Jag-Lovers XJ6 Hood Release Solutions

Also available at http://www.jag-lovers.org/technical.html

A. Overview:

A common problem with series I-III XJ6's is that, with age, the bonnets pop open unexpectedly. Since XJ6 bonnets hinge from the front and also have a strong backup catch, this isn't the disastrous occurrence that it can be with rear-hinged bonnets. But it is bothersome and, if left untreated, can result in futher damage and expense from the loose bonnet bouncing around (i.e. the welds in the picture below fail and your little problem turns into a big problem).

Here's what the intake-side bonnet pin looks like from the rear:

1. The assembled product:    2. The individual parts:                         
                                                                   
    bonnet top                     bonnet top                               
___________________          _____________________                      
  \     .-.     /  \             \             /  \                     
   \  #######  /                  \  #######  / <- Sheetmetal U            
    \*#######*/                    \*#######*/       channel                
       =====                        ^   ^   ^                                
       =====                     weld  Nut weld                         
       /---\                                                               
        ///                            .-.  <-top of bonnet pin                           
        ///                            |~|  <-bonnet pin (threaded)              
        ///                            |~|                              
       \---/                          ===== <-- pinch nut                 
         V                            =====                             
                                      /---\ <-washer                    
                                       ///                               
                                       ///  <-spring over the pin       
                                       ///                                
                                      \---/ <-washer                    
                                        V   <-end of pin which engages  
                                                the striker plate       

Below is a collection of articles from Jag-lovers on the subject:

Dave Wood, wrote about the rhs of the bonnet occasionally popping open. I too have had this problem especially when I first got my XJ6. My friendly Jaguar speciallist helped me out by showing me the recognised method of closing the bonnet. You stand to the front centre of the open bonnet and place the hand on finger tips centrally on the bonnet, then push firmly so that the bonnet shuts with a "clunk". This ensures sufficient force within the flexing bonnet to snap shut in the locks. If the bonnet pops up on one side NEVER push that side back down as the bonnet can bend, always open and start closure afresh.

Try it out, I've had no trouble since adopting this technique.

Cosmo pleads...

The bonnet on my XJ6 SIII as started to open when on the move. This is a tad annoying and has now become serious as both sides now do it occasionaly. The Fine Manual only mentions adjusting the release cable and I can't see any adjustment in the catch mechanism. Is there any trick to this?

This was happening on the Daimler for a long time before I got around to fixing it.

I loosened the pinch nut on the bonnet pin and turned the bonnet pin a few turns to make it longer, then retightened the pinch nut. It was really very simple. I did this to both sides of the bonnet and now it's stopped popping up. Previously, I had increased the spring tension on the catch mechanism and it didn't help at all.

If somehow you mess up and can't get the bonnet released (say the bonnet release cable breaks), there are little access holes in each wheel well thru which you can insert a slim screwdriver and manually release each bonnet catch. Just to be on the safe side, I practiced opening the bonnet this way a few times before I started messing around with the catch mechanism.

Lawrence Buja wrote: I loosened the pinch nut on the bonnet pin and turned the bonnet pin a few turns to make it longer, then retightened the pinch nut.

That's indeed the method. I just thought I'd insert a small note of caution here, based on my own experience with two elderly XJs. You need to keep the adjustment to a minimum; when you push down on the closed bonnet where the latches are, you should not be able to push it down noticeably. The reason is that if the bonnet doesn't sit down tightly on its guide blocks, it can wobble slightly sideways and the pins (or rather, the bonnet rib their mounting nuts are welded to) fall prey to fatigue fracture. This may not be a concern on smooth city streets, but out here in the sticks it sure is.

If anyone has fractures around those nuts, I can give you details of a repair/reinforcement I did that seems highly successful.

myself worked on it with no solution: ... MY HOOD WILL POP OUT UNEXPECTEDLY.... This will happen usually if I hit a slight bump on the road. First one side will come loose, then about 5-10 minutes of driving

Boy what a familiar problem. I went through exactly what you went through here in Sydney. I took the car to Gary Walker Jaguar...

[ed: several lines of libelous slander deleted]

Anyway, basically he had the car 3 times, and each time he said he had it fixed, and lo and behold, you couldn't drive 2 blocks without it popping again. All the parts had been replaced, so what the hell was going on !!!

I was so angry I could have killed these guys.....anyway, I calmed down, got the car home and had a good look at the latch. What I noticed, was that the bolt sticking down from the bonnet on the problem side, was not sticking out at the same angle as the bolt on the other side. Even though both sides slid into the hole easily, it was just a fraction of an inch out.

