You HAVE to let your engine breathe!  Over the years, we have written many articles about the advantages of straight-through quiet-performance mufflers and the fuel mileage gains of ¼ to ½ mpg.  This equates to a savings of about $6,000 per year in diesel fuel.  That is why we design mufflers and promote the Fleet-Air Filters made of several layers of washable foam.  This is a lifetime air filter and will allow the engine to gain another ¼ mpg in fuel savings.  However, there is something else on the engine that needs to breathe, and that is the crankcase, or the oil pan area of the engine.  Blow-by is a by-product of combustion and as the piston is slammed down when the injector fires, the air beneath the piston and some of the combustion that escapes past the piston rings is blow-by, and must escape the crankcase by way of the breather tube. 

Years ago, back in the early 1980s, the breather tube on the older small cam and early big cam Cummins engines would clog from oil deposits and not allow the blow-by to escape the engine.  Being that the blow-by continues, it has to go somewhere.  As the pressure builds up in the engine, it will push the oil down the valve stems and oil consumption will occur, where you can see a bluish smoke coming out of the stacks.  The majority of the blow-by will escape up the turbocharger oil drain line and force the oil out of the seals.  Now when we say seals in a turbo, we think of the type of oil seal on the axles of the truck because that is what we’re all familiar with.  However, because of the tremendous heat inside a bearing housing on a turbocharger, the normal type of oil seal could not live, so the turbo oil seal is actually a small piston ring and exhaust pressure in the turbine side of the turbo (exhaust housing) and the compressed air on the compressor side of the turbo (the aluminum housing) help to keep the oil in the bearing housing.  The oil comes into the bearing housing under pressure and exits the turbo via gravity in a whipped foamy state and must have a drain tube no more than 30 degrees off of vertical and the drain tube has to be about 5 times the volume of the oil feed line.  So, the oil drain tube has a very important function in keeping the oil in the bearing housing and out of the charge air cooler and exhaust pipe.  In order for the turbo oil drain tube to properly perform its function, the breather tube on the engine must be able to breathe.  Now Caterpillar has installed a blow-by canister on the Acert engines due to the fact that a twin-turbo engine develops more crank case pressure, and the canister is supposed to keep the oil found in blow-by from traveling down the tube and landing on the street and accumulating on the undercarriage of your truck.  The Cummins ISX engine has a blow-by filter on the top left side of the engine and there is a one-way valve in the canister filter that could malfunction, creating excess crankcase pressure in the engine, enabling the filter to clog again, creating the excess blow-by pressure in the crankcase and causing the turbo to throw oil into the exhaust pipe or charge air cooler.  Are you getting the picture of how everything must work together on the engine to allow it to function properly?  On August the 10th, Henry Good called me from just south of Scranton, PA, and said he has lost the Turbo.  As it turned out, the hose connecting the charge air pipe to the charge air cooler on the right side of the engine had blown off the cooler.  So, he loosened the clamp and installed the hose and as soon as the turbo developed boost, it blew off again.  Again he re-installed the hose and never made it up the ramp to the interstate.  SO, I had him remove the elbow from the compressor side of the turbo and rev the engine to about 1500 RPM and shine a flashlight across the outlet of the compressor housing and look for oil.  He found oil.   Well, by now it’s 10 PM and I’m ready for bed, so we resumed this problem in the morning.  Now Henry needs another turbo and this is not a stock turbo on the ISX, it is a Holset, just not the original one so we contacted Chuck at CG Customs out of Scranton and he put us in touch with Mike and he went to where Henry was and removed the leaking turbo and installed the new one we shipped to CG Customs.  The next day, Henry Good brings the leaking turbo to our shop and we found nothing wrong with the turbo other than the oil coming out of the compressor housing.   Upon inspection of his W-900L Kenworth, we found nothing wrong.  The air filters were clean.  He wasn’t in a rainstorm:  Wet air filters will cause the turbo to leak oil into the compressor housing as well.  Upon inspection of his crankcase breather, we decided to remove the crankcase breather filter (after more than a half million miles, it was rather dirty).  I must admit that I did not know there was a filter on the breather tube of the ISX (I don’t get to spend as much time in the shop as I would like to, because I have to answer phone questions from owner-operators).  So now every time an ISX comes into our shop with a crankcase ventilation filter, we will be removing it for inspection.  The cost of this filter is $77.51, but this is economical compared to the price of a new turbocharger.  Henry lost three days of downtime and spent about $380.00 in labor to have the charge air cooler removed and cleaned of the oil.  It’s always SO much cheaper to do preventative maintenance as opposed to waiting for the problem to surface.  We now have the ISX crankcase breather filter in stock.

 Written by Bruce C. Mallinson, Pittsburgh Power Inc., 3600 S. Noah Drive Saxonburg, PA 16056.  Email: bruce@pittsburghpower.com. Phone 724-360-4080.