Repeat Coolant Leak-EGR and cylinders?

[ChelseyV]

Hoping to get some mechanical advice. I own a new to me 2015 fleetwood Discovery 40g with 62k miles on it. Prior owner had a coolant leak at 58k miles. Replaced EGR cooler, didn’t fix leak. Took to Cummins shop and replaced 30 caps in head due to leak. 4,000 miles later we drive it and get white exhaust with low coolant alarm. First shop can’t find a leak but notices lash valve is out of spec. They fix it and Cummins sends us on our way. 100 miles off of the service lot, we get a repeat low coolant alarm. New shop finds crack in EGR cooler and wants to replace cylinders due to #4-6 cleaned from coolant leak. Mechanic at first says that he found physical leak in cylinders but after asking him to demonstrate it, he claims we won’t be able to find a leak with pressure. He is certain that we need to replace cylinders #4-6 because they are clean from coolant leaking inside. Says it is impossible for coolant to back flow from EGR cooler to cylinders. Mechanic invites Cummins rep to take a look and back up his recommendation.

We have a home RV mechanic that calls BS. He advises us to replace EGR cooler with Bulletproof EGR and move along.

If there was a leak in cylinders, shouldn’t a mechanic be able to demonstrate this? Thoughts or advice?

[Ranger Smith]

I am not a diesel mechanic but I think with such high compression that these diesel engines have if there was a cylinder leak it would pressurize the coolant system to the point it would be blowing radiator caps and pouring out the coolant overflow due to the high pressure.

[153stars]

You can do compression and cylinder leak down test. To test cylinders.
A washed out cylinder similar to dusted, hope thats wrong.
You don't hear of many diesels cylinder leaks unless pitting from not maintaining the SCA coolant.