I just got a 87 turbo 5 spd the other day that is in very nice condition although rather high miles (160 000) but as i was just checking things out under the hood today i opened up the rad cap and there was kind of rusty water on the inside which leads me to beleive there is maybe a leak where moisture is getting in somewhere? any suggestions? i would also like to know how to do a leakdown test or if you have to take it to a shop to have it done?

Thanks

a leak down test consists of compresing the cylinder and listening to the exhaust and intake valves.if you can hear air comming out of either you have a failure.i would get a compresion tester,pull all plug wires remove one spark plug at a time install compression tester(screw in kind)and crank engine until preasure is at max then simply listen to the exhaust valves for air leaks,then listen to intake vaves for air leaks.

You'd be wasting your time, as that will not work. You must have a pressurized air source and an adaptor to do a 'cylinder leakdown test'.
Perhaps 87supraturbo was refering to a cooling system pressure test. If so, it would be cheaper to have a shop do it, as cost of the tester is not low. Plus a shop can test for a BHG at the same time.