BMW Repair: 1994 325is starting problem, oil filler cap, connecting rod bearings

Question
My son just rode 9 hours from Florida to North Carolina. It rained the whole  9 hours. He had no problems while on the road. He started to drive the car after it had been sitting for maybe 6 hours. he got to the top of a hill and the car cut  off. When he restarted the computer showed check coolant level and cut off. He added fluid and the car started , but cut off again. He said he could smell gas and he had a back fire, plus he said the engine was making a noise. Can you help?

Answer
Hi Mark!
The engine has overheated due to lack of coolant.
First, open your radiator cap and see if there is oil mixed with the water or if you see any oil in there. Remove the oil filler cap and look inside to see if there is some sort of whitish emulsion which is a sign that water has mixed with the oil. Look for the same in the oil dipstick.
If there is a mixing of the two (oil and water), then the cylinder head must be removed and checked for cracks or warpage, if none, re-install with a new head gasket.
If there is no mixing of oil and water
then make sure that the coolant level is really OK. Remove the bleeder screw on top of the expansion tank of the radiator (beside the radiator cap) and fill up with water to the top of the filler neck. Put back the bleeder screw, but not the cap, start engine if it would start, rev up to 1500, see if there is water spewing out of the side of the expansion tank, then refill again to the neck, then close cap. Run engine at idling and turn on the heater for a minute. Now your coolant level is OK.
If when you run the engine, there is a noise in front of the engine, the least damage you can expect is a heat-damaged timing chain, chain guides and tensioner.
If there is  noise from the top of the engine, it is either the valves, camshaft bushings or the piston rings.
If there is hard knocking, it could be the piston pins or worst case scenario, connecting rod bearings or main bearings.
The smell of gas could be due to any number of things. Change of timing due to damage to timing chain or valves.
Damage to electronic parts due to overheating (coils, cam sensors, etc).. A good scan tool can tell you some more things as to how your engine stands.
I would suggest that you bring it to a good mechanic. This kind of engine does not necessarily have to be brought to a dealer since it does not have variable timing.
Tino