Leaking oil My car has been leaking oil but only seems to leak under hot temps., I had changed the oil recently, hoping it was just bad oil, continued to leak so i removed a cover to the rear main seal, it hasn't seemed to leak in a while, Is it possible the leaking oil was only coming from the cover or do I have a serious issue?

I would be checking the radiator closely to determine where the leak is.

Smoke (blue or black) or steam (white)? White smoke is really steam that is caused by water leaking onto hot surface. Could be leaking from hose running to heater coil under dash, or something else. Check radiator water level to make sure water level is ok. Blue smoke is oil burning. This could be dangerous, caused by similar scenario of oil leaking on a hot surface (from a gasket leak, etc), or exhaust fumes. Black smoke means something is actually burning and could indicate fire. Black or blue some could fill vehicle cabin with toxic fumes, even if you don't smell anything bad.

Frost plug, water pump leaking?

It very well may be comeing from under the engine, sounds like there is an oil leak that only leaks under presure and is leaking on to the hot exhast.

You should look under the car after it sits a while and see if there is antifreeze on the ground. If so try to see where it could be leaking under the hood directly over the puddle. You could have a leaking water pump. If so there would be dampness under the right side of engine compartment. Also check the radiator hoses at front of car.

There can be alot of causes, such as valve covers leaking, oil pan gasket leaking, oil filter leaking, rear main seal leaking, front timing chain cover seal or gasket leaking even bad rings. Does it smoke out of the back? Your valve seals could be leaking. Best way to find out if you have a leak is to inspect the valve covers manually, or take newspapers and lay them under the entire engine on the ground, and it will leave the tell tale stain of a leak. Hope this helps.

SMOKE UNDER HOOD COULD BE COOLANT LEAK FROM RADIATOR ITSELF OR CHECK FOR LEAKING TOP RADIATOR HOSE AND CHECK FOR LEAKING BOTTOM RADIATOR HOSE.LOOK UNDER THE HOOD IF COOLANT BOILING OUT COOLANT OVERFLOW JUG ENGINE OVERHEATING FROM BAD THERMOSTAT OR BAD WATER PUMP.CHECK FOR COOLANT LEAK AT WATER PUMP WEEP HOLE.IF SO WATER PUMP NEED REPLACING.ADD MORE COOLANT UNTIL LEVEL CORRECT.TRY LOCATE LEAK. IF CAR OVERHEATED AND BOILED IT OUT. SMOKE UNDER THE HOOD CAN ALSO BE CAUSED BY LEAKING VALVE COVERS WHICH CAN BE FIRE HAZARD IF OIL LEAKS ON HOT EXHAUST MANIFOLD.

Oil leak will not change run temp but can cause a fire.
The smoke is the oil burning on the engine. The 1st thing you need to do is clean the oil off the engine.
Next top oil off to the full line on the dip stick.Now start the engine hold idle up to around 1600 rpm for 1 to 2 minutes keep engine run and look for the oil leak. Don't get caught in any moving parts and things will be hot so be careful. Most likely from your valve cover.

Hi and thank you for using fixya:
This problem is caused by having a bad head gasket water will leak into your cylinders eventually passing on to the carter where the oil is kept. I suggest you change this as soon as possible as your car can malfunction .
Good luck

You can bypass the core or fix it that's up to you but I would change or remove the thermostat first. If it still overheats then start looking at the water pump and radiator. Hope this helps. Good luck.