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opinions on light metallic tapping sound

1K views 8 replies 6 participants last post by  soupnutz 
#1 ·
Have a 98 GT, my last motor was a full Pi swap that started making a light metallic tapping sound. Thought I had a bearing going bad so I did a complete engine swap with a wrecked '07 grand marquis. When the old engine came out I did a full tear down, inspecting in the process to try and figure out what the problem was. I never found anything obvious. The bearings all looked like they had 140K miles but weren't bad. Fast forward to today, the car hasn't ran in two years. I finally get it to the point of running and it's making the exact same light tapping sound. You only hear it at idle, anything over that and the exhaust drowns it out. The only thing that got swapped from the old engine was the alternator, crank pulley, and the oil pan/pick-up tube.

The old engine had clean oil when I pulled it and the new engine still had the oil in it. The oil looked good and when I swapped the oil pan I cleaned it out and there were no metal shavings at all. It does have an exhaust leak I need to fix, but I ran out of daylight and wasn't able to get under it or take a video.

Any ideas on what could cause this? I haven't been able to get underneath it yet, but it sounds like it's coming from the front of the engine.
 
#2 ·
Got my exhaust leak fixed and cranked her up again today for a video. It's coming from the front, drivers side. I probed all over the place with a screwdriver to the ear and couldn't find anything definative. It ran in the driveway for about an hour and I put about 20 miles on it. I think it may have quieted down some afterwards. These videos were taken after I got it running and fixed a miss-fire, but before I drove it around. I can barely hear it outside of the car with the hood down, and I even parked it right next to my truck so it would echo. I don't think it's a bearing or anything, but I can't stand random noises and want to figure out what it is. It does feel like it's down on power, but it also has half a tank of three year old gas with four gallons of fresh ethanol free 91 added with an 87 octane tune. After a few fill-ups with fresh 93, I'll load the 93 tune and see how it runs.

On the bright side, I drove it to the DMV and registered it. Applied for a personalized plate that says
SLOAZ GT. The clerk wasn't sure if it would get approved. We'll see.



 
#3 ·
Sorry, I don't hear any tapping at all. If its not any worse than that I wouldn't worry about it.
 
#6 ·
The closer you got to the PS pump the louder it got. It could be in the timing cover but I think it sound like PS bearings.
 
#7 ·
Thanks for input guys. The PS pump was my first thought also, sounds like it's coming from around there. It didn't do it until I swapped in the last engine, and I put less than 10 miles on that engine before pulling it out.

Good idea about pulling the belt. Can't do it at the moment though. Fuel pump just failed. I suspected it was bad. Was losing power when warmed up and going over half throttle, fuel pressure checked good with no load though. Took it out last night and stress tested it, got it to fail. Now it will crank and idle, but shows 0psi. Any throttle and it dies. Once I get that replaced I'll pull the belt and see if it changes.
 
#9 ·
I haven't done anything else with it. It's diminished somewhat and I don't even notice it unless I'm underneath the car. Whatever it was has worn down I suppose. Maybe next time I'm doing some maintenance on it I'll play around with the belt and see what happens, but for now I'm not worried about it.
 
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