Hi
I dont think that its possible to test the routers, b'coz most probably, ur service provider must have implemented HSRP. So, in case of failure, that same ip would be continued to be in use. Hence there wont be any change seen as far as users are concerned.
Also u do not have the access to the routers, which makes it more difficult to give suggestions. In any case, it would be difficult to troubleshoot what happening, and u will end up nowhere.So do not think of this.
One thing u can do without affecting ur current setup is to pull out the ethernet cable of secondary router from the 4507 and attach it directly to the PC and see. Make sure u give proper IP address on to ur PC.But I doubt this will work, if u have enabled routing onto that 4507.
I cant think of any other way .The only way remains is te "brutual" way.
Regards
JD