Cummins ISX coolant loss...

2010 is a bad year. But most isx have similar issues.
It could be a head gasket, or egr cooler, or liner issue, or perhaps a DEF injector.
@Justrucking2 can give you some pointers to look at.

 

They have updated the cylinder with APR kit.
And the emissions system is on recall right now.

 

While there is no direct campaigns that would apply to your complaint of coolant loss, the egr cooler is the most likely culprit. If you provide a good engine serial number we can see exactly what you have and can key in on tsb's that pertain directly to your engine in question.

You can also search yourself with a free trial on QSOL.

Cummins Inc. :: QuickServe Online

 

Two gallons is a lot. If it's going in the crankcase or exhaust they are ruining the engine.

F the bulletins, and Internet, take it to Cummins or a shop, before the engine is toast.

 

If the head gasket isn’t the fail and the egr cooler failed the leak test then I don’t know why the are trying to sell you liners and a head gasket, unless the motor hydro locked. That’s a big job on an isx. Radiator has to be pulled, cams get pulled out, head has to come off, oil pan gets pulled, the pistons get pulled, your looking possibly at cutting counterbores, replacing a head. Rebuilding the motor at that point.

If the egr cooler is failing the leak test then I think they’re trying to sell y’all on a big job. Idk... idk If that internal coolant loss has caused internal damage though. If it hasn’t hydrolocked yet it could still be good maybe. They should of pressure tested it with the oil pan off to watch for coolant coming down the liners

 

First... find out if leak is internal or external. If external it could be blowing out the serge tank (rad cap). That's usually BAD. You have compression inside your coolant system. Usually a blow head-gasket, dropped cylinder liner, or cracked head (over-heated). In rare cases, the fault is in the turbo or the air compressor (but very rare). You will also have signs of oil/coolant cross-contamination. Look for oil in coolant and vise-versa. If you have the original EGR cooler (usually still painted red) and no external signs of leaks, look at your exhaust. It will be white and smell sweet like coolant.(this can also be the above mentioned as well) Unfortunately, any coolant loss, other than an external leaking hose/pipe/radiator is usually very bad news for your engine. If it just started losing coolant, stop driving it immediately and get into a certified Cummins repair facility. The longer you drive in this condition, the more you risk extensive internal damage. Sign on to Cummins Quickserve.com (you'll need engine serial #) and you can find out just about anything there.
Hope this helps.
p.s. A member here called Heavyd, is extremely familiar with Cummins engines.

 

EGR coolers are 100% failure. Head gaskets usually cause compression/pressure in the cooling system and push coolant out of the reservoir. I highly doubt you need a head gasket and liners.