I thought I would re-post this since I have seen a few threads on the subject:
My personal preference is to go for a 2006 or 2007 year model (but really ANY year model low-mileage 6.0L might be worth looking at) - folks WILL DEFINITELY bargain with you. I think that buying a used 6.0L can turn out to be a good deal - if you are wise about the pre-purchase inspection! If you find a good price AND you have checked into the reputation of a local independent shop or dealership on repairing the 6.0L (or if you can do repairs and upgrades yourself) - then GO FOR IT! So much depends on having a competent and honest dealership, a trustworthy independent shop, or personal mechanic skills to troubleshoot and work on any POTENTIAL future problems.
Edit:
IMO everyone should have an electronic scan tool BEFORE going to look at a used 6.0L. The cheapest way to go about this is to download either Torque Pro or ForScan Lite to your phone. I find the Torque Pro interface to be better, but ForScan is by far a better code reader. To use these apps, you will need an ELM327 OBDII adapter. I find that the BAFX adapter is very reliable. WiFi works well w/ i-phones and probably also works well w/ Androids (I haven't checked that). BlueTooth works well w/ Android phones. The app and the adapter will cost around $45 total. Very cheap investment for the value you get!!! A little more on this topic later in the thread!
If you are looking at used 6.0's here are a few considerations (along w/ the CARFAX reports).
Some 6.0L weak points (things to check):
Look for signs of coolant degas bottle overflow (dry white residue on and around the degas bottle or no level in degas bottle).
Lots of idling can cause EGR problems. The 2005 and up model years have engine hours as a possible display. I would look at the hours on the engine (if it has this monitored) and divide the miles by the hours (is it below 25? If so, may have had lots of idling).
Even without much extended idling EGR valves can plug quickly (if it is still stock). In fact, if it is still stock, I would negotiate to pull the EGR valve to inspect it (have them show it to you when it is out and then you need to look into the intake). Check for wetness (w/ rear end jacked up or the truck parked on a "decline") and for excess soot. Wetness could indicate an EGR cooler leak that is common w/ 04.5 and up model years (it could also be excess fuel and indicate injector and/or combustion problems). If the valve is gunked up, have them replace the valve. If the intake is real bad, you may push them to clean it as well.
Look underneath for oil leaks - some trucks have had a lot of them.
Try to find out about the routine maintenance:
· Filter change intervals on time? What kind of oil has been used? (needs to be CI 4 + or CJ 4 rated, and now CK is the rating). Synthetic or conventional oil? 15W40? 5W40? 10W30? IMO synthetic 5W40 or a quality 10W30 is best.
· OEM filters? Look at them and see what kind they are. Aftermarket filters can cause MAJOR problems. A tall oil filter cap is a tell tale sign that the owner didn't really know how to care for the truck properly. A tall cap and an OEM filter can result in low oil pressure and unfiltered oil. WIX filter/cap combination has been the main issue - usually when someone re-used the cap.
· Find proof of Transmission being flushed/changed - it is recommended every 30,000 miles.
· Any exhaust problems visible (i.e. lots of white or blue smoke)? White smoke may mean an EGR cooler leak if the smoke smells like coolant or a sign of injector issues if the smoke smells like fuel.
Check for any FLUID leaks (as stated previously - LOOK SPECIFICALLY FOR OIL LEAKS - 6.0L are prone to many of these from many possible places!!).
CEL (Check Engine Light) on? No two-ways-about-it -----> GET A CODE READER BEFORE THE PURCHASE and check for DTC's (I suggest ForScan Lite downloaded to a smartphone with the appropriate OBDII adapter - total cost is $40). You can have active DTC’s without a CEL.
The Electronic Shift on the Fly ESOF sometimes fails due to vacuum leaks. Be sure to check this out (several times in and out of 4WD and/or take front wheels off to inspect).
Check for excessive wheel bearing wear (looseness), sway bar (end link looseness), or ball joint looseness. Ball joints and sway bar end links tend to go out in the 70k-90k range. Jack one side up at a time and see if each wheel moves top to bottom only, if so, it is the ball joints. If it moves in all directions then probably wheel bearings.
Check the coolant - if it has the Motorcraft Gold Coolant , it will have to be changed IMO. The Gold coolant tends to gel and form solids when "stressed" or overheated. This can plug up the oil cooler (looking at coolant and oil temperatures will be discussed later as a way to identify a clogged oil cooler) . Look in the "degas" bottle and inspect the fluid - it should be free from solids and there should be NO OIL visible (oil emulsified in water can show up as brown sludge). As previously stated, the degas bottle should not have white residue around the sides of it (possible overheating issues).
