low air suction across radiator fins
-A goodyear gatorback accessory drive belt is pictured above. It has a distinctive ribbed appearance to it. And helps prevent belt slippage during wet weather operation.
-Some "mechanics" used to "repair" leaking oil cooler lines on the pre-1998 vehicles by unscrewing the hose fittings from the oil filter adapter and replacing them with solid brass plugs from the hardware store. This did indeed usually stop oil from leaking from the cooler lines, but it also forced all oil flow in the engine to pass through a small orifice inside the oil filter adapter intended for cold startup bypass. The reduced pressure from this procedure always seems to result in some sort of engine failure. And then the "mechanic" gets paid several more hours of labor to install a "new" engine in the customers vehicle a few months later.
-One bypass method that could work and not cause any damage to the engine would be to remove the hose fittings from the adapter and install a custom u-shaped adapter that redirected all fluid from one port to the other. A well stocked hardware store would likely have the needed parts in stock for this option.
-Do not attempt to "save a buck" by purchasing a "pre-owned" oil filter adapter from the salvage yard. The engine block side of the adapter has a finely machined surface that is likely to be damaged by salvage yard personnel during removal or transit. Damage may manifest itself as external fluid leaks onto the ground. It may also manifest itself as internal leaks that mix engine coolant with engine oil. Also keep in mind that the mating surface of these adapters can corrode as seen in the pictures above. And most salvage yards won't sell you an oil filter adapter seperate anyways, instead they will insist that you purchase a entire engine assembly.
-The oil cooler hoses for the pre-1998 crown vics have been discontinued and are no longer avaliable from ford as service parts. Attempting to order the pre-1998 hoses from your local dealership will result in a 1998+ oil filter adapter, 2003+ cooler hoses, and some miscallenous fasteners being ordered at a cost of a few hundred dollars. All 1992 and later 4.6L crown vic engines have the same mounting pattern where the oil filter adpater attaches.
-In hot enviroments such as california and arizona, there appears to be some incidence of fatigue of the gasket between the engine block and the filter adapter resulting in fluid leaks. Fluid leaks from this gasket are less common in the northeast where summers are cooler, but do happen sometimes.
-The fluid cooler hoses are constantly flexing as the vehicle is driven to allow movement of the vehicle's body in relation to the vehicle's frame
-The newer 98+ style police oil filter adapter obstructs one of the oil pan bolts. So on 1998+ vehicles, you have to remove the oil filter adapter prior to removing the pan bolts.
-Do not overtorque the bolts that retain the adapter to the block or you'll risk cracking the adapter. Also remember to torque the bolts in the proper application pattern.
-An "oil change" is recommended after replacing the filter adapter.

Part Number
Suggested Retail
(August 2005)
3W7Z-6A715-AA Police Oil Cooler Hose Assembly
Later style. Bolts onto oil filter adapter. No spring locks.
This part is used on 2003+ production vehicles. These hoses are slightly longer in length than the 1998-2002 service part that they supercede.

Oil cooler hose seals not serviced seperatetly from the hose assembly
F8AZ-6881-AA Police Oil Filter Adapter
With Oil Cooler
F6AZ-6840-BA Police Oil Filter Adapter -> Engine Block Gasket
With Oil Cooler
(Blue colored gasket)
(Ford service parts literature indicates that the blue gasket is factory installed in police cruisers. But many police interceptors have the orange gasket factory installed instead.)
N806155-S2 Police Oil Filter Adapter -> Oil Cooler Hose Bolt
M6 x 1.0 x 27.5
This bolt retains the oil cooler hoses into the filter adpater.
3W7Z-6A642-AA Police Oil Cooler
This is the aluminum oil to coolant heat exchanger that interfaces with the lower radiator hose and the cooler lines. It is physically located below the radiator.
F5AZ-6B634-A Police Oil Cooler -> Radiator Core Support Bracket
1995-2002 (Not compatible with 2003+ crown vics)

Oil cooler hoses for 1995-1997 crown vics no longer serviced. Must upgrade to later style F8AZ-6881-AA filter adapter, 3W7Z-6A715-AA hoses, and N806155-S2 bolt.

F1AZ-6881-BA Civilian Oil Filter Adapter
Without Oil Cooler
F6AZ-6840-AA Civilian Oil Filter Adapter -> Engine Block Gasket
Without Oil Cooler
(Orange colored gasket)
(Ford service parts literature indicates that the orange gasket is only for civilian cars. But many police interceptors have the orange gasket factory installed too.)

Oil Filter
Police and Civilian
22mm Fitting
(Also used in numerous other ford vehicles besides the crown vic)

N806156-S437 Oil Filter Adapter->Engine Block Bolt
These are the bolts which retain the oil filter adapter to the engine block
M8 x 1.25 x 41.0
Supercedes N806156-S2 and N806156-S309

Oil Pressure Sender
Police and Civilian
Older style electrical connector for 1999 and prior vehicles
Oil Pressure Sender
Police and Civilian
Newer style electrical connector for 2000 and later vehicles

Oil Pan Drain Plug
The threads  sometimes "strip out" when you remove the plug from the oil pan
Having weak threads on the drain plug and strong threads on the oil pan is desirable since the drain plug is very easy to replace in relation to the oil pan itself

Police hose assembly 3W7Z-6A715-AA (2003+. slightly longer than 1998-2002 part) $122.05
Gasket without Oil Cooler F6AZ-6840-AA $11.52
Gasket with Oil Cooler F6AZ-6840-BA $7.91
Police Oil Filter Adaptor F8AZ-6881-AA $268.98
Civilian Oil Filter Adapter F1AZ-6881-BA $119.71
Oil Filter Adapter->Engine Block Bolt  N806156-S437 (Supercedes N806156-S2 and N806156-S309) (M8 x 1.25 x 41.0) $5.74
Oil Cooler Assembly 3W7Z-6A642-AA $393.57
Oil Filter F1AZ-6731-BD FL820-S $7.24
Oil Cooler -> Radiator Core Support Bracket F5AZ-6B634-A $22.32
Oil Adapter -> Hose Bolt N806155-S2 M6 x 1.0 x 27.5 $9.08

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