7.3 Power Stroke Bypass Oil Filter System

Contents
  1. Full Flow vs Bypass Filter Systems
  2. Oil Filter Micron Ratings
  3. Bypass Oil Filter Recommendations
  4. Bypass Filter Mounting Options
  5. Bypass Oil Filter Installation Procedures

Applicable Models:

1994.5 - 1997 Ford F-250, F-350, F-Super Duty
1999 - 2003 Ford F-250, F-350, F-450, F-550 Super Duty
2000 - 2003 Ford Excursion
2000 - 2003 Ford F-650, F-750
1995 - 1999 Ford Econoline E-350
2000 - 2003 Econoline E-350, E-450, E-550

Applicable Engine(s):

7.3L Power Stroke V-8 diesel (7.3 DIT, T444E)

Full Flow & Bypass Oil Filtration Systems

It takes very little time for the engine oil in your 7.3L Power Stroke to take on a deep, dark, charcoal color. It may even seem like new motor oil takes on a dark appearance shortly after it is poured into the crankcase. Engine oil normally turns black in any diesel engine as a the result of microscopic soot particles entering the crankcase during blowby. Since engine oil never actually drains completely when it is changed you're clean oil quickly mixes with any residuals, turning it black rather quickly. Even the most precise piston rings are far from a perfect seal, thus small quantities of fuel, exhaust gases, and other combustion byproducts are able to pass through the ring gaps and clearances between the cylinder walls and the piston rings. As an engine wears, blowby typically increases and you'll find the rate at which these contaminants infiltrate the crankcase increases proportionally.

For these reasons, unimaginably small soot particles contaminate an engine's oil supply and are carried throughout the engine. Although tiny, soot particles are considered relatively abrasive and the presence of soot in the engine oil is a real concern contributing to accelerated wear and even cylinder wall scarring. To some degree, the presence of soot is entirely normal, unavoidable, and to be expected. Under ordinary conditions, normal soot infiltration should not compromise the long term reliability or integrity of an engine if maintenance is performed routinely at the manufacturer's recommended service intervals.

An engine's primary lubricant filter is a full-flow type. It is limited in the particle size that it can effectively capture because, as a general rule, the flow efficiency of the filter decreases relative to the minimum particle size that can be captured. In simpler terms, the filter media must become more restrictive to capture finer particles. Since engine lubrication is vital to its health, there must be a trade-off between filter flow and filtration efficiency.

A bypass oil filter is a partial-flow filtration unit with the ability to capture significantly finer particles than an engine's full-flow lube oil filter. Ford's advertises that its Motorcraft FL-1995 (now superseded by FL-1995-A) can filter 98% of particles 18 microns and larger. This means that this filter captures at least 98% of all particles 18 microns and larger in size. The Amsoil EaBP90 bypass oil filter, for comparison, is rated at 98.7% efficiency at capturing particles 2 microns and larger; an 800% improvement with regard to particle size. However, at this degree of filtration the filter would not suffice as a primary lubricant filter because it would be largely restrictive, impeding the vital flow of oil through an engine.

Bypass oil filters only handle a small amount of the sump capacity at a time. The flowrate through a bypass filter is designed to be low enough not to rob oil flow from an engine's lubricant circuits, but substantial and steady enough to effectively improve the condition of the engine oil. Primary full-flow oil filters perform their role adequately and thus a bypass oil filtration system is not a necessity; it's an insurance policy with the goal of maximizing longevity. Some oil contaminants, such as certain classifications of diesel soot, are simply too small to be filtered by a standard full-flow oil filter.

One side of a bypass filtration system is connected to a pressure port in the engine's lubrication circuit. Engine oil flows through the filter and is returned to the sump via an engine oil return port, the engine oil fill cap, or through the valve cover. This type of system does not interrupt or make significant changes to the flow performance of the primary lubrication system. Bypass oil filters typically last considerably longer than full-flow oil filters and are not replaced with every oil change.

