I'm fairly tired of all the mis-information regarding the 6.0L diesel. Here is my input.
I was a 7.3L guy through and through. I've had 6 of them, all with minor issues and only one with a major issue (dropped a valve). None of them were "trouble free" like people state. Every engine needs repairs, pure and simple. The plus side to the 7.3L, is most of those repairs are easy enough for a guy with good mechanical skill to do in his driveway.
Here is why I now own a 6.0L diesel and not a 7.3L.
I was on the hunt for a nice, clean 7.3L. The market for them is absolutely insane. In my opinion, they are way overpriced for what they are. A 2002 or 2003 rust free 7.3L crew cab, long bed, 4x4 with 150K miles will fetch about 16-17K dollars. That's ridiculous. I have driven a 2005+ coil sprung superduty many times and the ride is so much better than the <2003 superduty that it would make it tough to go back to the "old truck". Not to mention, the coil sprung front end makes the turning radius far better than the leaf springs. This is critical for towing. Keep in mind I won't compare a 2003-2004 6.0L in this post. 2003-2004 6.0L had a considerable amount of issues, combined with the leaf sprung front suspensions, and older front facia, do not make a very ideal combination.
So, I started reading about the 6.0L. There are 5 major complaints. Lets start off by saying the worst thing for a 6.0L is daily driving it empty 10-15 miles to work. If that is your daily routine for the truck, don't buy a 6.0L. If you are looking for a diesel that you can drive like you stole it and tow a ton, you'll like the 6.0L. For the record, I am pulling 21K (combined truck and trailer) with my truck and it is smother than my old 7.3L pulling 15K combined.
The EGR cooler gets built up with carbon and doesn't flow correctly. It can also get plugged with sand from the coolant (see fix below). When it plugs, you run the risk of blowing head gaskets. If you tow a lot or push the truck, the EGR will remain cleaner than if the truck idles a lot. Again, the truck likes to be pushed hard. Many retailers have developed EGR delete kits, or bulletproof EGR coolers.
– The oil is tied into the coolant system; the coolant helps cool the oil. There is a problem with the 6.0L having sand in the casting from the factory. The sand ends up blocking the oil cooler and oil temps spike out of control. This causes oil leaks, turbo issues and even coolant related issues due to lack of flow. The solution is fairly simple - Put a DIY coolant filter in place. A full kit is about $120, but some people claim to build them yourself for about $50 and after 5K-10K miles (and 3-4 filter changes) the sand will be 100% removed.
– The 6.0L has a variable vain turbo, unlike the 7.3L. A variable vane turbo can change the angle of the blades to maximize boost/efficiency. If the truck isn't pushed hard, the vanes won't travel their full path very often. If that happens, carbon gets built up in certain places between each vane. Once the turbo gets carbon built up inside it, the vanes can become stuck and you run the risk of overboost, and blowing the headgaskets. This seems to be most likely on 03-04 engines. Again, if you push the truck hard or tow with it, the turbo vanes will travel full sweeps to keep the turbo clean. If you drive the truck light, you have a higher chance of building up carbon. Ford eventually put in a "turbo dither" calibration that forced the vanes to travel a full path on shutdown to prevent carbon build-up. Turbo failures on post 2005 trucks are fairly rare (or the same rate as a 7.3L). If you have a 2003-2004 turbo, drive the truck like you stole it and you won't have this issue.
– the head bolts aren't actually an issue themselves, the issue is when other parts fail (EGR and turbo) and stress the head bolts. The ARP headstuds should be put in to place just to protect the heads incase other parts fail.
- People complain about the 03 and 04 injectors failing. The injectors cost the same as 7.3L injectors, and once they are replaced, are fairly trouble free. Keep the oil changed and you should be fine. Again, 2005+ trucks tend to have less issues.
So… aftermarket companies like Sinister Diesel have developed kits that address a lot of these issues.
They will take care of the EGR, oil cooler, and headstuds. The kit is ~$1400 ($1800 with a tune, which can put you at 400hp and turns off the EGR OBD system to turn off your check engine light) and a shop will charge about 2500-3000 to install it (some cheaper).
So back to why I bought a 6.0L…. It is still very easy to find rust free (or close) 2005-2007 trucks with the 6.0L, and in a lot of cases, they are the same price as a rust free 2002 or 2003 7.3L. You can put $4400 into repairs/upgrades into a 2005-2007 6.0L and have a very reliable 400 hp, 675+ ft lb diesel that is quiet, comfortable, turns great, rides nice, doesn't pollute, etc. The 6.0L intake/exhaust/auto trans can support 500hp, so no worries there. Stock injectors can support 400 hp.
Or you can buy a rust free 7.3L and put $1500 into intake, exhaust, gauges and a tune and you might be able to squeeze out 300 hp/ 575 ft lbs from it. Anything more than that and you need injectors, oil pump, turbo, and a $3500 trans.
In my opinion, the 6.0L is one of the few engines that if you know what you are getting into prior to purchasing one, and you convince yourself you need to put $4500 into it right away (most people struggle with that),
then you will be very happy with your purchase. The 2003-2004 6.0L made a very rocky road for the 2005-2007 6.0L trucks, which have far less issues.