coolant question

ok so i know iam not a certified mechanic or anything but this one blew me away when i got told it. my mother inlaw is having problems with her radiator leaking, she asked what coolant to use and i told her the best thing would be to get the 50/50 mix that way she doesnt have to worry about mixing it, this is in a older dodge caravan with the v6 by the way, she asked what about the leak and i told her that they make a stop leak she can put in there that will take care of small leaks but nothing major, well as the story goes she asked a family friend who is supposed to be a certified ASE mechanic what to do, he tells her to buy a different stop leak that doesnt work, then tells her oh well you need to get a new radiator, then tells her she needs to run straight antifreeze in it, she does what he says and low and behold blows the radiator, is there some thing that i missed here shouldnt you know what your talking about when you are certified as a mechanic and he is that manager of a shop. what the hell even my wife knows you dont run straight antifreeze in a car, now the mother in law needs a new radiator and i wont let her take it to him, theres not really a question in here i just wanted some input on this, it is really bugging me that this idiot is a certified mechanic telling people to do things like this...

You said it when you said he is the "Manager". He may not have any idea what the machanics are doing anymore. Or he may have done this to get more work into his shop.

As bad as the mgrs advise may have been, it is probable that the radiator was ready to let loose anyway. If all it took was to put some undiluted coolant in there, then I'm guessing that there wasn't much life left in it. How much coolant did she have to put in? Are you able to swap out the old radiator for her? Shouldn't be too difficult to do. I wouldn't take it back to that shop though.

She had put it in after the radiator dumped all the coolant out. She had put just water in first and after that leaked out she put the stop leak in and then the straight antifreeze and then it went to radiator heaven im going to look at it today and see if I can do it for her

ALL stop leak is garbage if it plugs a hole in the radiator it will stop the whole thing up to then it will blow the radiator 50/50 is half antifreeze and half water you have to fill the whole system up with 50/50 straight antifreeze is 1 bottle then fill up with water no special mixing