Mustang broken balancer and possible bearing damage.

Question:

1999 Ford Mustang w/ 4.6L engine .. one week ago, outside grooved ring of harmonic balancer came off during rapid acceleration .. drove remaining 8 to 10 minutes home w/ no apparent loss of power in engine or transmission but, up until last minute of drive time, there was terrible noise coming from under the hood – like metal being ground up .. never overheated, no steam coming from under hood .. have not attempted to restart car since driving it home that day .. at the moment, my first concerns are: is it wise to attempt restarting the car to drive it to a shop or have it towed; if car restarts & appears to drive ok would it be wise to continue driving car w/out being checked out by mechanic; likelihood damage was done to engine or transmission; if so, what type of damage likely; would the smartest course of action at this time be to have it towed to shop & have them pull valve covers to see if any rods were ground up & need to be replaced

Answer:

The harmonic balancer pulley drives the water pump as well as your
other accessories for your engine. It also serves an important
purpose of dampening vibrations and preventing bearing wear.
They don’t usually just fly off, so there may have been bearing
problems before this incident, but it’s hard to say. I would suspect
the metallic noise you heard was a bad bearing. (Rod or Main Bearing)
I would not start up your Mustang and drive it to a shop. Towing is recommended.
Here is what could be wrong…

1. Blown head gasket, since the water pump was not being driven when
the belt flew off, it most likely overheated, even if you did not see
steam.

2. Warped cylinder heads (See above). I believe your cylinder heads
are aluminum, and much more prone to warp.

3. Bad rod or main bearing on the crankshaft. The metallic noise and
the fact that your harmonic balancer flew off, points to a real bad
case of vibration coming from a bad bearing. It’s possible the
balancer flying off caused the bearing to fail, but it’s most likely
the other way around… the bad bearing caused the balancer to fly
apart.

I would have the vehicle towed to a shop you trust. A Ford dealer
would not be my first choice, but if you do not have an independent
shop you trust, then they are better than nothing. Have them pull the
oil pan and inspect for a blown bearing. I would also have them do a
compression check and check for signs of a blown head gasket.

If there is a bad bearing, depending on the mileage of the engine, I
would consider a reconditioned or low mileage used engine. If you
take it to a Ford dealer, they will want to sell you a new one, or a
Ford Remanufactured engine… if you are at an independent shop, they
would be more willing to install a lower cost alternative. Also check
out www.GotEngines.com for a quote if it gets to that point. They
have access to quality used engines as well as rebuilt ones.