hello all, when i open the bonnet of my XK120 it touches the bulkhead. When lifting the bonnet at the front, the hinges at the rear drop the bonnet for a little and then when raising the bonnet open, the rear end touches the bulkhead lightly. The car is at the paintshop and they can’t fix the problem.
Has anyone had this?
Is there a simple fix?
Are the hinges to be replaced?
Any help or experience much appreciated.
BR
Joep
Is the HOOD properly aligned when fully closed? It is level with the cowl with the proper gap? As I recall, the hinges are adjustable up and down at the bulkhead and fore and aft at the hood’s mounting surface.
thnx for your reply: yes it is nicely aligned and with proper gaps. Also tried to adjust hinges and hood on hinges. Unfortunately to no avail.
Probably are the hinges worn out. You should see it by moving the bonnet while watching close.
I once rebuilt these with the use of some old valve guides from my junkbox, but maybe they dont cost much new.
The design of the hinges should allow full adjustment of the bonnet assuming the metal work of the cowl and bonnet are still fairly true to the original shaping.
Do you have the four threaded plates that mount on the inside of the cowl to facilitate the upward/downward adjustment of the hinges? If not, I probably have an extra set of the threaded plates somewhere in my stash of parts.
The strange thing is that the bonnet is really well aligned, nice, even gaps along the whole bonnet. Only when opening, the hinges seem to drop and let the bonnet “fall” too far backwards so that it touches the cowl/bulkhead. Could it be that the hinges are worn out? Unfortunately I can’t check at the moment because the car is at the paintshop…
Yes, even unworn hinges do allow the rear edge of hood to “drop” as it is opened, so that is normal. Once you have access to the car, simply open the hood and see how much play is evident at the hinge pivots by tugging/pulling the hood fore and aft and side to side…any play is a problem. My original hinges still have a nice “tightness” to them. Also, could it be that you are opening the hood too high? Is the prop rod installed, which will tell you how high to go?
Thanks, wasn’t aware that these hinges shouldn’t have any play in them. Next week I will go to the paint shop and check it. (it’s not that I open it too high; it touches just in the first part of opening and then fix it with the prop rod.
Hi all, just to report back on this. Unfortunately it didn’t work out the way I wanted:disappointed_relieved: : new hinges gave same results, no matter what I tried (raise or lower). So have to look for another solution. If anyone has some bright idea, please let me know!
Best regards!
Pictures would help to identify the problem.
Do your hinges look like this?
Yes exactly the same hinges. Do you suggest the are (in)correct?
Car is still at the paintshop, so no pictures for the moment.
Hi all,
Looking at the mechanism of the hinges, I would guess any slippage in the rear pivot arm pivots would result in the rear bonnet edge dropping… This ovaling of the pivot would not be visible. I reckon the cost of new hinges would be more bearable than chipping your new Paint!
With the help of an assistant I observed closely the movement of the back edge of my bonnet as it opens. As the front of the bonnet is lifted a couple of inches - no more - the rear edge does move down very slightly. This is almost imperceptible and we had to do it several times to convince ourselves. Once the bonnet is lifted more than 2" the movement of the rear edge is forward and the whole bonnet then moves forward until it is opened to about 1/4 of its arc.
Then I can feel a change in the hinge pressure. Difficult to describe but similar to what you feel with an over-centre catch. From that point on, the rear edge goes down but it is by then well clear of the scuttle. When on its prop I measured the gap between the rear edge and scuttle to be 3/4" and the edge is 1 1/4" below its starting point.
I have slotted vertical adjustments in the hinges and a fore/aft adjustment in the bonnet. See pics.
It seems to me that if the profile of the rear edge of the bonnet and the scuttle is correct you may have to settle for a bit more clearance so that the rear edge sits a bit further forward.
I’m no good at visualising these complex hinge curves but faced with this problem I think the next thing I would try would be to put shims or packing pieces between the hinges and the scuttle which would move the hinge forward and then move the bonnet back by the same amount. This would shift the axis of the rotation further forward and may give the clearance you need.
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Hi Eric, really helpful this explanation! Never thought of putting packing pieces between the hinges and the scuttle, seems logical now and will try this once the car is back and ready to fit the bonnet.
Many thanks!
and to Jon, tried these new hinges and totally agree that this is worth the money instead of chipping the paint but unfortunately nothing improved with brand new hinges:frowning:
Ok so you have the correct standard hinges. My other thoughts were:
- The alloy cars had a different and poor design.
- Shade tree mechanic hinges from unknown source.
The hinge is what is known in mechanical engineering as a four bar linkage.
Here it is with the bonnet open about a foot.
Link A is the base and doesn’t move.
When the bonnet is closed Link B is rotated a little more to the left.
When you open the bonnet Links B and D rotate to the right, lifting Link C upwards as it moves forward.
Here it is with the front of the bonnet opened 1 foot.
Here it is opened 2 feet, with the tail of the bonnet raised up maybe 1/4 inch.
Here it is opened 4 feet.
You can see the tail of the bonnet actually came down again maybe 1/4 inch, but it is also moved forward maybe 1-1/2 inches.
I didn’t take measurements because it is -10F (-23C) out there.
BTW I did a site search and we have discussed bonnet hinges 188 times on this forum. I even learned that there is a mythical village in Devon between Longbridge and Stonehenge called Bonnethinge.
I would agree with Eric’s idea. I just checked the hinges on my car and the top bolts securing the hinge brackets to the scuttle on both sides have shims. I do not recall fitting these myself so I assume that the body shop did the job following the replacement of the front wings with rust-free west coast examples back in the late seventies.
Chris.
Hi Joep,
Sorry; I somehow missed your earlier post about trying the new hinges, but reading back I now see it. Anyway I hope that the suggested solution with shimming the existing hinges works.
Cheers, Jon.
thanks for your replies guys! Really helpful this forum! The idea of shimming only the upper bolts could be an idea as well. Now first have to get the car back and then I can give it a try
Hi all, report back on how I got along with this.
Car is back (bonnet apart). Made a test formation and experimented with shims. The result: shimming the upper bolts will solve the problem! Now working on everything in the engine bay so the bonnet will be ready to fit in a few weeks:-)
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