A warning about Evans Waterless Coolants

1967 'cuda said
Phreakish, I've rebuilt a few motors that had had their antifreeze changed regularly and there was quite a bit of crud in the water passages. - Enough to have probably been a concern. I doubt that distilled water was mixed with the coolant though. Are you saying that the buildup was due to tap water? - Or was it due to the antifreeze breaking down? And on the subject of antifreeze, are some brands more likely to cause problems than others?

Tap water, old antifreeze, mixing different brands, using flushes or stop leaks can all cause this kind of buildup. Most antifreeze has corrosion inhibitors, but they breakdown just like anything else. When they do, or when different brands are mixed (which might use different packages) it can cause the 'gum' we know and hate. They'll break down sooner in the presence of anything that's not pure water. I'd also wonder why the engines were rebuilt - any internal failure which can cause coolant and combustion gasses or oil to mix will wreak havoc inside the cooling system in short order.

There's also the electrolysis issue. Bad groundings, lack of grounding, attaching ground straps where convenient rather than where intended. All can cause even 'good' coolant to show issues. Water isn't the fault here, though a more dielectric coolant might stave off the issue, the real problem is a poor electrical system. This is a problem on many hot rods and home-built cars because it's simply not understood. Electric potential in the cooling system will corrode parts no matter how many inhibitors are present. Minerals and contamination in the added water will accelerate it.

All coolants have their drawbacks and benefits. The only one I've seen regular issues with was Dexcool. The 'crud' tended to float rather than sink, and as a result collected around gaskets and the like. It also doesn't like being mixed with air, so cars that were ever run until an air pocket formed in their reservoirs tended to have major issues in the cooling system. It was also a lot more sensitive to non-clean water based on my experiences. But still, regular maintenance and pure water seemed to reduce issues substantially.