How to get rid of clunks and rattles, part 2: Going deep

Last week I talked about clunks, thunks, and rattles, the theoretical differences between the three, as well as the process to de-clunk a car. Today we move on to hoods, trunks, and doors, which can be major sources of noise on vintage cars.

I have, at times, become so frustrated with these annoying sounds that I’ve removed the source (a door, for example) and driven without it in order to determine whether or not it is indeed the culprit. Hopefully you won’t reach that point of obsession, and these simple tips will help save your sanity.

Hood

Most cars built since about the mid-1970s have a safety hood-latching mechanism. A spring-loaded latch is located in the nose, in front of the radiator. A metal bar called the striker is mounted on the underside of the hood, typically along with a pop-up spring. When you close the hood, the striker slides into the spring-loaded latch, which closes behind it. Initially it’s latched loosely (the “safety” setting). When the hood is pushed all the way down against the pop-up spring, the striker slides deeper into a groove in the latch, and a second setting on the latch closes on it, holding the hood fully closed. When you yank the hood release lever, it pulls a cable that releases the latch from the deep position to the “safety” position, and the hood, pushed by the pop-up spring, jumps up into that position. You then need to get out, walk around to the nose, move the small lever that releases the latch from the “safety” position, and raise the hood. You know the drill.

In contrast, many vintage cars don’t have a double-latching mechanism or a pop-up spring, and the latch itself may not be spring-loaded. The hood release lever may simply pull a cable that swings a lever into place that holds the hood down.

Whether a car is new or vintage, nearly all cars have some degree of adjustability built into the hood latch. Typically, either the striker or the latch can be adjusted up or down in order to remove play that creeps in through the wear of metal-on-metal (which, as you know from the last installment, is what typically generates a clunk). In the photo below, showing my 1972 BMW 2002tii, you can see the bolts and elongated holes that allow adjustment of the latch.

Another thing to be aware of is the hood standoffs. Most cars have a pair of rubber or plastic standoffs inside the engine compartment that the closed hood rests on. Sometimes, as with my BMW 2002tii, the standoffs are on threaded rods to make them adjustable; it depends on the car. When they are adjustable, the idea is to use them to align the hood with the other body panels, then adjust the latch so it pulls the hood snug against the stand-offs. They’re non-adjustable on other cars, however.

So, now that you know what to look for, go to your car and grab the hood by whichever end it opens from (front or back) and lift. Do this at both corners and in the middle. If the hood doesn’t budge or bang, you don’t need to do anything. If it moves a lot, like an inch or two, it’s possible that only the safety latch is engaging but not the deep latch, in which case you have a serious safety issue that’s much more important than simply quieting down the car.

But if there’s play in the hood, first inspect the striker, latch, and standoffs to make sure they’re not broken and pieces aren’t missing. For example, on a BMW 2002, the hood release cable rotates a lever that in turn pulls against the latch. At the end of the lever is a little plastic donut. With age, the donut cracks and falls off. If it’s missing, the extra play and the metal-on-metal can be a source of banging. In a pinch, people replace the plastic donuts with fuel hose to quiet the thing down.

If no pieces are missing, try adjusting the latch or the standoffs to eliminate the play. If the hood-to-fenders gap looks good, leave the standoffs where they are and adjust the striker or the latch.

Trunk lid

The trunk lid is simpler than the hood. There’s no safety latch, and on a vintage car, there usually aren’t any standoffs. Typically the trunk lid just pulls tight against the weather stripping. Modern cars may have a soft-closing mechanism that uses an actuator to pull the trunk lid closed. If the actuator fails, it can raise quite a racket. But in any case, the method of checking for play is the same as it is on a hood—lift up and push down on the trunk lid above the latch and see if there’s play. The method of adjustment is the same as the hood, but without the standoffs.

Whether the striker, the latch, or both are adjustable depends on the car. On my vintage BMWs, in order to get zero play from the trunk lid, I sometimes need to adjust the striker so tightly against the latch that I have to slam the trunk lid to get it to close. I’ll typically drive it like this, get a feel for the noise envelope, then move the striker a little, making the trunk lid easier to close, and see if there’s any difference.

Doors

The doors can be a rich source of clunks, thunks, and rattles. Doors employ a similar striker-and-latch mechanism as the trunk, except the striker is often a thimble-sized round cylinder. Like the trunk, typically there are no adjustable stand-offs, and the door is typically held against the sealing rubber. And on a vintage car, the rubber is often badly deteriorated, making the door not spring back against it. Welcome to thunk and clunk city.

Test for play by grabbing the door handle and pulling it out, pushing it in, and shoving it up and down. If the handle moves absent of the door, it’s usually trivial to tighten it up, though it may mean removing the door panel. But if the door moves, there’s play that needs to be adjusted out. Whether it’s the striker or the latch that’s adjustable varies car by car. In addition, on some cars, there’s a crucial little nylon bushing (pictured below) that looks somewhat like a corn kernel or someone’s lost front bicuspid. It fits over the end of the latch that goes around the striker, and is often AWOL. Replacing it often allows quiet bliss to descend, at least over that part of that door.

If the doors are tight but there are sounds emanating from their bowels (and there often are), first check the window by grabbing it at the top and gently wiggling it side-to-side. You may see and hear that noise is coming from the window banging against the door where it slides down inside it, due to deteriorated or missing felt. The felt can usually be replaced without disassembling the door.