All I did was tap it a few times with a rubber mallet, to get it parallel to the other pin. It closes just as easily now, but has not popped in the 2 years since. Also, no damage to the pin or bonnet. I had to tap it towards the back of the car. The more it was tilted towards the front, the more the bonnet(hood) would pop.

Sure this may not be the problem with yours, but it sure was with mine.....amazing what a couple eighth's of an inch can do in a jag....

Aygen E. Dogar wrote:

Now my problem and it's been a frustrating one as several people including myself worked on it with no solution: ... MY HOOD WILL POP OUT UNEXPECTEDLY...

Aygen,

Believe it or not, our car had the same problem. Boy, we messed with adjustment, hood pin springs (even removing them at one point), cable adjustment. etc.. It would sure strike fear into occupants' heads when the hood jumps up 2 inches at 70 mph! On one trip of several hundred miles duration, I got out and adjusted the inner headlights to compensate for the always-up hood, so that we could see the road adequately.

Ok I'll quit with the stories and tell you what we did which stopped the problem. I removed the striker plate assemblies and replaced the plate retraction springs with ones of higher stiffness. I noted that the coils of the old springs had begun to separate, indicating that the original preload wound into the spring had been lost. All tension springs have a wound-in preload during cold-forming which gives the spring a non-zero initial takeup force.

There is another thing to check when an XJ's bonnet won't stay closed. Be sure that the screws--particularly the Phillips head ones--holding the latch mechanisms to the body are TIGHT. They have a tendency to work loose, and an early symptom is for the bonnet to pop open. If they get real loose, however, you will have trouble getting the bonnet to open at all. For some reason--at least on my 1979 SII--Jaguar did not use lock washers on these screws, even though there seem to be lock washers on just about everything else! Needless to say, mine now have lock washers, and they haven't worked loose in a while.

Loose diagonal struts (from the firewall center to the fenders) can also cause bonnet problems, but you should probably hear some "clunks" over bumps or in turns.

One more thing. PLEASE don't push one corner of your bonnet down to secure it. That's a real good way to warp it. Re-open it fully and then close it from the front center (top of the grill) like Sir William intended.

Cosmo wrote:

The bonnet on my XJ6 SIII has started to open when on the move. (Snip)

I have noted various solutions posted but nobody seems to have mentioned moving the spring loaded striker plate forward (towards the radiator) so that the latch more aggressively engages the bonnet pin recess. Observe each striker plate and, if this is the problem, the one popping open will be obscuring less of the aperture. On my car (1985 XJ6 Series III) the striker plate, when properly adjusted, forms a half moon crescent which obscures about fifty percent of the hole. Adjust by loosening the two bolts which hold the mechanism (one on either side of the aperture through which the bonnet pin travels). If there is no forward adjustment possible, remover the bolts and elongate the slotted holes using a round file. Should the bonnet pin be striking the aperture, and the pin is not bent, loosen the three bolts that hold the bracket and reposition the entire assembly. Again this may involve elongating the bolt holes in the bracket. If this doesn't work, the try the rubber mallet suggested in the earlier post - perhaps by leaning out of the window and hitting it every time it pops up.

Thanx for all the suggestions for the bonnet closure problem. After a few days of playing with them the final solution was the rubber mallet. A few taps to knock the bottom of the pin further towards the rear of the car and presto! All other attempts to close the bonnet corectly, adjust the spring, adjust the cable, clean the mechanism didn't work.

Thanx again,

My SIII bonnet hinges were going rusty, such that it was becoming difficult to open the bonnet without a lot of heaving on the structure - a common failing apparently, but never mentioned in ANY of the reports I have seen on an XJ6 (why? Do all the hacks just rehash each other's work? I digress.)

After a local garage had fixed the hinges, the bonnet shut and opened with no trouble, but occassionally the rhs would pop open out of its catch. Rather than taking it back, I noticed that the bonnet was not catching properly when it was should, although it appeared to do so. A final press in the offending area made sure the bonnet catched, and stayed shut.

Cheers,

Hi all,

I think (read "hope") I've finally solved the popping hood/bonnet problem on my '87 SIII. After trying shortening the spring, filling flat the ledges on the pin, the rubber mallet, etc., etc., it was getting to the point that every time I used the car it would pop on the right side. Sometimes I couldn't get to the end of my driveway without it popping loose.

Anyway, here's what I did. I had tried the rubber mallet solution before but I was never sure which way to bend the pin. So, I put a piece of paper towel over the latching part and gently closed the hood/bonnet until the pin made a slight indentation on the paper towel. The couple dirty circles on the paper showed that the pin was off center. A couple of whacks with the mallet in the proper direction (back and in toward the center on mine) and it hasn't popped in days.

Tom (fingers crossed that this really worked and I'm not dreaming)