1998 Mercury Marquis Hammering/Slapping Noise on Cold Start

KJOHN

MEMBER
1998 MERCURY MARQUIS
V8
2WD
AUTOMATIC
130,000 MILES

98 Mercury Grand Marquis 4.6 v8 130,000mi. On a cold start the engine makes a loud hammer/tapping or slapping noise. It is not constant but intermittent. The noise stops when the serpentine is removed. I replaced the idler pulley and the tensioning pulley, and had a good shop check a/c compressor and it is ok. Also the power steering pump and alt. Seems ok. Is it possible that the harmonic pulley could make that kind of noise? What could it be? Also, when the noise happens, I can see that something is locking up as the tensioning pulley arm hunts. Thanks, John

Tuesday, March 30th, 2010 AT 10:39 PM

1 Reply

MERLIN2021

MECHANIC
17,250 POSTS

Most often it's the A/C compressor, not that it's bad, but the bearing in the pulley is. And as it binds, you will get theses symptoms. Common problem at this mileage, did one on my one Town Car. Go to the junkyard and buy a good compressor, or one that has a free spinning pulley. Remove the 5/16th bolt from the clutch, pull it off, remove the snap ring and slide the pulley off, reverse this process on your compressor, no need to open A/C system, or even remove it from the car, Install the snap ring the same way it came off the old one. It's beveled, and it does matter!

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Wednesday, March 31st, 2010 AT 1:05 PM