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1970 Cadillac convertible top up fast idle rattle

Started by Scot Minesinger, May 10, 2012, 11:19:51 PM

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Scot Minesinger

1970 Cadillac DeVille Convertible:

Wondering if anyone else has suffered a rattle coming from trunk/back of top area that is same frequency of engine rpm.  The rattle is not there at all when top is down, so I'm thinking when top is down it presses against lose object that rattles against the metal.  When the car is warmed up with top up the rattle is not there very much except under low speed up hill travel.  The rattle is more noticeable and it is louder during cold start fast idle warm up.  OK, I know the usual places to go, so here is where it is not a source of the problem:

1.  Fuel and brake lines are secured and when they were replaced last summer no change whatsoever.
2.  Seats are not it, remove them put them back no change
3.  Convertible top mechanism is not it, it is very tight, just replaced the bolts, bushings, wave washers and jam nuts on both sides.
4.  Convertible top hydraulic lines are secure.
5.  Wires in trunk and under back seat are secure
6.  The tortion rods that open trunk have the rubber tube at right spot where they intersect.
7.  Top was replaced last fall and no change.
8.  Exhaust is good and tight
9.  Rear suspension bushings have been replaced and there was no change
10.  Rear shocks have been replaced and no change

Any ideas?  I drive mostly with top down, but it would be nice to have that fixed.

Thanks,

Scot
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Scot Minesinger

OK figured it out.  This has happened to other 69 and 70 convertible owners.  There is a plastic "U" shaped tray underneath where the top connects to the metal body that you can see from the trunk.  The trunk hinge edges (pieces of sheet metal) are  about a 1/16" away from the plastic tray.  I installed slit rubber tubing between sheet metal and tray - vibration is gone.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty