Regular Contributor

Re: "Black Coolant" in a 3520

For cleaning oil / sludge from the Cooling system the only product Cat suggest or recommend is non foaming dishwashing detergent such as that used in dishwashing machines. However this type of detergent is relatively benign and in the case of oil cooler failures for example it can take several attempts and hours of engine operation to obtain a satisfactory result. I have seen more aggressive detergents used with good results but this also risks damage to cooling system seals due to compatablity issues, worst case damage to cylinder liner seals and head gasket water ferrules. Suggest you obtain a chemical analysis of the material to determine what it is and how to prevent further production and then what would be the most effective way of removing it.

New member

"Black Coolant" in a 3520

We have a 3520c on LFG that is up for emissions check in a month. What we titled "Black coolant", it is a black gel (cholesterol if you will) that plugs up the piping and passages. Now the only way to truly rid the engine of this is a Major overhaul and a lot of elbow grease because it will come back if there is any trace of it left. My question is, has anyone has run into this and has tried any flushing or cleaning product that has somewhat worked? I just need to get another 250kW out of the engine for testing purposes without overheating.