I have a cracked oil sump on my renault megane 1999 model.oil is dripping on to exhaust causing it to smoke.how can i fix this myself. i have been told to use steel putty? will this work or is there a better solution.

You need to determine if it is your oil pan, oil sender switch, oil filter, etc. dripping oil onto your exhaust causing the smoke, or if it is coming out of the exhaust itself. If it is dripping onto the exhaust, deal with sealing the affected area. (new oil pan gasket, sender switch, etc.) If coming out of the exhaust, indicated worn piston rings or valve seals.

lost it>?
measure the old one,
but the pitch , you need 1 buck pitch gage, sold in all car stores.
many are 14mm x ?pitch.

had same problem ..use you cars serial vin number and check manufacturing date . as that is where the problem lies...1 month can mean a totally different part required.

Is it over heating? If there is oil in with the coolent, It could be a cracked head gasket on the engine, Or evan a crack internally in the engine block,

You likely have worn valve guides

This being a diesel, lack of compression is your worst enemy. These symptoms sound like a blown head gasket. Check your coolant for signs of oil, and check your oil for signs of coolant. (oil will be milky looking) Also indicative of a head gasket problem is an oil or coolant leak from the engine as well. If you see no evidence of the above, have a compression test done, and it should show up.

Symptom: White smoke or water vapor from the exhaust. You notice white smoke coming from the exhaust when you start your car. If it is cold out, this may be normal. If the smoke does not disappear after the car is warmed, you have a problem. Possible causes:

1. Transmission fluid may be entering the intake manifold through vacuum modulator.
   The Fix: Replace vacuum modulator
2. Cylinder head gasket(s) may be bad.
   The Fix: Replace cylinder head gasket(s).
3. Cylinder head(s) may be warped or cracked.
   The Fix: Resurface or replace cylinder heads. (Resurfacing is not a DIY job)
4. The engine block may be cracked.
   The Fix: Replace engine block.

Black smoke usually means a rich mixture. For some reason the car is getting too much fuel. If the check engine light is on then take it to a shop with a code reader. They can tell you what sensor needs replacing. These newer cars are usually totally computer controled so if a sensor goes bad they will adjust the mixture incorrectly.

It is very possible that there is still unburnt oil on/ in your exauhst and that could cause your blue smoke. Check your dipstick for signs of water or murkiness to make sure that there is nothing else wrong and be sure also to check under your car for any other possible leaks. after parking it overnight, you should be able to see if there is anything leaking a substantial enough amount to cause the burn off you are talking about.