Any evidence of a tuner (aftermarket air filter, gauges, etc)? Tuners may or may not be bad. Some tuners are MURDER on the transmission. Some dealerships will cause you a lot of problems w/ them - even if you bought it that way used.
Aftermarket air systems could be a problem. Many of them (like K&N) do not filter as well and could cause issues. Up to 500 hp, the stock air system is best!
Try to find out if the original owner ever ran it empty on fuel or have plugged filters (fuel pressure below 45 psig can damage injectors)? A dealership or a good shop can simulate WOT conditions and test the fuel pressure (IMO it should be 50 psig or above).
Then the common stuff I'm sure you know:
· Look at and smell the fluids. Make sure fluids not burnt, not too thick or dirty. Make sure the oil level is not under-full OR over-full. If it is too high, it could be a sign of diesel in the oil.
· Check the tires - abnormal wear?
· How do the brakes look? Any pads need replacement? Are the rear brakes excessively worn?
· All electronics working? Especially the AC (repair can be expensive)?
· Dents? Air bag been replaced, etc.
· See if he has any repair or maintenance records.
· Take off the price for windshield dings, paint chipped, torn upholstery, etc.
· Does the truck look too clean? Does it look like the oil was just changed? May be hiding something.
· Any extras - tool boxes, bumpers, etc.?
· Drive it - does it hesitate, stutter, or surge? Does it blow white or black smoke? When driving, brake fairly hard - note any pulls, pops, clunks, rattles, etc. How does it accelerate? You should romp on it pretty good. Drive in reverse and then back and forth - listen for clunks.
· Remember, when checking the transmission fluid level, the fluid should be fully warmed up and the truck should be parked on a level surface with the engine running in "park".
Add or subtract value based on condition, high miles, and presence of extras.
Edit:
IMO everyone should have an electronic scan tool BEFORE going to look at a used 6.0L. The cheapest way to go about this is to download either Torque Pro or ForScan Lite to your phone. I find the Torque Pro interface to be better, but ForScan is by far a better code reader. To use these apps, you will need an ELM327 OBDII adapter. I find that the BAFX adapter is very reliable. WiFi works well w/ i-phones and probably also works well w/ Androids (I haven't checked that). BlueTooth works well w/ Android phones. The app and the adapter will cost around $45 total. Very cheap investment for the value you get!!!
The ScanguageII is not a bad tool either. It is around $120, so it is a little more expensive. It is NOT a very good code reader.
The things to look at FIRST - scan for stored codes!!!
After that:
First look at all the temperature readings with your scan tool (do this before attempting to start). They should all be about the same and they should indicate that the engine is cold. That is how you want it when you first look at a 6.0L to buy.
EOT
ECT
TFT
IAT1
IAT2
After verifying that the temperature sensors are correct, look at the pressure sensors:
MAP
Baro
EBP
If you have an 03 or 04, you may have the flash that eliminates the PCM from using the EBP sensor and your scan tool may not pick it up. These pressure sensors shoul all read within about .5 psig of each other w/ the key on and engine off (KOEO).
Then you want to start the truck. It should be a strong AND EVEN crank, and a fairly quick start. You shouldn't see excessive smoke from the exhaust from the start.
When you are starting the truck, you want to watch the following sensors:
ICP pressure, psig
ICP volts
ICP desired, psig
IPR % duty cycle
FICM MPower, volts
FICM LPower, volts
Vehicle voltage
The ICP and IPR information can tell you if you have a strong high-pressure oil system. You want to see ICP get over 500 psig quickly (this will happen around .85 volts on the ICP sensor). You should see the IPR % duty cycle get around 25% or 30% before the start and then when it is idling, it should be 24% to 30% on a cold idle if everything is normal.
04.5 model years and up came with dummy plugs and standpipes that were somewhat leak prone. Over the years, updated parts were provided and they work well.
The 05 and up model years got a new HPOP. It has been very reliable, but the discharge fitting off of this pump was weak. An updated (one-piece) part has solved the problem.
The 03-04.5 HPOP's were weak - period. IMO the only HPOP to install in these model years is a Dieselsite HPOP.
The FICM information can tell you if the FICM power board and FICM supply voltage is good. A healthy "non-modified" FICM should read 47-48 volts at FICM MPower. The LPower is the logic voltage and it should read what the vehicle voltage is.
