Actually, I don't think they call it an "silent recall", it's something like an "unadvertised extended warranty".
As related in a different thread, my wife's 1996 mustang GT (4.6 liter SOHC V8) started overheating about three blocks from home. There was no traffic so I turned on the heater and drove it the rest of the way home. It was gouting water from somewhere around the alternator. After carefully cooling it off with the hose, I shut it down and started diagnostic procedures.
For awhile I followed a red herring -- an empty threaded hole in the driver's side of the block just behind the alternator. Turns out some blocks had this (depending on where it was manufactured) it doesn't go into the water jacket, and in this model it wasn't used. (Thanks to everyone who helped on this issue.)
Finally I gave up, put everything back together, filled it up with water and started the engine. Since the engine was cold, I was able to put my hand behind the alternator and see where the water was coming from. (Kids, don't try this at home.)
As you probably know, the intake manifold on the 1996 Mustang is plastic. What I didn't know is that part of the cooling system -- a bridge between left and right parts of the block, just behind the alternator -- is also plastic. This part had split along a forward seam.
So, I went to the dealer and talked to the parts guy. He said "you sure you want that? It's expensive". I said other than wrapping the old one in duct tape, I didn't really have any choice. Then he said "You know, the last one I pulled was for a recall repair." Well that's interesting. He loaned me the phone, I called the insurance company to get the VIN number (which I didn't have on me) and then went around the corner to Service.
I asked the service guy what recalls were on this car, and he pulled up two -- a parking brake assembly (common on Mustangs -- our last one had a similar recall) and an.... let's see if I remember the term exactly... "unadvertised extended warranty" on the intake manifold. He asked why, and I said it had split open and was gushing water.
After a long time looking through books and arguing with the other service people, they couldn't find any limit on the warranty (either time or mileage) so he decided to cover it. I had the car towed to the shop and they had it fixed in less than 24 hours. The new part is aluminum.
If your car develops a similar problem, you might check on silent recalls.
Ron
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