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Retired life where he’s just the driver

Our F350 Reliability and Maintenance

I’d like to make several general comments to address the terms used when discussing vehicle issues. My point is that many of these terms are commonly mis-used (and therefore commonly mis-understood).


MAINTENANCE is the periodic service and replacement of ‘wear items’ on a vehicle. This includes lube/hydraulic oil/filters, air filters, coolant, brake pads/rotors, wheel bearings, universal joints, etc. Service life of ‘wear items’ is less than the life of the vehicle AND they require regular inspection/replacement at know/specified intervals. If not specified, they can be estimated.

REPAIR is the correction of unanticipated faults. It involves 1) troubleshooting to identify the faulty system or part, 2) determination of the root cause failure and 3) the effect to related systems. It is not uncommon for a fault to produce a chain of failures before it becomes noticeable.  A proper repair requires the ability to verify the root cause and a thorough verification of operability of directly affected and related systems. ‘Guessing’ and ‘swapping parts’ until the symptom ‘goes away’ has no place in the repair process because without a known root cause, it is impossible to determine all parts that are affected/damaged.

QUALITY is the ‘conformance to design’. It is a measure of how true the part was manufactured to the intent of the designer. It is not a measure of performance (implemented by the design). Frequently, users declare a higher performance part as ‘higher quality’, since a user cannot know the performance level intended in part.

RELIABILITY is ‘quality over time’. Otherwise, stated, ‘presuming it does work, does it keep working?’. We assume, if it worked initially, and it will continue to work for some additional time… long is the question…and a factor of design. ‘Cheaply made’ parts are, by design, intended to operate correctly, just over a shorter design life. They are not ‘low quality’ because they fail early (er), they are simply less reliable (do not perform consistently over a long period of time).

Shortcomings with the 6.0l diesel engines used on the 2003-2007 Ford ‘Superduty’ trucks typically start from small, simple failures that do not become apparent until they effect several additional systems. This can likely be the case with any complex mechanical system. The root cause can often be prevented or detected if the ‘cascade failure’ of the specific system is understood. This led me to pursue a number of specific improvements to mitigate or monitor systems that are prone to problems. 

Where it all started

THE 6.0l ENGINE spawned a broad base of aftermarket businesses based on the shortcomings of the engine. In the 10 years since the it ceased being used in production vehicles, it can be fairly said that all its shortcomings are known and most have been addressed by the OEM or aftermarket modifications.  In my investigation of the 6.0l engine, I think there are relatively few and detectable problems that  lead to more serious and costly ‘cascade failures’ that are the basis for the costly major repairs and bad reputation of the truck. I have invested considerable time, money and effort learning about and taking steps to monitor or avoid them. 


One of the most frequent failure modes starts with the engine overheating due to several unrelated mechanisms but generally precipitating the same series of failures, depending on how far down the chain a problem is detected.  

A common mechanism begins with clogged coolant passages in the fin-plate oil cooler. It is caused by a design flaw of small coolant channels in a commonly used design ‘fin-plate’ heat exchanger, not commonly used in automotive engines. The failure mode begins when coolant borne contaminant particulates become trapped and build up in the quite small coolant channels. This reduces coolant flow through the whole engine. A second mechanism is a weak, molded plastic coolant pump impeller that wears or breaks. In either case, with low coolant flow, cascade failures begin;  

  1. Inadequate coolant flow in the Exhaust Gas Recirculation (EGR) cooler (immediately downstream of the oil cooler) cause the small amount of coolant to boil away, leaving no coolant at the exit end of the heat exchanger.
  2. Without coolant flooding the heat exchanger,  high temperature exhaust overheats and cracks coolant tubes in the exchanger.
  3. Once broken, 20-30PSI pre-turbo exhaust enters the 15PSI cooling system. Exhaust causes further coolant contamination resulting in accelerated oil cooler blockage.
  4. High pressure exhaust increases cooling system pressure, forcing coolant into the degas bottle, reducing coolant volume in the engine. Failure-prone early OEM coolant degas bottle cap pressure relief valves facilitated coolant escape. The first detectable symptom is low coolant level but is only visible if checked.
  5. When the engine, with a highly pressurized coolant system is shut off, coolant leaks into the exhaust side of the EGR cooler. The next time the engine is started, it creates a ‘steam cloud’ out the tail pipe and further loss of coolant in the system. This is the first highly visible symptom but is short lived and often missed.
  6. The overall loss of coolant and its circulation lead to higher engine temperature which over stress the head bolts, leading to head gasket failure. This is the third visible symptom that results in loss of power and poor driveability. Unfortunately by this point, multiple systems are compromised and repairs can top $10,000.


OBD and Tablet running Torque

Probably most importantly, I have an Android tablet mounted to the dash and linked to the vehicle’s ‘On-Board Diagnostic’ port (by Bluetooth) where I monitor a host of sensors including engine coolant and engine oil temperature. I check to see that the oil is no more than 15 degrees hotter than the coolant.  A differential over 15 degrees regularly or for any extended period, identifies a potential clogged oil cooler. With the heavy loads my truck bears carrying the camper and towing the Jeep, it frequently bumps up against the maximums but usually only when climbing hills at speed and quickly recovers.

