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Hey guys I've got an isx15 2350 mandated and about 2 months ago I popped a radiator cap. I replaced it and have been keeping an eye on it. The last time after blowing the first cap I had to add coolant and then I was having def quality derate so I changed my def level sensor assembly. I ended up removing my def heater coil so I disconnected the coolant lines to do this and lost coolant about 3 weeks ago. That's the only time from popping my cap the first time 2 months ago that I added coolant. My overflow side of my coolant tank has a small amount of coolant in it. Truck has 335k miles 2015 t800. I hope it's not the head. I can't afford an 8k head right now.
I drive the way rawze preaches but do not have a Pyro gage. Truck is showing 7.7mpg and it's historically been within .2mpg. Half of all my miles are empty while the other half are 80k gross. When I bought this truck I was getting 4.9-5.3 mpg. Nox sensors dpf filter doser injector and I'm starting to get good mpg. I wouldn't be left standing without the help of rawze and everyone here that shares your knowledge and experience.

You might have dropped a liner. You could try a block test kit

Block Tester BT-500 Combustion Leak Test Kit - Made in USA https://a.co/d/3rsUSNJ

It looks for combustion gases in the coolant. It's not the most reliable way to test but is probably the fastest and easiest.

I really hope not, I'll order that now. My head is spinning.

Most auto parts stores sell those kits, just an FYI. I bought mine at my local NAPA.

Got it in hand. Gotta figure out how to do the test. Thanks

(12-08-2022 )FnG92 Wrote: [ -> ]Got it in hand. Gotta figure out how to do the test. Thanks

Get the motor hot! Idle the motor, and bump the rpm with the cruise, you want the thermostat to open. I try to get the motor to 200* + on the water temp side. That way the test should work. It may take up to an hour, depending on outdoor temps.

I bought a kit asking for a vacuum, I might need to return it and find another. Hypothetically the test is negative, where would the experts look next?

If you are indeed getting too much pressure in your cooling system, it can only be 2 things. One is a dropped liner (most common) the other place it could come from is the air compressor (not likely but not impossible) So first you really need to establish if your cooling system is overpressurized or not. Blowing caps off seems like a red flag to me but I'm not there and don't know the dynamics of your whole situation.

Yes sir, run the test kit and if it's negative I'll check the outlet line on the compressor for moisture/coolant?