Oil Filter Micron Ratings

A micron is a unit of measure equal to 0.001 millimeters, or roughly 0.00004 inches; an incredibly small unit of measurement from the human perspective. 1 micron is significantly smaller than any unit of measure used in even the most precise machining and manufacturing processes because it is simply too small to measure with standard equipment. For reference, a human hair is typically around 50 to 100 microns in diameter. Case in point, when filtration ratings are given in units of microns they refer to extremely small particles that are not visible to the naked eye.

Engine oil filters, like similar filtration products, are rated based on their micron rating (the smallest particle that can be captured in units of microns) and the efficiency at which it can filter particles of this size. A filter with a small micron rating and a high efficiency is desirable. For example, a 20 micron rating at 99% implies that the filter will capture and retain in its media 99% of all particles 20 microns or larger in size.

7.3 Power Stroke Bypass Oil Filter Recommendations

By our account, Amsoil remote-mount bypass filter systems are one of the more popular bypass filtration options for the 7.3L Power Stroke. With this kit, the bypass filter is mounted to the body or chassis in the vicinity of the oil supply port located on the rear oil cooler header above the factory oil filter mount. Amsoil also offers a dual bypass unit, which attaches to the factory filter base and relocates the full-flow oil filter alongside the bypass filter. We recommend the remote mount units, as the range of mounting options provide greater flexibility, access, and ease of maintenance.

Amsoil Kit BMK21 Overview:

  • 180 degree mounting range (from vertical to horizontal, cannot be installed inverted at any angle or upside down).
  • Bypass filter can be mounted anywhere within 6 feet of oil pressure port (supply/return hoses cannot exceed 6 feet in length).
  • The smallest compatible bypass oil filter (EaBP90) requires replacement at 60,000 mile/600 hour/2 year intervals. The largest compatible bypass oil filter (EaBP110) requires replacement at 80,000 mile/1,200 hour/2 year intervals.
  • Bypass system draws approximately 10% of oil system flow.
  • Bypass filters (all sizes) are 98.7% efficient at removing 2 micron particles.
  • Spin-on, canister type oil filter for easy replacement.

Bypass Oil Filter Mounting Options

In all probability, selecting a suitable mounting location for the bypass filter is the principal step in installing such a system. Although the system flows much less oil than the full-flow circuit, damage to the filter could prove critical. It needs to be protected from debris, heat, and road hazards in a similar fashion that the full-flow filter is. Take the following into consideration when finding a preferred mounting location:

  • The filter must remain accessible so that it can be changed at regular intervals.
  • The supply/return hoses should not exceed 6 feet in length. As a general rule of thumb, the closer to the full-flow oil filter, the better.
  • If the filter is to be mounted horizontally, note that it is going to leak significantly more oil during removal than if it is mounted vertically.
  • The filter and its hoses should be protected from excessive sources of heat (i.e. exhaust system components).
  • The filter should be protected from road hazards and debris that it may come into contact with (also consider mud flung from tires). If the vehicle is used off-road, the filter should be positioned so that it could not come into contact with rocks, etc. If the vehicle is used to ford water, the filter should never be in a position where it will be submerged.

Common mounting locations are against a body panel, frame rail, or cross member. We prefer to position the filter on the inside of a transmission or transfer case cross-member. Although more difficult and not always optional on four wheel drive vehicles, this places the filter in a safe space where it could never be crushed or ruptured. The underside of a body panel or side of a frame rail would be secondary options but are largely suitable; we recommend positioning the filter so that it does not hang below the lowest part of the body and frame.

