Check the laws in your state regarding loans...some states that are community property states...unless you have a LEGAL seperation you are equally responsible for all debts aquired by either of you...meaning that just because he did it without you (or as in my case, without my even knowing) does not excuse you from the debt collectors...
A LEGAL seperation will protect you...if your state has that, if not I would contact an attorney asap and stop him from buying the car if you can...unless of course you want a new car down the road?
I haven't been around much because one of my best friends and my rock when my H went through his MLC just told me over a week ago that her H walked out...they have 3 boys...I have been helping her