If the window felt is okay, though, you need to perform exploratory surgery. Remove the door panel to expose the inside of the door (consult a repair manual if necessary) and visually inspect the bottom. Doors have “door brakes” that prevent them from swinging open too far. On certain cars, the door brakes fail, a piece breaks off and is left banging around inside. I’ve also found speakers, wrenches, and big chunks of glass from where the window was previously shattered and replaced. Hey, at least it’s obvious what’s banging.

If you don’t see anything in the bottom of the door, grab the window again, move it side to side, and look and listen. Sometimes the bolts where the window track is affixed to the bottom of the door have simply loosened up, but sometimes the play is from where the part of the window regulator where the window moves on the track, in which case the window regulator may need to be replaced.

If you still can’t find the source of door-centric noise, take a wrench and tighten every bolt you see. Sometimes the attachment point of the window regulator or door lock to the inside of the door is simply loose. Check the door hinges as well, though on a vintage car, usually the problem is getting the hinge bolts off, not them loosening up on their own.

Rattles

Rattles, by their very nature, are harder to find than thunks or clunks. They’re usually caused by small pieces of metal or plastic rubbing against each other, hitting some resonant frequency, and vibrating loudly.

While we’re still in the doors, there’s a pernicious source of rattles that’s easily squashed. Doors typically have a mechanical linkage that connects the inside door handle and the push-down-to-lock button to the interior locking mechanism. Because the linkage pieces need to be able to move, they often have small nylon or rubber grommets at the ends. When these wear out, it can sound like you have several coat hangers rattling around in the doors. If you can’t order the correct grommets, or simply want to quiet the damned thing down immediately, generic rubber grommets often do the trick.

Unfortunately, rattles can come from absolutely anywhere. One thing I like to do is systematically walk around the car and feel every single piece that’s attached to the exterior—every mirror, grille, headlight, taillight, piece of molding, everything—and test it for tightness. If it’s small, I wiggle it. If it’s big, I bang on it gently with my fist. Then I do the same thing inside the engine compartment. If I find something that moves but can’t be tightened, I’ll immobilize it with a piece of foam or a cut-up heater hose. Then I’ll drive the car again. Often it makes no difference (the frustrating “that wasn’t it” syndrome), but you have to go through the process anyway.

Don’t discount the value of looking on user forums. I love my 1999 BMW Z3 M Coupe (a.k.a. “the clown shoe”), but a combination of its very stiff chassis and suspension and certain corners that were apparently cut during manufacturing can make it a surprisingly rattle-y car for something so recent. I traced a motherlode of rattles to the glove box, looked on a forum, learned that “they all do that,” and found a recipe for rebuilding the glovebox to mitigate the problem. Later, I noticed an obnoxious noise, somewhere between a rattle and a clank, coming from the rear of the car. I searched on a forum and learned that, if the handbrake cables aren’t tight enough, the cable housing can rattle inside a clip it passes through. Bingo. I tightened the cables. Instant bliss.

If you are convinced that a rattle is coming from inside the car, sometimes there’s no substitute than having someone else drive while you systematically lay your hands on every square inch of the interior. I even rode in the trunk of my BMW 3.0CSi once while my wife drove me around. It was the only way I could verify whether or not an odd thunking sound was coming from the rear upper shock mounts (it was).

The inability to pinpoint the source of rattles is perplexing to me. It may have something to do with the vague directionality of low-frequency sounds (which is why subwoofers are monophonic). Whatever the reason, I’ve laid my hands all over the interior of cars, only to find that the source of a rattle was directly over my ears—I’d unclipped the sun visor, swung it around to the left to block sun through the door window, then returned it home but failed to snap it back into place.

As I mentioned last week, many of the root causes of the noises in my BMW 3.0CSi stemmed from the fact that the guy who repainted it 30 years ago did a great job shooting it but a terrible job reassembling it. First-layer clunks were caused by loose hood latches, bumpers whose brackets weren’t tightened, and unsecured rear window motors. A particularly vexing noise—one that sounded like the noise made when you take a wooden yardstick, lay part of it on an old wooden school desk, launch the free end so it goes thwang, and pull the other end back—was caused by a long piece of metal trim that was loose. After working on the car for 30 years, it’s finally pretty good.

My advice is this: Don’t obsess over small rattles. Don’t let them ruin your relationship with your baby. There may come a point where you need to let one (or more) go—the rattle, not the car. While loud metal-on-metal clunking indicates that there’s something wrong that should be fixed, a 40- or 50-year-old car is never going to be as quiet as a new car. And that’s part of its appeal, part of its aural landscape.

Rob Siegel has been writing the column The Hack Mechanic™ for BMW CCA Roundel Magazine for 30 years. His new book, Ran When Parked: How I Road-Tripped a Decade-Dead BMW 2002tii a Thousand Miles Back Home, and How You Can, Too, is available here on Amazon. In addition, he is the author of Memoirs of a Hack Mechanic and The Hack Mechanic™ Guide to European Automotive Electrical Systems. Both are available from Bentley Publishers andAmazon. Or you can order personally inscribed copies through Rob’s website:www.robsiegel.com.