I also monitor the absolute temperature of the coolant to insure the engine is not nearing an overheating situation. The tablet app (Torque Pro) has alarms that can alert me audibly and visually to any threshold I set. I have factory instrument cluster equipped dash gauges for both engine coolant and transmission oil temperature that seem to always sit in the mid-range regardless of the true temperature (display on my tablet by the factory engine sensors). This tells me, they are either inaccurate (probably operating as intended) or ineffective (most likely). If not for my ability to accurately see actual temperature, I would surely have assumed they were working accurately (enough). I also make a judgement of overall temperature vs. load to verify the cooling system is performing adequately and consistently. Several aftermarket manufacturers make aluminum impeller water pumps and Ford has improved their own design to improve reliability. I will likely replace the water pump in the near future as a preventive measure.

Tablet running Torque

The tablet app (Torque Pro) has alarms that can alert me audibly and visually to any threshold I set.


Another failure mode has to do with insufficient fuel delivery to the injector system. The primary fuel system (tank to injector system) has a tank inlet screen, two fuel filters and a ‘Horizontal Fuel Conditioning Module’ (HFCM) which is a frame rail mounted electric pump/filter/water separator to deliver diesel to the injector system. If primary fuel pressure drops below 45psi at any time, injectors will not be able to fill with enough fuel to operate correctly and the high pressure oil that powers the injection will cause damage. The truck’s native control system only operates a water detection sensor in the HFCM. It has no way of monitoring the pressure anywhere. The factory has installed a pressure test port at the output of the pressure regulator on the bottom of the second filter bowl but this is only a diagnostic connection for problem diagnosis. Loss of fuel pressure can occur from clogging of the fuel pickup screen, clogging of either of the 2 filters or failure/weakness of the fuel pump. The most common cause is failure to periorically replace the fuel filters. There are no sensors or alarms for low pressure conditions and failure is only likely to be noticeable after multiple injectors (costing ~$400 each) have been damaged. Ford has changed the pressure regulator spring to increase pump delivery pressure (referred to as a ‘blue spring kit’) from 58psi to 65psi. This helps overcome some of the potential shortcomings but is more likely just to delay them. 

To protect from the injector damage that can stem from low primary fuel pressure, our engine has;

A new pressure regulator spring (but not the one that increases fuel pressure aka ‘blue spring’). I feel that as long as I can monitor the pressure, it’s not really necessary or a good idea to increase it.

  •  I installed a mechanical pressure gauge directly in the dash, showing primary fuel pressure constantly. undefined
    I usually check it when starting (key on/engine off) and when under the highest engine loads (climbing a hill with  a load) to make sure my fuel pressure is more than 50psi. I have never seen it below about 52 but if it were to ever drop below 50,  I would immediately change filters.
  • I replace the fuel filters every other oil change with OEM filters (~$40). Aftermarket filters have been shown to separate and bypass fuel or fall apart and clog the filter system. I learned of this 3 months after replacing the filters with the cheapest thing I could find (~$21). I immediately replaced them again with OEM filters and found that the first filter had begun to fail in 2 places.  I am 15k miles into the current filters and have seen a slight but steady pressure drop of about 3psi which is expected. 
  • The HFCM has a water drain plug that can be removed to drain separated water. It is only necessary if the sensor detects water. Removing the plug usually means you get an arm or face full of fuel so is an unpopular remedy. The plug is hard to access in a 4WD because the frond driveline pass close by it. I did get an alarm early in my ownership of the truck and pulled the plug to drain it but saw no water. The alarm in the separator has a history of reporting (supposedly)  false alarms. This has resulted in Ford issuing a field modification order to disconnect it.  I noticed that when I removed my plug, it had a serous amount of metal missing due to what appeared to be rusting. While I don’t imagine water is a frequent problem, I want a way to know about it and deal with it so I have kept the alarm installed and replaced the plug with an aftermarket brass fitting that has a Schrader valve mounted in a 3/8 flare fitting (standard air conditioning fitting) that I can easily attach a refrigerant hose to and drain to see if water is present.


Were a very new thing in automotive engines and in this engine in particular when it was developed. It has several failure modes that are relatively easy to detect with sensor data available in the OBD II system. Solutions to the detected problems are not often easy to correct but there are several maintenance steps that can avoid problems. The evolution of diesel injection from mechanical pumps to electronically controlled, hydraulically powered designs mean the engine has both a high pressure oil pump (to boost engine oil pressure into a circuit to supply the injectors up to 4000psi) and a high voltage power supply (~48V) to actuate the injectors.

 The ford specific PID’s in the OBD II report data on the pump output pressure (HPOP – High Pressure Oil Pump, oil psi), pressure sensor voltage (ICP – Injection Control Pressure Regulator, 0-5V), pressure regulator opening (IPR – Injection Pressure regulator, 15-85% open), injector power supply high voltage (FICM voltage, ~48V) and input voltage (FICM vehicle, ~13V).

All of these data points can be use to monitor the health or identify malfunctions in the system. I have a second page in my tablet for the fuel injector system data.

In addition to monitoring the stats of the system, some preventive measures can be taken. A common issue with the fuel injectors known as ‘stiction’ causes injectors to be slow to react when the engine is cold. Friction modifiers are commonly added to engine oil (because it is also used to actuate injectors) to maximize the lubricity of oil side of the injectors and the fuel to maximize the fuel side of the injectors. I use Archoil AR9100 (~$40 per oil change) oil additive with Shell full synthetic diesel rated oil in each oil change and AR6200 (~$.01/gallon) fuel additive with every other tankful of fuel.

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