April 2008 - Performance Zone
WHY SOME PARTS BREAK
By Performance Specialist Bruce C. Mallinson
I am baffled at the amount of calls I get every day from owner operators complaining about parts breaking on their truck for no reason at all. Why do some parts break? I have said it before, but I’ll say it again – a worn out crankshaft damper. If you have not changed your damper recently, you should consider doing so.
We just installed a Lipe Clutch in an FLD120 Freightliner powered by an N-14 Cummins. The broken Eaton clutch we removed (see photo) only had 120,000 miles on it, and the owner (and operator) said that he only uses the clutch when starting out. The Freightliner had about 1.2 million miles on the odometer and the N-14 engine had been rebuilt about 600,000 miles prior. The engine ran great, but clutches would just not survive behind the stock 500 horsepower engine.
If you look at the picture of the clutch disc, you will notice that the springs are falling out of the center of the disc. I have never seen anything like this in my 43 years of working on engines, and this owner operator is a mechanic-turned-trucker (they are usually pretty gentle on equipment). While talking with the owner, he mentioned to me that the alternator bracket had broken a couple of times, the bell housing bolts would sometimes break, and that the truck did have a slight vibration to it. Now for those of you who have been reading my articles, you know what my next question was: “How many miles are on your crankshaft damper?” His answer was, “I’m not sure – I purchased the truck used and all I know is that the engine was rebuilt 600,000 miles ago.”
The owner of this Freightliner did not know if the crankshaft damper had ever been changed, so we removed it, cut it in half on a band saw and, you guessed it, the floating plate which floats in the silicone was locked up. There is no way of telling if a damper is shot other than if you feel vibrations or simply remove it and cut it in half. They are only good for 500,000 miles, and this is a fine example of the problems that wore out dampers can create.
This frustrated owner operator had already spent over $4,200 in unnecessary repairs because of a worn out damper on the front of his engine. By the way, the cost of the N-14 damper is $630 (it is the largest of all dampers on semi truck engines). A new damper for a Cat is $490, and the one for a Detroit is only $330. When the damper goes bad on a 3406-E Cat it will almost always break the crankshaft, and the average rebuild, with a new crankshaft, is about $25,000.
Why can’t I get you guys to be more aware of your crankshaft damper? How much more proof do you need to believe me when I say that the Teflon bearing on the moving plate inside of the damper, which moves with every injector firing, wears out and contaminates the silicone. And when the silicone hardens, the damper is no longer useful, and damage is being done to your truck. It might not be the crankshaft – it could be the nose of the camshaft, the flywheel bolts, the air compressor, the accessory drive shaft or the input shaft of the transmission. And what about this – I have recently heard about gears in the transmission being completely stripped of all their teeth. That’s right, gears completely stripped, as though they were put in a lathe and machined off. Could it be the damper?
Torsional twisting will always cause metal to break. Something in the engine or driveline will suffer when the plate in the damper is no longer able to move. It is cheap insurance to replace the damper to protect your truck – and your wallet. And you know that these things never break when you are near home, so it will also help to eliminate costly downtime when on the road.
If you want to squeeze the nickel until the buffalo squeals, please don’t do it when it comes time to change the damper on you crankshaft. I can give you several names of owner operators that have been the “victim” of worn out crankshaft dampers. The biggest victim came to our booth in Louisville last year and said he had a 5-EK Cat with 550 horsepower and it cost him 25 grand to have the engine rebuilt and a new crankshaft installed. And when the dealer did the work, they put the old damper back on because some people think that the damper is good forever. Guess what? Just 45,000 miles later, this poor guy’s crankshaft broke again, and another 25 grand was spent. Do you think this owner operator is going to have to work a few more years before he can retire because of the $50,000 he spent in only 45,000 miles of driving?
In 1983 I was a guest of the Cummins Recon Facility in Memphis, TN. After watching some crankshaft dampers being rebuilt, I asked the engineer in charge of the rebuilding department how often the damper should be changed. He said the operations manual calls for replacement every 380,000 miles, however, if he owned a truck, he would change it every 300,000 miles. Remember, this was way back in 1983. Today, dampers are no longer rebuilt, but the price of a new damper has been lowered and the life expectancy has been extended to 500,000 miles. I have worked truck shows and shared booth space with the owner of the company that builds these crankshaft dampers, and he says that at 500,000 miles the damper is worn out. And he should know!
I hate to keep preaching about these things, but if you sat at my desk and talked to 45 owner operators per day, you would be surprised at what you would hear about parts breaking for no apparent reason. The reason, often, is the damper. It might look like a simple part, but it does a lot for your engine, so don’t overlook it. If you have any horsepower-related questions or comments, call me at Pittsburgh Power in Saxonburg, PA at (724) 360-4080 or e-mail me at bruce@pittsburghpower.com.