Hello, I work as a mechanic for a company that have some Hino trucks, they are less than 300 000 miles, 2007 - 2011 and 2 of them have a coolant or oil or both leaking in the motor head, behind the turbo, almost impossible to see but the driver listen a sound that show that the motor is loosing water, when i check the water tank, it is real the water is under the level.Two images are attached
My question is: where or what do you think this leaking is coming???
Thanks for your help
It's the head gasket. This is the most common form of head gasket leak on these. Externally, right rear of engine, right in front of the nook. Sometimes behind the turbo.
The head gasket has been updated to prevent oil leakage from occurring.
Do not have the head machined. There is no provision for adjusting tooth clearance on the idler gear.
There are a list of parts that must be replaced if you go in after the head gasket. The injector fuel return line, the special banjo bolt from the return line to the rocker box, the seal washers for this special bolt and the six injector banjo bolts, the six injector hold down bolts. Consider replacing the rocker shaft bolts, they have been redesigned.
You will probably find rust right next to the sealing surface of the injection lines. If this is happening, or the lines look like they've been overtightened, replace them. I'd consider replacing all six injector cups. They're around $50 each. With the head off you can install the new ones using a very simple tool. With the head on the truck, special tools are required.
Most importantly,the injector fuel return line has to be installed a specific way, within a specific sequence of installing other stuff to ensure that it does not get damaged. Damaging this by bending or kinking it is going to end badly.
Now is the perfect time to reseal the oil cooler. That's probably barfing various fluids too. If it's not, it will soon enough. It's simple, three 'd' rings and sealant.
No special tools are needed, aside from a 1/4" drive torque wrench that can accurately measure 100-115 lb/in, another that reads between 10-50 lb/ft, a 17mm 12pt socket, a cherry picker, a paint marker, a cummins injector line socket (optional)and an 8mm ball bearing (I'd have to double check that since I have the injector cup tool ).
You're probably going to break a couple of bolts on the exhaust. Do yourself a favor and just pay whatever the machine shop wants to drill them out/ helicoil/whatever. Spending three hours drilling out hard stainless hardware sucks pretty hardcore.