When cranking, you might drop into the low "10.something voltage", but it should quickly start climbing and should be 13.8 to 14.4 volts when the glow plugs turn off. That said, STRONG batteries can maintain 11 volts or above at crank. Be aware that the glow plug light is NOT indicative of the glow plug operation. The glow plugs will run longer than the light is on. How long depends on how cold it is outside. They can run up to two minutes in cold weather.
Run the truck through it's paces on the test drive, but no hard accelerations until it is fully warmed up. It will take a good 20 minutes to fully warm up.
After fully warmed up, make sure the truck has good acceleration and no hesitation's when accelerating. Look for excessive smoke on accelerations.
After the engine is fully warmed up, look for a healthy oil cooler. Monitor the following:
EOT
ECT
TFT
Make sure that the oil temperature is less than 15 degrees higher than the coolant temperature when driving at steady highway speeds. IMO it should be less than 10 degrees. Make sure that the transmission temperature is not excessive. It should be around 140-150 degrees. The coolant temperature may vary somewhat, but it should stay between 192 and 200 degrees when the engine is not being worked hard.
Monitor the following when driving. Note that the ICP pressure ACTUAL should be maintained pretty close to the ICP DESIRED:
ICP pressure, psig
ICP desired, psig
Check out the engine operation without the A/C, and then with the A/C. Keep an eye on coolant temperatures after turning the A/C on.
Check the heater out - make sure it works.
Check out the steering, Should not be sloppy and the steering wheel should be straight when going straight (and not "wander" when you let go of the steering wheel on a straight-away).
Pay attention to the suspension when hitting bumps.
Check out the braking and make sure the truck doesn't pull to one side when braking. You shouldn't hear any loud squeals either when braking.
After the test drive, shut down the truck. Then re-start the truck. It is important to test out the hot-starts on a 6.0L.
Look at the following on a hot-start:
ICP pressure, psia
ICP voltage
IPR % duty cycle.
The ICP should still quickly get over 500 psig and the engine should start. Starting should occur in less than 3 seconds of cranking IMO. IIRC Ford specification is higher than that. The IPR % duty cycle at idle when hot should be around 26-28 %.
EDIT - More detail on buying a used 6.0L
The reason it is VERY VERY important to get a cold engine to start is because some people might try to hide a cold start problem (which could be a FICM issue or injector issue) by warming it up before you get there.
Before you give it a test drive, open the hood and inspect the coolant system. Put your hand on the radiator, the upper radiator hose, and the side of the degas bottle - the coolant should be cold. Verify that the coolant level is between the min and the max levels as shown by the sticker on the degas bottle. Ford specified that the correct cold level for the coolant is at the minimum mark. You can even remove the degas bottle cap (do so carefully, but it isn't as dangerous as a radiator cap when the coolant is at a proper level in the degas bottle). If there is a lot of residual pressure relieved from the degas bottle when the cap is removed, this is a potential sign of head gasket issues.
While you are looking at the coolant - check out the color of the coolant. A gold color coolant can potentially be the Ford OEM coolant. This coolant is not very robust and can not handle excessive temperatures, mixing w/ other coolants, or exposure to combustion gasses (if there is a head gasket leak or an EGR cooler leak). This coolant is responsible for the bulk of the problems with the oil cooler plugging up. Excessively plugged oil coolers can cause EGR cooler failures AND the oil cooler itself can rupture. When an oil cooler ruptures, it will put oil into the coolant. So verify there isn't ANY contamination of the coolant when you inspect the degas bottle. Make sure there are no white spots around the degas bottle or on the cap. This can be a sign of excessive pressure in the coolant system which can be caused by an EGR cooler leak or head gasket leaks. Some folks have found that the Gold coolant works OK if the engine is never overheated and if it hasn't been contaminated. Also, Ford specifies that it should be changed every 40k miles or it could start degrading (this can cause oil cooler plugging). Green coolant certainly isn't recommended either. It requires fairly frequent addition of chemicals to maintain its corrosion protection. The Gold or Green coolants should be flushed out as quickly as possible if you buy the truck. You want to put in an EC-1 rated ELC coolant. They are usually red.
Regarding the hot start test (which is also VERY important): The 2004.5 and up year models have a few more potential leak issues in the high pressure oil system than the earlier model years. These can cause hard no-starts. Often times, these initially show up when the engine (oil) is fully hot. The 05 and up model years introduced one more potential leak point in the high pressure oil system with the HPOP discharge "STC" (snap-to-connect) fitting. Fortunately the 05 and up HPOP is pretty darn reliable (and it is far from that for the 03, 04, and 04.5)!!
