My 87 is constantly leaking antifreeze through the weep hole and seeping into the oil in the case. I replaced all the gaskets put a new impeller and shaft in and it still leaks. I found out that when the quads were new and serviced by a dealer they used bars leak anytime they changed the antifreeze. Could this be my issue? I don't want to add the stuff and have it gum everything up and it not even fix the issue . Any help would be great.

Did you replace your mechanical seal?

Ok well if you did that and by everything you also mean the impeller and shaft then I would have to say your mechanical seal has an issue and you need a new one. You could try that bars stuff but your basically introducing a sealant into your cooling system which I would not recomend. It would be stoping your leak but not your problem. That stuff is a temporary fix and won't last forever. a weep hole is there to tell you you have an issue and you obviously do. If you plug up your weep hole you can run into the issue of your oil seal leaking and then coolant will go into your oil and if your out for a good ride you can overheat and something getting to hot and seizing up. A lot of people don't know but mechanical seals have a shelf life. They don't last forever. So you could of got a bad one or by the looks of what you shared the seals could be a hit or miss thing and mechanics improvised or they could be really hard to get installed without them getting messed up and not working. Take it appart again and be careful when installing it and put a bit of blue thread lock on the outside of the seal. That will help it go in a little easier and will hopefully seal it properly.