Logo

Yoda · #**8291** 03-17-2017, 11:37 PM

Leaving the neighborhood (in a heavy rain, of course) on Tuesday in my F150 taking my youngest to school, I suddenly lost power steering and got an alternator light. Felt exactly like the engine had died, but still had RPMs on the tach. I figured I'd broken a belt, but when I popped the hood, the belt was still intact. Muscled the truck back home and made some alternate arrangements for the kid, then went and took a hard look under the hood. I could see that the outer rim of the harmonic balancer was a full belt's width forward of all the other pulleys, which caused the belt to jump off behind it. Was going on travel so didn't get a chance to work on it til today. Turns out the outer piece had separated from the center and worked its way almost completely off. When I took it apart the outer piece came off very easily in my hands. I'm pretty lucky that it didn't come completely apart while the engine was running. That outer rim weighs a couple of pounds, and there isn't an easy path out of the engine bay because there is a crossmember right under it with a metal shield running up to the base of the radiator. That piece spinning at 1000 or more RPM would have bounced around in there for a while and destroyed the fan and radiator, and probably some bodywork and the alternator too. I've never seen a failure like this before.

Nerfbar · #**8292** 03-18-2017, 08:56 AM

What year and how many miles please?

Yoda · #**8293** 03-18-2017, 03:52 PM

Quote:

Originally Posted by Nerfbar

What year and how many miles please?

It's a 1999 F150 4x4 with a 5.4. 196,000 miles.

Vicegrip · #**8294** 03-18-2017, 07:34 PM

At 196K it owes you nothing.

Harmonic failures are not uncommon. Most times it is noticed and fixed at the real bad vibration point rather than the disconnection point.

Yoda · #**8295** 03-19-2017, 12:57 AM

Quote:

Originally Posted by Vicegrip

At 196K it owes you nothing.

Harmonic failures are not uncommon. Most times it is noticed and fixed at the real bad vibration point rather than the disconnection point.

Concur. I've gotten a lot of good work out of this truck!

Didn't get any vibrations or other warning signs at all. Worked great right up until it didn't. Making the outer ring the driver for the serpentine belt allows for fewer parts than the early V8 engine designs where the pulleys were bolted to the inner section but also puts a lot more stress on the metal to rubber bonding, and has much more interesting failure modes.