HelloCustomer You can try anything, I have never had success with those treatments. I would suggest a replacement engine to avoid spending money that will not bring you longevity. Have had to replace the headgaskets twice, i would abandon that engine in favor of another. A rebuilt would be a better option, many companies offer fantastic warranties around the 3 year 100000 mile range. It is more, but you can get the time out of it. You definately can try the products, if they give you a permanent repair or time, it's worth the effort. Just make sure their product will not hurt your heatercore, because that is a byproduct of some of the products.
Your JA Expert,
How much would it cost (ball park) to install a replaement engine cost for this van?