One problem related to crankcase (pcv) has been reported for the 1996 Honda Odyssey. The most recently reported issues are listed below.
The counter balance shaft seal on the engine "popped out". This drained all of the engine oil out of the crankcase. In researching this on the NHTSA web site I have seen a lot of Honda accords with the same problem (same 4 cylinder engine). When I called the local Honda dealer over the phone with the symptoms he correctly diagnosed the problem (they fixed the popped out seal, belts, labor etc) over the phone as he had seen this several times. He goes so far as to recommend that this $5 seal be changed on a routine maintenance checkup. This was a catastrophic failure and this could have been much worse in property damage and personal injury damage. The counterbalance shaft was added to stabilize the four cylinder vibration but the fix is much more of a problem. This engine is not a good design. I tried to get Honda to answer how often this should occur as I know that some failures will occur. They would not let me talk with an engineer and I merely talked with a customer service rep. They do not feel like this is a problem but from what I can find on the net it is happening much more than Honda will admit. Please follow up with Honda on this for me. Thanks.