Oil leak hi i have a bmw 320ci 2002 and i have an oil leak dripping by the cat i need to replace a pipe but i cant see where it starts and finishes is there a visual diagram availabe

Look in the radiator for the presence of oil or bubbles. See if water is dripping from the tail pipe. All these indicate the engine is burning the coolant. Look for a blown head gasket or a cracked head.

sorry would need to see it to know the problem ,but i have had it where the oil filter itself wasnt made properly and it leaks on the crimped seal on the filter .

No, you should not worry. Tail pipe dripping isn't related to your radiator. It's common especially if your vehicle sits alot.

Small oil leak. You need to find the source of it. Use some good engine degreaser and clean it up. You should then be able to find where it's coming from as you fire it up and check around. I understand sometimes that's hard because things are packed in. How fast are you losing oil? Check the level on your dipstick.

clean the engine and check where it is coming from. Is it at the front of the rear> do you smell burning oil when you switch off the engine? Clean an area under the engine compartment and see where the oil is dripping from and get back to us. Typical places for leaks are the valve cover gasket, oil filter housing bracket.

where does it drip from? could be PAS fluid or gearbox oil so check the common places where they would leak, i.e seals and pipes. cant see why a battery would leak red fluid but might as well check that too

make sure that the filler cap seal is in place and not gone hard over time also has the rocker cover been off at some stage if it has check that the gasket has not moved the other thing to look out for is that the PCV (breather )valve is in good working order if it is damaged the sump compression will rise and push oil out

A fellow BMW enthusiast who has owned many of them once said "Show me a BMW that is not leaking power steering fluid, and I'll show you a BMW with no power steering fluid in it. This problem is common to the point of being universal.
If the oil stain on your garage floor is not annoying you yet, then you don't really NEED to replace the hose yet. All four of my BMWs are at least damp with oil in that area.
That being said, the high pressure hose is actually two hoses that run parallel to each other with a metal U-shaped pipe connecting them together. This assembly will run you $275 at the dealer or $225 on line.

The oil leak is most likely a power steering hose. That is not related to the overheating.
BMWs built in the past 25 years have been notorious for power steering hose leaks. Not a problem. Just an annoyance. One day you get tired of replacing the piece of cardboard that you put on your garage floor, then you replace two or three hoses, and that stops the drip for 5 years or so before it starts leaking again.
When and how does the car overheat? Does it cool down at highway speed or if you turn on the heater? How long after starting the car does it overheat? Are you certain that you bled all the air out of the system when you replaced the reservoir? Does the heater work normally?
BMWs also seem to destroy more than their fair share of thermostats. I drove my Volvo for 20 years on the same thermostat, but I have already replaced the thermostats in both my '97 BMWs.
If you have used BMW coolant and distilled water in the radiator, then the radiator should not be plugged up inside. If you have used hard water or silicate antifreeze, you could have blockage inside.
Radiators can get plugged up outside if they get leaves, lint, pet hair, or other debris in their air fins. I used to have a long haired cat that lived in the garage. It would sleep on the hood and shed. When I would start the car in the morning, handfulls of long cat hair would slide down the hood and get pulled into the radiator by the fan air flow. I had to remove the radiator and clean it out every two years when I replaced the coolant.

oil changes are scheduled by mileage and or days. it appears you have reached the time in which your bmw is due for an oil change

Ok, check the head gaskets for damage and the valve cover gaskets as well. replace any gaskets that are visibly worn. check the oil pressure switch as well. this is a leak spot.