My personal preference is to go for a 2006 or 2007 year model (but really ANY year model low-mileage 6.0L might be worth looking at) - folks WILL DEFINITELY bargain with you. I think that buying a used 6.0L can turn out to be a good deal - if you are wise about the pre-purchase inspection! If you find a good price AND you have checked into the reputation of a local independent shop or dealership on repairing the 6.0L (or if you can do repairs and upgrades yourself) - then GO FOR IT! So much depends on having a competent and honest dealership, a trustworthy independent shop, or personal mechanic skills to troubleshoot and work on any POTENTIAL future problems.
Edit:
IMO everyone should have an electronic scan tool BEFORE going to look at a used 6.0L. The cheapest way to go about this is to download either Torque Pro or ForScan Lite to your phone. I find the Torque Pro interface to be better, but ForScan is by far a better code reader. To use these apps, you will need an ELM327 OBDII adapter. I find that the BAFX adapter is very reliable. WiFi works well w/ i-phones and probably also works well w/ Androids (I haven't checked that). BlueTooth works well w/ Android phones. The app and the adapter will cost around $45 total. Very cheap investment for the value you get!!! A little more on this topic later in the thread!
If you are looking at used 6.0's here are a few considerations (along w/ the CARFAX reports).
Some 6.0L weak points (things to check):
Look for signs of coolant degas bottle overflow (dry white residue on and around the degas bottle or no level in degas bottle).
Lots of idling can cause EGR problems. The 2005 and up model years have engine hours as a possible display. I would look at the hours on the engine (if it has this monitored) and divide the miles by the hours (is it below 25? If so, may have had lots of idling).
Even without much extended idling EGR valves can plug quickly (if it is still stock). In fact, if it is still stock, I would negotiate to pull the EGR valve to inspect it (have them show it to you when it is out and then you need to look into the intake). Check for wetness (w/ rear end jacked up or the truck parked on a "decline") and for excess soot. Wetness could indicate an EGR cooler leak that is common w/ 04.5 and up model years (it could also be excess fuel and indicate injector and/or combustion problems). If the valve is gunked up, have them replace the valve. If the intake is real bad, you may push them to clean it as well.
Look underneath for oil leaks - some trucks have had a lot of them.
Try to find out about the routine maintenance:
· Filter change intervals on time? What kind of oil has been used? (needs to be CI 4 + or CJ 4 rated, and now CK is the rating). Synthetic or conventional oil? 15W40? 5W40? 10W30? IMO synthetic 5W40 or a quality 10W30 is best.
· OEM filters? Look at them and see what kind they are. Aftermarket filters can cause MAJOR problems. A tall oil filter cap is a tell tale sign that the owner didn't really know how to care for the truck properly. A tall cap and an OEM filter can result in low oil pressure and unfiltered oil. WIX filter/cap combination has been the main issue - usually when someone re-used the cap.
· Find proof of Transmission being flushed/changed - it is recommended every 30,000 miles.
· Any exhaust problems visible (i.e. lots of white or blue smoke)? White smoke may mean an EGR cooler leak if the smoke smells like coolant or a sign of injector issues if the smoke smells like fuel.
Check for any FLUID leaks (as stated previously - LOOK SPECIFICALLY FOR OIL LEAKS - 6.0L are prone to many of these from many possible places!!).
CEL (Check Engine Light) on? No two-ways-about-it -----> GET A CODE READER BEFORE THE PURCHASE and check for DTC's (I suggest ForScan Lite downloaded to a smartphone with the appropriate OBDII adapter - total cost is $40). You can have active DTC’s without a CEL.
The Electronic Shift on the Fly ESOF sometimes fails due to vacuum leaks. Be sure to check this out (several times in and out of 4WD and/or take front wheels off to inspect).
Check for excessive wheel bearing wear (looseness), sway bar (end link looseness), or ball joint looseness. Ball joints and sway bar end links tend to go out in the 70k-90k range. Jack one side up at a time and see if each wheel moves top to bottom only, if so, it is the ball joints. If it moves in all directions then probably wheel bearings.
Check the coolant - if it has the Motorcraft Gold Coolant , it will have to be changed IMO. The Gold coolant tends to gel and form solids when "stressed" or overheated. This can plug up the oil cooler (looking at coolant and oil temperatures will be discussed later as a way to identify a clogged oil cooler) . Look in the "degas" bottle and inspect the fluid - it should be free from solids and there should be NO OIL visible (oil emulsified in water can show up as brown sludge). As previously stated, the degas bottle should not have white residue around the sides of it (possible overheating issues).
