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Last Update: 10/07/2006 (originally published spring 2002) My car only had 16,000 miles on it when I got it, and it was really tight. I was surprised because I had always heard about C4 rattles and squeaks.
One thing is obvious. The clamshell hood, a dramatic styling element, is responsible for much of the C4's perceived looseness. And, it turns out, much of it's interior noise, including rattles, squeaks, and groans. These are noises you would think to be related to the dash area.
My car, once I got used to it, had several sharp-sounding rattles, especially in the right dash area. Also squeaks and other rubbing noises.
I noticed that if I lubricated the hood hold-down pins and their sockets, a lot of the rubbing and squeaking noises went away. For a while at least; they would come back, sometimes in one day.
But the real point was I would have sworn that those noises were in the dash structure. They were not. They were actually being transmitted through the firewall. And that was the discovery.
Three objectives:
1. Eliminate the rubbing squeaks and groans permanently. 2. Eliminate, if possible, the "jiggling" of the hood as the car goes down the road. 3. And last, but not least, look for any other noises that were related to the hood.
Lock-Down Pin modifications.
First I got some 3/16 inch thick neoprene rubber (already had it from a boat project). I fashioned a "donut" like piece to go over the pin. It's job is to
1) hold lubricant for an extended time,
2) regardless of lubricant, act as an isolator between the pin pad, and the lock down pad, and
3) because it is compressible (different from the spring), it allows me to really snub down the lock pin.
See the picture:
Once the piece is lubricated with grease, fit it onto the pin. Then loosen the locking nut at the base of the pin, and adjust the pin to be as tight as possible, and still be able to close the hood without having to slam it so hard it is damaged.
Don't worry. This adjustment is only about how tight the pin holds the hood.
The alignment of the hood to the panel is done with the separate adjustment pads. You may check this first.
NOTE: Be sure to close the doors before doing any of this. The hood has been known to hit the door if the door is open. Doesn't happen usually, but only once can ruin your day!
Once you are sure about the positioning, go over the pin again, and make sure it is a tight as you can stand it. It is important for the hood to be held very tightly by the pin, as that is what stops it from jiggling when it is driven.
You may have to experiment with how tight is tight, as no two cars are alike, but you will immediately notice how much tighter the hood looks when you drive, and how much quieter it is.
It is incredible how much generic "noise" comes from the pin socket, and the moving hood.
So that's objectives 1 and 2.
Now we are going after the alignment pins.
Once you are comfortable with the hood adjustments, here is another problem that creates an incredible amount of noise... in this case, a rattling type of noise, out by the ends of the dash, near the doors.
Look back at the hood, near the lock pin. You will see, lower down, a sharp pin about the size of a pencil.
Follow it down, and you will see that when the hood closes, it fits into a square, plastic lined, hole in a bracket located near the door hinge area.
If the plastic liner is still there, it is probably loose. More than likely, it is gone. One of mine was gone. When the pin is in the hole, plastic or not, it rattles sharply when the hood moves as the car is driven.
Even with the improvements we just made on the lock down pin, the rattle will come back.
So I made a piece of rubber and fit it into the square hole in such a way that the pin slides into it, and it is prevented from rattling.
It is held tightly, but more important, it cannot touch the bracket.
See the picture:
This rubber piece has to be positioned carefully, and lubricated with grease, so the pin will go in. I cut the rubber piece like the drawing, and as you can see in the photo, the notches hold the front up, which holds the piece in the right position.
So that's it.
A quick mod, and an essentially free mod, and as big an improvement as you can imagine.
Objectives 1, 2, and 3.
Unless, that is, you have the world's only Corvette with a quiet clamshell hood. By the way, you might be surprised as I was by how many noises go away that you would not have associated with the hood.
Summer 2004 update: The original article was published in the spring of 2002, right after I did these mods. In the summer of 2004, I have just replaced all of the rubber parts. The were still in place, and working (better than the original plastic), but they were showing signs of wear and age. So you can count on about two years or so, with occasional re-lubrication. |
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