what do i need to buy to do a leak down test? or how much do garages charge?
i found info on compression tests, but none on leak down tests.

 

This link will give you some information: http://www.xs11.com/tips/misc/misc3.shtml .

The diagram shows a single gauge tester. Dual gauge units are preferred. A dual guage unit will have guages on both sides of the restrictor.

Autor parts houses, or specialty tool outlets should be able to supply you with a single or a dual gauge tester.