On September 17, 2001, at 1638 eastern daylight time, a Cessna 172R, N158RA, registered to Airline Training Academy, collided with the ground following a loss of engine power. The training flight was operated by the certified flight instructor (CFI) under the provisions of Title 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the accident, and an instrument flight rules (IFR) flight plan was filed for the cross country flight to Ocala, Florida. The CFI and pilot-rated student were not injured, and the airplane sustained substantial damage. The flight originated from Orlando, Florida, at 1515. According to the CFI and the pilot-rated student, the flight was being conducted for the purpose of and evaluation flight for the private pilot's instrument check ride. Both stated that while enroute to Ocala, Florida, they were told to climb to 6,000 feet mean sea level (MSL). Between 5,000 and 6,000 feet MSL they noticed the oil pressure drop to zero and the enunciator began to flicker. The CFI called Orlando approach and informed them of the zero indication of oil pressure and that they wanted to return to Orlando. The CFI stated that the reason he elected to return to Orlando was because there was no change in the oil temperature and there was no roughness in the engine. Orlando approach vectored them to a 180 degree heading and had them descend to 2,000 feet msl. At about 3500 feet msl they began hearing a knocking noise. The CFI contacted approach and declared an emergency. Shortly after that the airplane began to vibrate violently and smoke began pouring into the cockpit, then the engine and propeller stopped, there was no wind milling or movement. Both pilots stated that they had been looking for a place to make a forced landing if necessary and had spotted a field next to the 408 expressway. The expressway was ruled out due to traffic. They made their approach and floated further then they expected. They maneuvered over some small obstacles and impacted the ground and slid until coming to a complete stop. Examination of the engine found the two bottom attachment retention nuts for the upper (left) vacuum pump were loose. Approximately one quart of oil was found in the engine and oil filter. The belly of the airplane was coated with oil from the firewall to the tail mooring point. A hole was found in the engine case above the number four cylinder. The number four connecting rod was broken at the rod cap and exhibited high heat signatures. No anomalies were found with the oil pump or oil lines. A review of the airframe maintenance logbooks revealed that the left vacuum pump and been removed and replaced on the same day of the accident prior to the accident flight. Damage consisted of a collapsed nose and left main landing gear. The fire wall was damaged and the left wing was bent upward approximately two feet inboard from the tip. An oil leak test was performed on another 172R, on September 26, 2001. The two lower nuts of the upper vacuum pump were loosened and the engine was run near full static RPM for five minutes. Oil began leaking from the vacuum pump as soon as the engine was started. After five minutes, the back of the engine, the lower cowling, engine accessories and the ground were partially covered with oil. The amount of oil lost during the test was estimated to be less then one quart. Examination of Cessna pilot operating handbook, Section 3, emergency procedures states in part; Low Oil Pressure, if the low oil pressure enunciator (OIL PRESS) illuminates and oil temperature remains normal, it is possible the oil pressure sending unit or relief valve is malfunctioning. However, land at the nearest airport to inspect the source of trouble.