How to Install a Bypass Oil Filter on a 7.3 Power Stroke

Click any thumbnail to view fullsize, detailed image

mounting bypass oil filter
  • Select a suitable mounting location (refer to advice above). Drill mounting holes for the filter base and test fit the location, ensuring that the oil filter is accessible and there will not be any issues running hoses to and from the rear oil cooler header (you cannot run the hoses over the top of an exhaust pipe, for example).
oil supply pressure and drain port locations
  • Remove the engine oil filter and drain the engine oil.
  • Locate the oil supply (pressure) and return (drain) ports as labeled in the image at left.
  • Remove the oil supply port plug with a 7/16 inch socket.
  • Remove the oil return port plug with a 5/16 inch square drive socket.
oil supply and drain fittings installed
  • Install a 3/8 npt to 1/8 npt adapter into the return port; use Loctite 545 or equivalent oil resistant thread sealant.
  • Install the supplied 1/8 npt x 7/16 JIC flare fittings into the oil supply and return ports; use Loctite 545 or equivalent oil resistant thread sealant. Do not overtighten the fittings, the rear oil cooler header is particularly vulnerable to cracking if the fitting is overtightened.
fittings installed on bypass oil filter base
  • Install the supplied 1/8 npt x 7/16 JIC flare fittings into the appropriate ports on the bypass oil filter mount (base). Depending on the intended mounting location, a combination of angled (elbow or 45 degree) fittings can be used to adjust the position of these fittings and prevent the hoses from kinking.
cutting oil hoses to length
  • Measure the hose for the supply and return lines - if either line requires a length of over 6 feet, the mounting location is not suitable.
  • Measure and cut the supplied hose in half (resulting in two equal length hoses). Note that all cuts should be done with a sharp razor knife and should result in nearly perfect straight cuts (i.e. no irregularities or harsh angles).
preparing hose fittings
  • Disassemble the field assembly type JIC hydraulic hose fittings (there is no crimping required for the installation of these hoses).
installing hose fitting collar
  • Install the hose fitting collar by threading it onto the hose counter clockwise until it bottoms out, then back it off 1/2 turn (clockwise).
installing barbed hose fitting
  • Lubricate the barbed end of the JIC fitting with clean engine oil.
securing hose fittings
  • Insert the barbed end of the JIC fitting into the hose while rotating clockwise.
fittings attached to oil hose
  • Tighten the barbed section of the fitting against the collar until it bottoms out and the fitting is secured to the hose.
  • Repeat for the second hose so that you have two lengths of hose with fittings at one end only.
oil supply and drain hoses attached to bypass filter base
  • Loosely install the supply and return hoses either at the filter mount or supply/return ports; whichever is more convenient.
  • Measure and mark each required hose length. This is best done by routing the hoses (one-at-a-time) into the desired position, leaving enough slack that the hoses can be secured at several points (i.e. cable tied to the frame rail).
  • Label the supply and return hoses so they are not confused during installation; their lengths are likely different.
oil hoses wrapped in protective sleeves
  • With the hoses now cut to length, install the appropriate JIC flare fittings at the bare ends of each hose.
  • We took an extra step and installed hydraulic hose sleeves and radiant heat shielding on the hoses. These items are not terribly expense and should be available at your local hydraulic hose shop.
oil hoses attached to engine block and oil cooler header
  • Install the supply and drain hoses, ensuring that the flare fittings are tightened snug.
  • Finish changing the engine oil and install a new primary oil filter.
  • Install the bypass oil filter.
  • Reference the selected bypass oil filter and add the appropriate amount of additional engine oil. Your new engine oil capacity is 15 quarts plus the capacity of the bypass oil filter. For Amsoil bypass filters, EaBP90 adds an additional 1 quart, EaBP100 adds an additional 1.5 quarts, and EaBP110 adds an additional 2 quarts of engine oil.
  • Verify engine oil level, then start the engine and check for leaks. After 2 to 3 minutes of runtime, shut off engine and recheck the engine oil level.
Summary
  • A bypass oil filtration system has the ability to filter significantly smaller particles than a standard full flow oil filter.
  • Cleaning engine oil beyond OE standards can reduce wear by removing extremely fine, abrasive particles from the engine oil.
  • The bypass oil filtration system only handles a inconsequential volume of engine oil at any given time, thus having minimal effects on engine oil pressure and flow through the primary lube circuits.