by Nat Mann
A common problem in Miatas is that the latch lever can be lowered without first pushing the locking button. New latch assemblies are expensive. Fortunately, the problem is easy to fix with no new parts needed.
This problem is sometimes caused by poor dimensional control when the latches are made. It can also be caused by wear. My left latch was made correctly and had been in use for seven years before it loosened enough to unlatch with a slight pull. My right latch had never engaged properly. In either case a few strokes of a file will give enough engagement to restore firm locking.
#3 Phillips head screwdriver.
Metal cutting file
Small standard screwdriver.
Small Phillips head screwdriver or appropriately sized nail.
First, lower your top and undo three #3 Phillips head screws to remove the latch. If you use a #3 (large) screwdriver the screws should come out easily without marring. Once it has been removed, turn it over. Pry off the E-clip from the lock pivot pin. E-clips love to fly off and seek asylum in the remotest corners of your garage, so use caution while removing. You might want to remove the clip while the entire assembly is inside a large plastic bag.
Once the E-clip is removed and safely stored, the pivot pin is an easy slip fit and can be pushed out. Remove the pin, spring and lock button.
The lock button is the main player here. Let’s take a look at how it works and how to make it work correctly.
On a properly machined latch, the lock and the lever will engage. On a defective latch, the stop surface contacts the stop ledge in the latch housing before there is sufficient engagement to lock properly.
On a worn latch, there may be enough engagement, but there is enough wear in the mechanism to allow the latch to lift too far before it contacts the lock button. Since the lock button engagement surface is eccentric, the engagement point gets higher as it engages further.
Note that the distance from the center to the engagement surface (blue) is about three times as far as the center to stop surface (red). This means that a small change in the stop surface will result in a large change in the amount of rotation of the engagement surface.
If the lock does not engage the latch enough to keep it locked, remove about 1mm –(~1/16 inch) from the surface marked in red.
Here's another view of the lock button:
A) Use a large aggressive file intended for use on metal. A bastard cut mill file will work fine. Your goal is to remove some metal, not just polish it.
B) Be sure to cut both surfaces equally and to keep the file square to the work. Remember that a file only cuts on the forward stroke. Don’t try to cut back and forth. If your file is sharp on the side, put a piece of masking tape on the side to prevent unwanted cutting.
File for a few good stokes, the reassemble the lock and pin without the spring to test. Once there is a solid engagement between the lock and the lever, you’re done.
Place the spring in place with the bent tang in the hole as shown.
Place the lock button in place behind the spring. Rotate it into its normal position; making sure that the stop ledge is between the stop surfaces and the spring.
You can use a small Phillips head screwdriver or a nail to align the pieces. Then remove the screwdriver and replace it with the pin. Snap the e-clip in place and you are done with the repair. Reinstallation is the reverse of removal..
Thanks to forum member Redlugnut for the original idea.
|Back to the Garage||
14 September, 2006