Failed oil pump pulley...the sad saga of

I posted a few weeks ago about a rattling noise I thought was coming from my supercharger. I have a '05 with a stock blower and motor. 18K miles on odo. The noise would go away after the car warmed up. I thought I was on the trail of a failing bearing in the SC.
About the same time, my oil pressure gauge started reading either 25 psi or zero, but the check gauge light rarely came on. Two years ago the pressure sending unit failed and I had it replaced by the GT Guys in Scottsdale on the way to the LV Rally. At that time we also noted a small oil leak out of the oil pump. I had that replaced at the local Ford dealership under warrantee at the end of 2008. More about that later. I thought I had another bad sending unit and ordered another one.
Anyway, about 10 days ago I filled the car up with the usual 93 and drove about 60 miles running errands. I noticed some valve clatter if I accelerated. I thought I had gotten a bad tank of gas. I went to dinner and parked the car for a couple of hrs. That evening on the way home the engine started clattering like a sewing machine. Didn't miss, no smoke, oil pressure still going up and down on the gauge. Car didn't overheat. I limped on home (12 miles) thinking this is the worst gas I have ever put in a car. I drained the tank and purged the fuel pumps at the connector to the fuel rail. The gas did have some water in it, but not horrible. Put new gas in the car and cranked it up....same horrible clatter...sounded like the timing chain was not tensioned.

Further diagnostics ensued...
1. Pulled the plugs...no metal or residue...they looked normal

2. Checked all 8 pistons with bore scope from above....some mild areas of burned off carbon deposits from the bad gas and water. No holes, normal looking hone markings.

3. I pulled the valve covers...no displaced springs or followers. There was oil present on the cams etc. We did however note that some of the hydraulic lifters were not pumped up with oil. Reaching inside the front engine cover, the R side timing chain was also slack. Hmmm.

4. Put the car on a lift and cursory inspection with the pans off showed no signs of an oil leak. I drained out the engine oil and all 9.5 qts were there. The oil was very black. Let it sit overnight and decanted off the top stuff. There was some non-magnetic "sparklies" in the oil...almost microscopic...probably aluminum. ? if from the chain slapping the timing chain cover. The oil filter had no metal chunks in it.

5. At first I thought the oil pump and oil pump belt looked OK. Surprisingly, the belt was slack but on the pulleys and tensioner. ? had the tensioner failed or loosened.

6. I pulled the cover off the oil pump and the pulley on the pump was spinning freely! A bunch of metal dust fell out. Pictures of the intact pump and the pullley off the pump are below. The splines of the sintered pump pulley are totally gone. We pulled the pump apart and the internals look normal...it rotates freely without binding.

At this point I think my oil pump pulley was failing all along....slowly chewing up the splines. When it finally started freewheeling, the oil pressure dropped and this led to valve and chain clatter as the lifters and chain tensioner are hydraulic. We will pull the rod cap and main bearing cap at the farthest point from the oil pump. I have pulled the oil pan....no metal debis... and the cylinder walls look OK from below also. Nothing looks bad visually. Crank looks OK as best as I can tell. If there is no bearing scoring...maybe I dodged a bullet. The oil took all the heat for sure. A testament to synthetic oils.

Several questions/issues arise...

1. How did the pulley fail? The locking nut was on tight. There are no splines whatsoever inside the pulley. The pump is not fozen up itself or the belt most likely would have failed.

2. Maybe the pulley was installed improperly when my pump was replaced under warrantee. Maybe a broken tooth on the splines. The pulley is usually pulled off and placed on the new pump shaft, as best as I can tell.

3. Is there a better aftermarket pulley out there...billet? The sintered metal splines failed completely...powdered, pulverized.

4. Assuming the bottom end of the motor looks OK, once the new pump/pulley is installed...other diagnostics....check compression, leak down?

5. Anyone else seen a oil pump/pulley fail this way?

6. Doubt bad gas had anything to do with this, just coincidental?

Sorry for the long winded story. Thanks to Rich for his time on the phone trying to figure this out.

Dan you are correct. There are splines on the pump shaft and also inside the pulley. I will take pics of the new pulley, and the pump shaft splines. We took the current pump apart. It was not leaking or bound up, but it was good to do an autopsy on it also (for Frankie's benefit). New parts should be arriving today. Once I check the main and rod bearings, hopefully reassemble the car this weekend and see how things go.

8K miles on this pump....but I suspect (but can't verify) that the failed pulley is the original pulley (18K miles total). The shop manual says to remove and reinstall it as part of the pump replacement protocol.

The rest of the story....

I got all the necessary parts (new pump, belt, pulley, gaskets) overnighted to me. Thanks to Maurice at Duval Ford in FLA. We pulled the oil pan and inspected the two rear rod caps. There was some discoloration from the heat but no metal transfer or galling. The main bearings also looked OK. Put the new pump, pulley and belt on. First thing I noticed is that there is some slop between the pulley splines and the splines of the pump. The pulley is either cast or heat pressed iron. We used red lock-tite and made damn sure the lock nut was fully seated.
I think when my pump was changed under warrantee 2 years ago, the Ford tech didn't seat things. Either rotational slop or the pulley "walking" up and down the pump shaft caused the softer iron pulley to disintegrate. The pump is made by Melling, but the pulley itself is made elsewhere. It can be pulled on and off the pump shaft splines by hand. It does have some screw holes in its spokes that I assume are for a bearing puller.
Once we had things installed, we prelubed the motor by running an air wrench on the pump with the belt off. This pumped up the lifters and timing chain tensioners. Fired up the motor...no clattering or any abnormal noises. Got the car up to temp (its 105 F here) and drove it...70 plus psi at 3000 rpms and 50 at idle.
Things look good and I dodged big problems. #421 must have 9 lives...A dealer tech "shunted" it when it had 380 miles on the odo (http://www.fordgtforum.com/forums/showthread.php?520-A-Comedy-of-Errors&highlight=comedy+of+errors), 3 years later some type of technical glitch and my oil pump eats the pulley, but the motor doesn't seize up. Hell, my house got nailed by lightening 6 wks ago and didn't burn down. I'm either livin' right or the shoe is about to drop. Needless to say...I have no trust in dealership technicians.
I plan on installing a secondary sensor with a warning light to bypass the problematic sending units and gauges. I had a false sense of security that this was not a real low pressure reading. I also plan on pulling the oil pump cover for inspection as part of routine maintainance with oil changes.
Pics posted below.

The two pulleys

The worn pulley on the left must have "tumbled" on the pump shaft generating just enough oil pressure to keep things from seizing. The pulley tensioner didn't loosen up and did its job.

Pump shaft with pulley positioned.

There is motion between the splines. Wonder if this going to be a problem with cars in the long haul. Red locktite got rid of the rotational play.

The pulley on the left is whats left after the splines wore out! The pulley is one piece sintered (heat pressed) or cast iron. When I opened up the cover on the oil pump and belt, a ton of iron dust fell out on me. Looked like rust. The iron reverted back to it's elemental state. It was all over the inside of the crankshaft pulley and inside the crank damper and balancer. Quite a mess to clean up. You would think a more durable metal (billet?) would have been used for such an important engine component (oil pump in a what is essentially a race car).