Check the cooling system, radiators can be a problem, Power steering pump check to see it doesn't whine and fluid is red. Check block/head on right side at the back, if head gasket
leaks coolant that is normally where it starts. Ask if the coolant filter has been removed permanently , there was a service bulletin on that. Check the fuel line grommets where the
fuel lines enter cylinder head {left side} those are common to leak. Check water pump {belt driven left side} those can weep. But most of all ask for paper work/service records
for when the last time the valves and injectors were adjusted {no more than 150,000 miles between adjustments} despite what anyone says. Injectors run $960.00 ea for that engine.
But there are some instances of valve issues with some DD15-DD16 engines {some not all and there is no telling which ones will have a issue and it's not all that common.
Starter is on right side and takes the early style starter 12 tooth IIRC. Air compressor and power steering are located on the left rear of engine at bell housing. The gear train is at
the back of engine. Find out when the last Emissions work was done-if it hasn't had what is called the {1 BOX} replaced} That's big money to replace it $9,000.00. They usually need
the 1BOX replaced around 325,000 miles. Ask if the DEF pump has been changed. Check and see when it had belts and tensioner changed. Plus ask when the coolant hoses to air compressor were changed, those
use a push-lock connection and will start leaking at the drop of a hat. Both are a pain to change, the short
{L shaped one from block to compressor usually leaks first}. The other long one from water pump housing
to compressor likes to start leaking at the support clamps. The originals were made of Black Nylon/Plastic,
and have been upgraded also.
Oil filter #A4731800909 $25.10
Fuel filter kit {contains two} #A4700903151 $59.61
11 gals oil capacity
Air filter could be two choices and can run as high as $246.00
Belt tensioner was upgraded to a Gates #38677-DD does not service the original style tensioner anymore.
AC/alternator belt number {last three digits 496}
Fan drive Belt number {last three digits 635}
Best I can tell you at this point.