Do military jets' radar jammers block their own radar? And, if not, why not?
If you are emitting RF, you can be seen.  There are two ways to emit RF: 1. Transmit (or leak) a RF signal, and 2. Reflect a RF signal.

A jamming device emits (usually) high amounts of RF, with the general idea that the receiver of someone's radar unit will be desensed or otherwise overwhelmed by the signal.  Like putting a multicolored sun into a small dark room.  

So with multiple receivers (as in multi-static radar) a jamming aircraft can normally be rather precisely located (assuming omnidirectional uniformity of the jamming signal). 

When noise jamming, your aircraft may not broadcast on, near or on harmonics of a given frequency within a temporal frame of when you are emitting on that frequency, so your receiver has the opportunity to detect returns. More importantly, your noise emitter may drop power and your radar receiver may have cans (well, cavities) tuned to protect the sensitivity of your radar receiver when expecting a return signal.

There are many books on radar technology, but I believe EW102 covers radar, deceptions, noise jammers and other techniques in a manner that most mildly technical people can read and understand.  There are other books, but I use that series in an Electronic Warfare course I teach, and they are reasonably current. The open literature is rich with advances in jamming and other stealth methodologies that have advanced tremendously in the last 50 years.