Auto problems...used dealership

I bought a truck from a used car dealership in Colorado 2 months ago. The truck started over heating about a couple days ago. When I went to put coolant in the truck I noticed a very think, greasy substance in my reserve tank. I found out the substance is call "stop leak."
I believe that there was a leak in the radiator when the machanics at the dealership inspected the truck, and put the "stop leak" in there as a quick fix. Is that legal? Or should they have given me a new/ or fixed my radiator.
Or if the previous owner put the "stop leak" in the radiator, should the dealership of flushed it out, and solved the problem another way.
I do not have a warrenty on the truck.
Please help me.

Lauren Boebert
Boebert1024@aol.com

If they purpoely hid that from you then based on what you say here, you could file suit against them (or at least threaten to do so) in small claims court or in regular court; filing in small claims court is easier and requires no attorney...you could try to collect all of the costs and damages that you suffered due to their behavior... You may also report them to your state attorney general's office.

If I want them to pay to fix my truck, should I get it fixed first and have them reimberse me? Or should I have them pay for the truck when it is fixed.

Also...I found out that it was not "stop leak" used in my radiator. It is the EGR Cooler. It went out and is leaking a gray "mud" through out everything under the hood....engine, radiator, hoses...etc. So really that just makes everything worse. That is a lot more to fix/replace than just a leaky radiator.