Any evidence of a tuner (aftermarket air filter, gauges, etc)? Tuners may or may not be bad. Some tuners are MURDER on the transmission. Some dealerships will cause you a lot of problems w/ them - even if you bought it that way used.
Aftermarket air systems could be a problem. Many of them (like K&N) do not filter as well and could cause issues. Up to 500 hp, the stock air system is best!
Try to find out if the original owner ever ran it empty on fuel or have plugged filters (fuel pressure below 45 psig can damage injectors)? A dealership or a good shop can simulate WOT conditions and test the fuel pressure (IMO it should be 50 psig or above).
Then the common stuff I'm sure you know:
· Look at and smell the fluids. Make sure fluids not burnt, not too thick or dirty. Make sure the oil level is not under-full OR over-full. If it is too high, it could be a sign of diesel in the oil.
· Check the tires - abnormal wear?
· How do the brakes look? Any pads need replacement? Are the rear brakes excessively worn?
· All electronics working? Especially the AC (repair can be expensive)?
· Dents? Air bag been replaced, etc.
· See if he has any repair or maintenance records.
· Take off the price for windshield dings, paint chipped, torn upholstery, etc.
· Does the truck look too clean? Does it look like the oil was just changed? May be hiding something.
· Any extras - tool boxes, bumpers, etc.?
· Drive it - does it hesitate, stutter, or surge? Does it blow white or black smoke? When driving, brake fairly hard - note any pulls, pops, clunks, rattles, etc. How does it accelerate? You should romp on it pretty good. Drive in reverse and then back and forth - listen for clunks.
· Remember, when checking the transmission fluid level, the fluid should be fully warmed up and the truck should be parked on a level surface with the engine running in "park".
Add or subtract value based on condition, high miles, and presence of extras.
Edit:
IMO everyone should have an electronic scan tool BEFORE going to look at a used 6.0L. The cheapest way to go about this is to download either Torque Pro or ForScan Lite to your phone. I find the Torque Pro interface to be better, but ForScan is by far a better code reader. To use these apps, you will need an ELM327 OBDII adapter. I find that the BAFX adapter is very reliable. WiFi works well w/ i-phones and probably also works well w/ Androids (I haven't checked that). BlueTooth works well w/ Android phones. The app and the adapter will cost around $45 total. Very cheap investment for the value you get!!!
The ScanguageII is not a bad tool either. It is around $120, so it is a little more expensive. It is NOT a very good code reader.
The things to look at FIRST - scan for stored codes!!!
After that:
First look at all the temperature readings with your scan tool (do this before attempting to start). They should all be about the same and they should indicate that the engine is cold. That is how you want it when you first look at a 6.0L to buy.
EOT
ECT
TFT
IAT1
IAT2
After verifying that the temperature sensors are correct, look at the pressure sensors:
MAP
Baro
EBP
If you have an 03 or 04, you may have the flash that eliminates the PCM from using the EBP sensor and your scan tool may not pick it up. These pressure sensors shoul all read within about .5 psig of each other w/ the key on and engine off (KOEO).
Then you want to start the truck. It should be a strong AND EVEN crank, and a fairly quick start. You shouldn't see excessive smoke from the exhaust from the start.
When you are starting the truck, you want to watch the following sensors:
ICP pressure, psig
ICP volts
ICP desired, psig
IPR % duty cycle
FICM MPower, volts
FICM LPower, volts
Vehicle voltage
The ICP and IPR information can tell you if you have a strong high-pressure oil system. You want to see ICP get over 500 psig quickly (this will happen around .85 volts on the ICP sensor). You should see the IPR % duty cycle get around 25% or 30% before the start and then when it is idling, it should be 24% to 30% on a cold idle if everything is normal.
04.5 model years and up came with dummy plugs and standpipes that were somewhat leak prone. Over the years, updated parts were provided and they work well.
The 05 and up model years got a new HPOP. It has been very reliable, but the discharge fitting off of this pump was weak. An updated (one-piece) part has solved the problem.
The 03-04.5 HPOP's were weak - period. IMO the only HPOP to install in these model years is a Dieselsite HPOP.
The FICM information can tell you if the FICM power board and FICM supply voltage is good. A healthy "non-modified" FICM should read 47-48 volts at FICM MPower. The LPower is the logic voltage and it should read what the vehicle voltage is.
