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Adventures with a Trunk Release

 
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Old 08-12-2018, 01:11 PM
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Default Adventures with a Trunk Release

Greetings All,

The electric trunk release function on my '02 had been slowly getting worse. After fixing the problem (new latch/release mechanism), I wanted to share what I found to hopefully save others some grief.

The symptoms: Over the last 2 years or so, the trunk release would occasionally act up. After hitting the button (key fob or dashboard), the trunk didn't always pop open. I'd typically hear the click as the solenoid actuated, but not always. Sometimes the click didn't seem as loud as normal. The behavior was the same with the exterior button on the trunk itself. Usually when the latch misbehaved, all I had to do was just lift up slightly on the trunk lid. I initially thought the trunk seal provided some springiness to help release the latch, and that this seal had become compressed, so I didn't think too much of it. Turns out the seal had nothing to do with it.

In the last few months, the behavior was getting worse. When I did hear the click, it was much softer than before. I often had to use the key to open the trunk, which initially worked fine. After a few weeks of using the key (I don't use the trunk very often, maybe once a week or so), I had to turn the key harder and harder to open the trunk. Clearly something was wrong, and not just on the electrical side. Last weekend I finally had some free time to tackle the problem and was surprised what I found.

I ordered a replacement latch assembly, Jaguar part #XR830399. I found a smoking hot deal for a new one on eBay for only $40, but typically they sell for around $100 - $140. I highly suggest purchasing a new latch and not a used one, as detailed below. As if often the case with a Jaguar of this vintage, the latch had a Ford oval stamped on it, but I didn't see any numbers that might help locate an economical replacement. Please note this part number is only applicable for pre-facelift models. I do not know if the later models are similar:





To remove the latch, remove the plastic trim at the bottom edge of the trunk lid, and peel back the liner. You'll need a T27 Torx bit to remove the plastic trim piece. Once the liner is folded back (I didn't remove it all the way), three bolts secure the latch mechanism to the inside of the trunk lid. Each bolt had a spacer between the latch and the trunk lid, so be careful not to lose them.

The latch assembly has an internal solenoid and two external cables. The longer cable runs up to the external key lock. The shorter cable runs to the glow-in-the dark emergency release handle. In this picture, the key lock cable has been removed to better show the location of the solenoid. Note the white plastic actuator arm at the left, with more details to follow:





To remove the latch mechanism from the trunk lid, I recommend leaving the key cable connected behind the key cylinder. Disconnect the cable from the latch instead, where access is much better. To release the cable housing from the latch, use small needlenose pliers to squeeze the two clips as shown. Once released, the inner cable releases through a slot in the side of the latch's actuator arm.





Here's the problem I found with my old latch. Note how there are three means to operate the plastic actuating arm, one solenoid and two cables. Any one of these inputs will pull the actuating arm to the right, and through some internal monkey motion the actual latch at the bottom is released. When the cables aren't pulled and the solenoid is not energized, the actuating arm is supposed to be spring-loaded to the left as shown here:





After the actuating arm is operated (via cable or solenoid), that same internal monkey motion is supposed to complete a full cycle and reposition the actuating arm to the left, to await the next opening cycle. In this picture, even though the bottom portion of the latch has opened as normal, the actuating arm has not moved back to the starting point:





That was the root cause of the problem. I haven't disassembled the old latch yet, but it is definitely worn. It wasn't a lubrication problem, as all the internal pieces seem to move freely, and a little bit of lube didn't help anyway. I think the problem was the cumulative effect of wear on the individual pieces inside the latch mechanism. The solenoid itself was working fine all the time the latch had been misbehaving. The reason I wasn't always hearing the solenoid click was because the movement of the arm is what makes the noise. When the arm kept sticking to the right, it had no room to travel and thus never made any noise.

With the new latch installed, it works wonderfully. No other adjustments or changes were made. I did notice with the new latch, it makes a distinctive two-part sound when electrically opened, something definitely not there before. The first sound is the heavy click as the solenoid is energized and the actuating arm is pulled in. Remember, the noise you're hearing is the movement of the arm. The trunk pops open and the solenoid is automatically de-energized after about 2 seconds. Once the solenoid relaxes, the actuating arm should spring back to the left. This makes a softer click as it returns to the starting position for the next opening cycle. If your trunk release is acting up, I'd suggest listening for this second, softer click. If you don't hear it, most likely the latch mechanism is worn internally and should be replaced before it fails completely on you.

One last suggestion when working on this latch: From inside the trunk, undo the latch to one of the rear seatbacks. Pull that seatback forward slightly to make sure it's unlocked. That way, if the latch should jam while you're testing it, you can at least crawl in from the front for access.
 

Last edited by kr98664; 08-12-2018 at 02:15 PM.
The following 3 users liked this post by kr98664:
aholbro1 (08-13-2018), JagV8 (08-12-2018), Paul792 (08-14-2018)
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Old 08-21-2018, 10:10 PM
wydopnthrtl's Avatar
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Excellent post Karl! Thanks for the good write up and for using the technical term "monkey motion".
 
 
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