Let It Breathe

You have to let your engine breathe! Over the years, I have written many articles about the advantages of straight-through mufflers and the fuel mileage gains of 1/4 to 1/2 mpg (this equates to a savings of about $6,000 per year in diesel fuel). That is why we design mufflers and also promote the Fleet-Air filters, which are made of several layers of washable foam. This is a lifetime air filter that will allow your engine to breathe and to gain another 1/4 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. 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 called blow-by. This blow-by must escape the crankcase by way of a 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 pressure builds in the engine, it pushes the oil down the valve stems and oil consumption will occur, creating a bluish smoke to come out of the stacks. The rest of the blow-by (the majority of it, actually) will escape up the turbo oil drain line and force the oil out of the seals.

Now, when I say “seals” in a turbocharger, we think of the type of oil seals on the axles of the truck, because that is what we’re all familiar with. However, because of the tremendous amount of heat inside a bearing housing on a turbocharger, the normal type of oil seal could not survive, so the turbo oil seal is actually a small piston ring. 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. The bearing housing must have a drain tube no more than 30 degrees off of vertical, and the drain tube has to be about five 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 turbocharger oil drain tube to properly perform its function, the breather tube on the engine must be able to breathe. Caterpillar has installed a blow-by canister on their Acert engines due to the fact that a twin-turbo engine develops more crankcase 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/or 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 now beginning to see the big picture of how everything must work together on the engine to allow it to function properly?

Back on August 10th, Henry Good called me from just south of Scranton, PA, and said that he had lost his 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, but he never made it up the ramp to the interstate. So, the next thing I had him do was to remove the elbow from the compressor side of the turbo, rev the engine to about 1,500 RPM, shine a flashlight across the outlet of the compressor housing, and then look for oil. He found oil.

Needing a new turbo, we contacted Chuck at CG Customs in Scranton, and he put us in touch with Mike, who went to where Henry was and removed the leaking turbo and installed the new one we shipped to CG Customs. The next day, Henry brought the leaking turbo to our shop but we found nothing wrong with it other than the oil coming out of the compressor housing. Upon inspection of his W-900L Kenworth, we found nothing wrong. After determining that the air filters were clean and dry (wet air filters can cause the turbo to leak oil into the compressor housing), we were a bit stumped!

Then, upon inspection of his crankcase breather, we decided to remove the crankcase breather filter, and after more than a half million miles, it was dirty. So, now, every time an ISX comes into our shop with a crankcase ventilation filter (see photo), we will be removing it for inspection (the photo shows what a dirty filter looks like compared to a new one). 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 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 filters in stock.

Like I said before, everything must work together on your engine to allow it to work properly. If your engine can’t breathe, it won’t work right, so make sure that your crankcase ventilation filter is clean and doing its job. If you have any comments or questions, I can be reached at Pittsburgh Power in Saxonburg, PA by calling (724) 360-4080 or via e-mail at bruce@pittsburghpower.com.