When cranking, you might drop into the low "10.something voltage", but it should quickly start climbing and should be 13.8 to 14.4 volts when the glow plugs turn off. That said, STRONG batteries can maintain 11 volts or above at crank. Be aware that the glow plug light is NOT indicative of the glow plug operation. The glow plugs will run longer than the light is on. How long depends on how cold it is outside. They can run up to two minutes in cold weather.
Run the truck through it's paces on the test drive, but no hard accelerations until it is fully warmed up. It will take a good 20 minutes to fully warm up.
After fully warmed up, make sure the truck has good acceleration and no hesitation's when accelerating. Look for excessive smoke on accelerations.
After the engine is fully warmed up, look for a healthy oil cooler. Monitor the following:
EOT
ECT
TFT
Make sure that the oil temperature is less than 15 degrees higher than the coolant temperature when driving at steady highway speeds. IMO it should be less than 10 degrees. Make sure that the transmission temperature is not excessive. It should be around 140-150 degrees. The coolant temperature may vary somewhat, but it should stay between 192 and 200 degrees when the engine is not being worked hard.
Monitor the following when driving. Note that the ICP pressure ACTUAL should be maintained pretty close to the ICP DESIRED:
ICP pressure, psig
ICP desired, psig
Check out the engine operation without the A/C, and then with the A/C. Keep an eye on coolant temperatures after turning the A/C on.
Check the heater out - make sure it works.
Check out the steering, Should not be sloppy and the steering wheel should be straight when going straight (and not "wander" when you let go of the steering wheel on a straight-away).
Pay attention to the suspension when hitting bumps.
Check out the braking and make sure the truck doesn't pull to one side when braking. You shouldn't hear any loud squeals either when braking.
After the test drive, shut down the truck. Then re-start the truck. It is important to test out the hot-starts on a 6.0L.
Look at the following on a hot-start:
ICP pressure, psia
ICP voltage
IPR % duty cycle.
The ICP should still quickly get over 500 psig and the engine should start. Starting should occur in less than 3 seconds of cranking IMO. IIRC Ford specification is higher than that. The IPR % duty cycle at idle when hot should be around 26-28 %.
EDIT - More detail on buying a used 6.0L
The reason it is VERY VERY important to get a cold engine to start is because some people might try to hide a cold start problem (which could be a FICM issue or injector issue) by warming it up before you get there.
Before you give it a test drive, open the hood and inspect the coolant system. Put your hand on the radiator, the upper radiator hose, and the side of the degas bottle - the coolant should be cold. Verify that the coolant level is between the min and the max levels as shown by the sticker on the degas bottle. Ford specified that the correct cold level for the coolant is at the minimum mark. You can even remove the degas bottle cap (do so carefully, but it isn't as dangerous as a radiator cap when the coolant is at a proper level in the degas bottle). If there is a lot of residual pressure relieved from the degas bottle when the cap is removed, this is a potential sign of head gasket issues.
While you are looking at the coolant - check out the color of the coolant. A gold color coolant can potentially be the Ford OEM coolant. This coolant is not very robust and can not handle excessive temperatures, mixing w/ other coolants, or exposure to combustion gasses (if there is a head gasket leak or an EGR cooler leak). This coolant is responsible for the bulk of the problems with the oil cooler plugging up. Excessively plugged oil coolers can cause EGR cooler failures AND the oil cooler itself can rupture. When an oil cooler ruptures, it will put oil into the coolant. So verify there isn't ANY contamination of the coolant when you inspect the degas bottle. Make sure there are no white spots around the degas bottle or on the cap. This can be a sign of excessive pressure in the coolant system which can be caused by an EGR cooler leak or head gasket leaks. Some folks have found that the Gold coolant works OK if the engine is never overheated and if it hasn't been contaminated. Also, Ford specifies that it should be changed every 40k miles or it could start degrading (this can cause oil cooler plugging). Green coolant certainly isn't recommended either. It requires fairly frequent addition of chemicals to maintain its corrosion protection. The Gold or Green coolants should be flushed out as quickly as possible if you buy the truck. You want to put in an EC-1 rated ELC coolant. They are usually red.
Regarding the hot start test (which is also VERY important): The 2004.5 and up year models have a few more potential leak issues in the high pressure oil system than the earlier model years. These can cause hard no-starts. Often times, these initially show up when the engine (oil) is fully hot. The 05 and up model years introduced one more potential leak point in the high pressure oil system with the HPOP discharge "STC" (snap-to-connect) fitting. Fortunately the 05 and up HPOP is pretty darn reliable (and it is far from that for the 03, 04, and 04.5)!!