Hi, I installed few HHO systems on some cars, and here are damages (so far):

1. On one 3.0 turbo diesel (180PSI) foam from hho enetr into turbo charger an destroy it.

2. On one turbo diesel vapour from HHO gas destroy intercooler - it made holes on it like swiss cheese from Tom&Jerry.

3. On MB 2.7 CDI (170PSI) HHO was detonating in intake just before entering the engine (probably by fire entering from exhaust by EGR) and blow of plastic intake with holes like granate...

not to mention than once drop from electrolyte (KOH) went in my eye and I still can not recover from burn .....
Everyone of your mentioned problems has happened because of either a poor system that does not have the correct safety systems, wrong amount of HHO being injected, or poor or non existent filtering system. If anyone would spend enough time studying the many posts on this forum they would have discovered many warnings and many different solutions to most of the problems.

The biggest problem with HHO is the very poor systems that are being sold or made in someones back yard by people who have no idea what happens long term or with irresponsible people just slopping on a system without the proper filters or safety mechanisms. HHO is not something one should get involved in until you understand all the ramifications and how thing work. Plan to spend some real money to get something that is safe and really works. One had better know exactly what he is doing or you will not get any gains and or possibility cause some damage to your engine.

Continual maintenance is also left out of most sales pitches. This is much more involved than you think and if not done regularly you will have many of the above problems or declining positive results, or just no positive results.

When done correctly it is as safe as the fuel in your tank and will cause no damage to the engine. It will in fact help keep the carbon build up to a minimum, while cleaning out the excessive carbon build up over time. It will also give you a cleaner exhaust.