The Leak free engine
British cars and motorcycles have always been know to leak oil from their engines, especially the BMC, Jaguar, Triumph etc . . It's a "Tradition" some may say.
There are those who accept the oil stain on the garage floor as "part of the deal" and simply put a tray under the car,.... then there are others who prefer to find solutions. Unfortunately, the solution to this problem is not a simple quick fix, but could be tedious and expensive.
Common causes of a engine oil leak are:
|Inferior or incorrect gaskets fitted, or just poor engine assembly.|
|Worn oil seals, or poorly fitted.||More common causes of persistent oil leak is from worn rings, which allows compression to leak into the crankcase building a positive pressure.||Blocked crankcase vent tube as fitted to earlier small bore motors||Blocked Pressure Control Valve (PCV) fitted to some cars.||Then of course there is the design of the B Series engines. They have no rear main oil seal and rely on a counter rotating oil grove cut into the crank to prevent oil escaping, unfortunately, with today's light oils, this "tolerance"seal just does not work.|
It is my opinion that the main cause of oil leaks on British Leyland engines (assuming the engine was correctly assembled) is caused by the inability to create a negative pressure in the crankcase, like all engines it builds up a positive pressure in the crankcase which is responsible for pushing the oil out the rear main bearing ..over the years BMC tried numerous methods to rectify the situation, including:
|Trying to decrease the crankcase pressure by venting via the inlet manifold, all very good when the throttle is closed at idle, but there is no negative pressure in the inlet manifold when the throttle is opened... when it is needed most.|
|Venting the crankcase pressure to atmosphere via breather pipe fitted to the timing chain cover, or to the cam followers inspection panels. Unfortunately, whilst this will neutralize the pressure it does not create a negative pressure.||And by fitting a PCV to some cars, also ducted via the inlet manifold|
I did a experiment to see what happens when a negative pressure is created in the sump... By fitting the inlet side (suction side) of a 12 volt air pump (the ones used to pump up an inflatable mattress) which was switched on during normal driving.. guess what, it worked perfectly. Unfortunately it is not a practice solution, for obvious reasons. But it proves that by creating a negative pressure in the engine it does solve the problem.
So, how can we practically create negative pressure in the engine?
The problem was addressed by BMC by fitting a vent tube to some models that was directed into the airstream under the car, the end of the tube was cut at a 45 degree angle, which caused a vacuum when driving at speed, but did nothing when there was not much forward motion. .. Problem half solved.
A very effective modification to this solution would be to build a simple Venturi to the end of the breather (remember the Piper aircraft? .. A Venturi was used to drive the air speed indicator and other instruments) .. This system does work, but then again it is only effective at speed.
The answer would be to fit a small 12volt vacuum pump to the end of the vent tube found on the tappet cover. Anyone tried this ?
Many attempts have been made to fit a rear main oil seal (only a split seal can be fitted (Ford have used these) it will certainly solve our problem ... Has anyone had any success with this, and has anyone tried to use or make a leather seal? ... Leather has been use in diff and gearbox seals by Jaguar and others, I have used them successfully.