MG Car Repair: MGA 1600 1960, crank case breather, piston ring

Question
It is leaking oil thru the pipe crank case breather what would that be

Answer
Hi Raul,

Excess oil from a breather pipe can be several things. First check that the oil level is not too high. If that is ok then you need to run a dry and wet compression test. Also, have someone drive the car quickly from a stop while you watch from behind the car to see if there is any puffs of light blue smoke from the tail pipe on a quick start and on a quick shift. Also look at the oil in the crankcase to see that it is not thinned out with gasoline.

If you are not familiar with a "Dry and Wet" compression test, you run a regular compression test on each cylinder (throttle open) and be sure to spine the engine over at least 5 revolutions on each cylinder test. Write down the readings. You should see from 125 PSI to 170 PSI on all four cylinders and there should be very little difference between cylinders.

Next squirt several shots of engine oil (about a table spoon full) into a cylinder and run the compression test again (throttle open). This time the readings will be higher then the standard test but it must not be more then 10% higher. If the "Wet" test is a lot higher, it is an indication of a piston ring problem and if you seen blue smoke from the tail pipe on the acceleration test, that is a conformation of bad rings.

Bad rings causes oil to burn and what is called "Ring Blow By" which causes excess pressure in the crankcase which blows oil out of the breather pipe.

Some of the late MGAs had a breather on the valve cover that routed fumes into the back of the air filter and another breather can on the front lifter cover. Earlier "A"s had just a pipe extending down under the car to let the oil vapors out under the car. It was called a draft tube.

Howard