Yesterday on the way back from a job our company dump truck started smoking, missing and lost power. It was taken to the shop and the mechanic said the aluminum pistons melted iside the steel block and the engine was toast. He said the cause was driving the truck at excessive speeds. It was later found out that the driver was driving at 80 mph. The truck is a 99 Ford F550 Super Duty Dump Truck with only 73,000 miles. Can this indeed be the cause of the fried engine? P.S. I had to answer F450 to the model, because F550 was not listed as a choice.
I would strongly suspect that the engine was overheating. Possibly speed was a factor. But if the temperature gauge was operating I feel sure it was indicating an extreme overheating condition when hot enough to soften aluminum. I have seen that happen once on a gasoline engine operated with a burst radiator hose and driven until it seized.
The speed of the truck is not important. How fast was the engine turning? How much oil was in the engine? How much coolant? Did it overheat?
Does the engine have a rev limiter?
I get passed by lots of trucks going 80, and they don’t all have melted pistons an hour later.
Thanks for your reply. I too have been passed by many trucks when I am driving at 70 mph. I will gather the information for your questions and get back.
80MPH is really fast for a dump truck but likely not the engine.
Is it possible the driver left it in a lower gear and overheated it or stressed it out while going 80MPH.
I don’t suppose the truck had a way to monitor the exhaust gas temperatures? If it had, the driver should have noticed the temperatures getting to the extreme, and if they had any sense would have backed off on the speed.
Tester
I’m not familiar with this type of truck but I doubt that speed has anything to do with it.
It’s more than likely related to overheating or possibly a problem with the fuel management? Maybe the latter could have acted up and which then led to a lean condition and which then fried the pistons out of it. Just wild guess theorizing on my part.
No matter the cause, maybe the driver should be reamed a bit for doing 80 MPH in a dump truck.
Who drives 80 mph in a dump truck, and then confesses? I go with a lean condition that exhaust gas temp. monitors would have alerted you too, but the simple act of drixing 80 mph (engine speed taken into consideration) should be OK.
Reminds me of the story of when Coleman Hawkins (the first great jazz tenor saxophonist) burned out the motor of his Cadillac racing to catch up with the band he was in (Fletcher Henderson’s) after an all night jam session.
This was in the late '20s.
He drove as aggressively as he played and later that cost him his license.
Um…diesels always run lean.
Thanks, I was trying to figure that one out too.
So lean as they burn pistons? I was seconding OK4450’s comment on a fuel management problem. Took a look at some technical data and nothing is mentioned about a characteristic “run lean” design (not saying it is not true) but something did catch my eye, exhaust gas temp is half of what a gas engine is.There is a pre-chamber, chamber set-up on some examples, i wonder if this relationship got disturbed?
I was thinking more of a injector with a poor or minimal spray pattern that sent egt’s up
My limited understanding of diesels is that there is no control/restriction of the intake air. The engine output power is controlled by adjusting that amount of fuel that goes in. If so, the only way to enrich the mixture would be to step on the gas and travel even faster.
I don’t work on many diesels but enough pass through that I am aware of pre-combustion designs that were prone to burning pistons and understand that none of the current generation of domestic diesels use that design. But a quick glimpse into a couple of industry complaint boards indicates that the “hot chips” that increase diesel power by increasing the fuel charge and advancing the timing are causing pistons to crack and melt in severe duty. Sooooooo, was the engine ‘chipped?’
I suppose if he drove with the engine redlined the whole time, this could happen.
Any engine that can’t handle being operated all day at less than redline as long as it has good oil and a normally functioning cooling system would be a pretty poor design, especially for a heavy-duty truck. This is how engines are tested for days on end during development. So possibly the cooling system or oiling system was out of whack.
What, next you’ll be reminiscing about how you designed circuits with vacuum tubes and “condensors”? :>)
Virtually all diesel vehicle engines have some sort of RPM limiter or governor to protect the engine…
Was the engine disassembled to determine that the pistons had “melted”??? Or was that just the mechanics explanation as to why the engine had failed…
I have heard that sustained high speed driving with a diesel engine can increase exhaust gas temperatures and damage the engine. I don’t know about melting the pistons, though, but I suppose that could happen. I have also heard this is usually more of a problem with diesel engines with performance chips or programmers, so if the truck has been chipped, lack of monitoring EGT’s could have caused this. Otherwise, a fuel system problem is a strong suspect.
Diesel engines are designed to run at maximum RPM without skipping a beat. Redline is an arbitrary marking on the tachomemter. Usually the electronics in modern diesels keep this at bay.
Hey, I’ve got a 3000VDC supply out of an old electron microscope sitting beside my desk right now that has a tube (8068 industrial beam power pentode) in it, waiting for a unique and outrageously overpriced little replacement transformer.