More on that Sticky Hood Latch (Original Post: Dec 20, 2012)

About a month ago, I filed this post about my efforts with my hood latch - its mechanism was stiff and "gritty", and it took a mighty pull to open the hood.  After removing, cleaning and lubricating the two latches, and replacing the Bowden cable between them, I was rewarded with a latch mechanism that was easier and smoother to use, but still required more force that I wanted to open the hood.

So, I recruited my friend John to put some judicious pressure on the hood while I was pulling the release in the car, to see if pushing or pulling on the hood would lessen the force required to release. Turned out that pushing was the right direction, which implied that one of the catches was too tight.

There are two catches on the hood, that go down into the latches.  The stiff spring surrounding the catch is what holds the hood tight after it is shut:

A little more experimentation, pushing slowly and gently on the BMW roundel (hood ornament) yielded the knowledge that the driver's side latch caught significantly earlier than the one on the passenger's side.  If I just pushed until the driver's side caught, then the pull required very modest force to open.  Clearly, the passenger latch was too tight - that is, too short.

This side view might make it a little more clear.  The catch is a post screwed into the receiver that bolts onto the hood.  The spring is captured by the cupped washer, and is free to slide up the latch.  The washer is resting on a shoulder machined onto the post.

The tapered end of the post goes into the latch mechanism, where it is held tight by force from the spring. The latch, shown below, also has a strong spring, and it's the top of that spring that slips past the shoulder on the post, holding it tight.  Pulling the cable retracts the spring in the latch, allowing the hood to release.

So, adjusting it takes two tools: a big flat-blade screwdriver that fits in the slot at the end of the post (visible in the first picture), and a 17mm open end wrench to release the jam nut on the post. You have to force the spring (it is one strong spring) open to the point that you can get the wrench on the nut:

Loosening the post lengthens it, but you don't want to back it all the way out, or that heavy spring will turn it into a projectile!  I loosened it a half-turn at a time, checking the hood operation each time.  It took two full turns to get it to latch simultaneously with the driver's side, at which point the force needed to open the hood was very reasonable.

Two full turns! That's huge! Clearly, this was yet another case of Someone Has Been Here Before.  I suppose it's remotely possible that the jam nut was loose enough to let the post misadust itself through vibration, but it seems more likely that someone was trying to adjust the hood, and went the wrong way.

Yes, I know: if I had done this first, I probably would have been satisfied and never gone to the substantial effort of pulling those latches.  But I'm glad I did - that new cable between the latches is just a bit of security against someday having to open the hood with a can opener...