If you are going to buy/drive a 6.0L, then you really need a good scan toll that can give you some engine vitals (PID information to watch periodically when driving). ScanGauge makes a couple of good ones, but they are not the best if you really want to dive into troubleshooting a 6.0L. For that you really need FORScan.
In fact, you should have a good scan tool when going to buy a used 6.0L, and learn what to look for before you buy. There is a good link on this at the end of this post on buying a good used 6.0L.
The thing about buying a 6.0L is that they are old, and what you buy may have been abused. Abusing them can involve running them with poor cooling and excessive heat, which can do quite a bit of expensive damage.
If you are renovating a 6.0L, make sure you know the health of the oil cooler before taking off parts and replacing them (if this is possible). I am ok with the OEM oil cooler ASSUMING the coolant has been changed to an EC-1 rated ELC coolant AND the differential temperatures between the oil and coolant are within proper limits to begin with.
If you want to splurge, the external oil cooler system from BulletProof Diesel is fantastic - just expensive.
The '04.5 model years and up had weak EGR coolers - period. You need to remove the OEM one and install one from BulletProofDiesel.
FICMs can fail and then they can be repaired AND upgraded. If buying a used 6.0L, add to the price (in your mind) $400 or so for a FICM rebuild by FICMRepair.com or CircuitBoard Medics. As stated above, low system voltage can ruin the FICM power board, but it can ALSO ruin the FICM logic board (and a logic board failure is not easy to detect (ie will not be definitively identified by ANY PCM PIDs or the buzz test). Having a known good spare FICM isn't a bad idea.
The 03 and 04 HPOPs (all of them) are a weak design. Do not go back in with an OEM one. Get one from Dieselsite or CNCFab.
The 04.5 model years went to a different oil rail system (high pressure oil system feeding the injectors). Especially when exposed to heat, you can get leaks. I would recommend the Dieselsite standpipes and dummy plugs for these model years (and newer). These use Viton for the o-rings and
at best the OEM ones use HNBR (not as heat tolerant).
Excess heat can cause heads to warp and even crack. Machining heads is risky because they already are structurally on the edge (especially from inadequate number of bolts). There is a minimum thickness spec for the head. There are also a lot of junk heads on the market. I prefer the KillDevil Diesel heads (steel OR aluminum).
The block deck needs to be flat also for heads to seal. The surface finish on the block deck and heads is critical also. There are specs on this.
I like FelPro head gaskets, but they may not be compatible with the o-ring work that some shops do on 6.0L heads (ie where the shop physically locates the o-ring may not match the FelPro gaskets design). OEM head gaskets are generally pretty good as an alternative.
The fuel pump pressure regulators from the factory were weak, and low fuel pressure was found to be a major cause of injector failure (injectors are expensive). Ford/International came out with a reasonable priced upgraded spring.
My 2006 is still running very well, and on the original injectors (almost 250k miles)! I do use a fuel additive about half the time. I can not say if it is responsible in any big way to my injector longevity. I just add it when it is handy and I remember it.
Filtration is important to these engines (fuel and oil). Do yourself a BIG favor and stick with OEM fuel and oil filters. This also means you need an OEM oil filter cap. Some people by aftermarket combo cap-and-oil-filter and then ignore the "Do Not Reuse" labeling on the cap and throw a different oil filter in it. This can result in the inadequate closing of the oil filter housing drain valve. This can starve the high pressure oil system AND can also reduce the flow of lubricating oil.
Other fuel system issues encountered over the years:
1. If a cab and chassis design, the fuel tanks were coated internally. Over time these coatings failed, peeled off, and plugged the fuel filters and system. Remember what I said about low fuel pressure!
2. The fuel tank pickup tube is plastic and degrades over time. This can create plastic bits to plug up things and can cause fuel not to be drawn up the tube when the fuel tank gets to about 1/4 level. Remember what I said about low fuel pressure. I installed a sump after my pickup tube failed. Remember what I said about low fuel pressure!
3. The fuel pump has a relay that is integrally soldered onto the Central Junction Box board. It likes to fail. It is not a DIT repair (unless you are well versed in circuit board repair techniques). Send to CircuitBoardMedics. Remember what I said about low fuel pressure.
Lots of cheap (poorly remanufactured) 6.0L injectors on the market! I would not buy remanufactured injectors from anyone other than FullForceDiesel, or CNCFab. CNCFab sells completely new 6.0L injectors also. They MUST be made by Pure Power (the OEM company formed to manufacture the 6.0L injectors in the first place). Alliant has an agreement with Pure Power to market them. Stay away from places like Pensecola Fuel Injection, Sinister, and even Warren Diesel (WDI) has had more problems that I would accept - although they (Warren) do have good customer service.
The control modules (especially the FICM) like good voltage - make sure the batteries and alternator(s) are in good health. Also, makes sure all cables and wiring, and terminals (including the grounds) are in good shape and solidly attached (with no rust).
My transmission is still original and has had no issues. I change the fluid and external filter every 30k miles. In fact, my fluid change process is a series of 4 drains and re-fills (with enough driving in between to fully mic the old and new fluid). One thing to remember is that it is impossible to fully drain the 6.0L fluid reservoirs. They will always retain a significant amount of the old fluid after a drain.
Draining the oil will get 14/15 quarts out of a system that holds 18 quarts. There will always be a residual of the old fluid left in the system. Draining the transmission fluid will get 8 quarts out of a system that holds about 17 quarts. Draining the coolant will get about 13/14 quarts out of a system that holds 27.5 quarts!
Oh - and VERY important to use the correct transmission fluid!
The 6.0L can be a really good engine platform, they just have quite a few "special needs".
And you would be way better off starting with a good one:
