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Oz34
United Kingdom
2538 Posts |
 Posted - 22/03/2012 : 20:04:03
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There was a thread on this subject a couple of years ago which concluded that the gap between the bottom edge of the bonnet & the valence was about 1cm. I have this at the front end but at the back it's nearer 1.5 however, this is not my problem!
The O/S rear bonnet catch slips out of engagement. The fitting of the catch to the bonnet is clearly fixed with no adjustment. Equally, the loop on the valence is a simple factory produced piece of steel; no adjustment there. If I have excessive clearance as mentioned above, this cannot happen! So, what have I missed?
I'm considering welding a piece into the top of the hole on the loop in order to increase the engagement, but this should not be necessary!
Anyone got any bright ideas. Many thanks in anticipation.
Dave |
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LewPalmer
USA
3243 Posts |
Posted - 22/03/2012 : 22:57:56
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Maybe shim up the rear of the bonnet board by 1/2 cm?
Lew Palmer
Registrar, NAMMMR |
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Robin Macmillan
United Kingdom
415 Posts |
Posted - 22/03/2012 : 23:12:21
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funnily enough I was looking at a PB a day or so ago with the reverse of your problem ... bonnet to near valence ! Anyway for yours
The valence attaches to a small right angle bracket that is attached to the firewall support. Are they set to the correct position. The valence may have been replaced with a thinner section, my one which I believe to be original is about 1" thick but tapered at the front to follow the curve of the chassis to about 1/2". Changing the valence position will be difficult if the front wings (swept) are already fitted as they screw to the valences.
If there is no other solution I would suggest a spacer under the metal plate into which the locking mechanism goes with longer bolts is a better option compared to welding a loop onto the plate
PB 0527 |
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ags
United Kingdom
275 Posts |
Posted - 22/03/2012 : 23:26:07
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Hi Dave,
My simple mind suggested that you check first whether that catch is actually engaging. My (unreliable) memory says that the flat tongue on the hook on the sliding portion of the catches is about 1/2" long, or 1.27 cm in new money, while the movement of the hook is about 1" or 2.5 cm. I would have guessed that both of these should be more than enough to cope with your 0.5 cm discrepancy. (These thoughts were triggered because on my car the front OS catch does need a bit of extra pressure on the outside of the bonnet to get the tip of the tongue properly into position but once there it never comes undone.)
Are the hairpin springs on that catch OK?, because of their over centre action the catch should click into the closed position without the tongue and the hook being engaged. If these springs are broken or missing then there is nothing to hold the latch closed. I have also seen considerable wear on the mating parts of the handle (a comparatively small rectangle) and the slot in the latch piece which might give sufficient lost motion to prevent proper engagement or allow vibration or chassis flex to loosen the catch. If this is the case a little building up using braze or steel Araldite to choice might improve things.
More technical ramblings from
Andrew Smith MMM571
PB Abergavenny |
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Oz34
United Kingdom
2538 Posts |
Posted - 23/03/2012 : 17:13:34
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Many thanks to the three of you. I think I may not have explained myself sufficiently clearly as I think both Lew & Robin have got things the wrong way round. A picture saves......
As you will see Andrew, the springs are fine. The catch is just engaging the striking plate (which I perhaps incorrectly was calling a loop) by about 1mm. If I apply slight inward pressure to the bonnet, the catch pops out. Any raising of the valence would only exacerbate the problem.
The only solutions I can see are to drop the valence, but that will increase the gap to the bonnet or to weld perhaps a 1/4 inch strip into the top of the square hole in the striking plate so the catch has something to bite on. Clearly I don't really want to do that!
Dave |
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Gordon
United Kingdom
692 Posts |
Posted - 23/03/2012 : 17:41:52
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Dave,
Is the rubber seal on the firewall in good condition? If it is too thin it may have some bearing on your problem? Are the side panels of the bonnet original?
Gordon
PB 0331, MG4473
Derby |
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Robin Macmillan
United Kingdom
415 Posts |
Posted - 23/03/2012 : 18:08:54
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Yes I did get it the wrong way around .... comparing mine with yours does not seem to offer a sensible answer. Is the N/S a good fit ? Are the bonnet sides the same size ? Are the bonnet latch positions on the bonnet side the same ? Are the front ones a good fit ? The only real suggestions I can make are
1) bend the tongue up, it does look a little bit less angulated than mine
2) as you suggest, perhaps just wrapping some coat-hanger wire for a trial fix
3) both the above
PB 0527 |
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Oz34
United Kingdom
2538 Posts |
Posted - 23/03/2012 : 18:51:46
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Hello Gordon,
Yes, rubber is brand new; bonnet on the other hand is not original to the car but has been with her for at least 45 years. I didn't notice the problem in a previous incarnation as, when I was driving her in the '60s, the striking plate was not fitted; I relied on the front one only for that side. The other 3 are all working fine.
Robin, I haven't measured latch positions merely assuming (don't ever do it!) that, as you can't shift them they must be right. Perhaps as a start I'll swap the front & rear ones. If then no joy I may look at your idea of bending the tongue slightly.
Thanks again for your interest.
Dave |
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Alan Bertram
United Kingdom
199 Posts |
Posted - 23/03/2012 : 20:58:01
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Hi Dave,
My car had a similar problem with the bonnet catch plates at the scuttle end being a bit too long, a previous owner solved the problem by giving the catch plates a slight Z profile. I had thought of making a couple of short catch plates but found my swept wings in this location pushed the bonnet in before the catch would line up with a shortened catch plate hole. So decided to stick with his fix.
The Z profile is about 80 degrees, which is more acute than it looks in the photograph.
Regards, Alan
PA 0397 |
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Oz34
United Kingdom
2538 Posts |
Posted - 23/03/2012 : 23:17:28
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An interesting solution Alan. I have a nasty feeling this would push my bonnet sides out too far though. I haven't tried the catch swap mentioned above yet, but I'm leaning towards my idea of welding a bit in. I may try & jury rig such an arrangement first.
Nice to know I'm not the only one it's happened to though!
Dave |
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dade
United Kingdom
513 Posts |
Posted - 25/03/2012 : 10:03:43
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Hi Dave
I suggest that you double check that the Bracket is not home made first, it may have been made too long ie sticks up too high.
Judicious bending is also on the cards.
If all the various suggestions do not work, cut through at the angle where the bracket bolts to the bonnet board and take out the appropriate amount and reweld the joint. That would be easier than trying to "letin" a small piece of metal.
Wish you well
Russ |
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Oz34
United Kingdom
2538 Posts |
Posted - 25/03/2012 : 10:35:53
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Thanks Russ,
I'll check on originality but I'm 99% sure they all are; if not I have one spare. Your cut & shut idea certainly sounds a better one though than mine. Thanks for that!
Dave |
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Allan Bentley
United Kingdom
257 Posts |
Posted - 25/03/2012 : 10:40:06
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My P type has the same problem. I welded a small plate in the gap shown in your photo and this has worked well for years. I don't know why it needed this as all the parts are original.
I put it down to the height of the rear bonnet hinge mounting with respect to the chassis frame as this is attached to the bulkhead. I had replaced the lower frame work of the body in the late 60s, and in those days there were no pattern parts so I had to make them myself. I thought at the time the front body mount was at least 1/8th inch too low. The correct thing to do was to shim the front body mounts to lift the tub with respect to the chassis. The rear bonnet hinge socket is then at the correct height wrt the chassis so the catch, latches as designed.
Check the gap between the bonnet sides and the valance if the bonnet is the original and at the correct height the gap should be the same at all 4 corners. Remember also this is just as relevant to the radiator end. Over the years both ends may have dropped certainly the rubber pad under that radiator.
Allan
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Oz34
United Kingdom
2538 Posts |
Posted - 25/03/2012 : 23:50:01
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Thanks Allan,
Unfortunately I'd have to jack the body up 1/2 an inch to get a reasonable engagement; too far I think! Since mentioning the idea of "filling in" part of the hole in the plate, I'm thinking more of cutting & shutting as Russ suggested.
Russ, I've now checked & am sure all 4 + my extra one are original. They're also all the same size. The valences/bonnet boards are the same height above the main body irons so, as the left hand side latches OK the right should......The only other variation I've thought of is the very second hand bonnet that's the property of another car. It could easily be the two side panels are not both from the same car & the latches are at different heights. But that would apply to the front as well, & that's OK. I'll check tomorrow.
Good night,
Dave |
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dade
United Kingdom
513 Posts |
Posted - 27/03/2012 : 08:20:27
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Hi Dave,
From what you have said about the other side being Ok it sounds like holes in your bonnet for the latch are in the wrong place bearing in mind that the bonnet is off of another car.
Check the side panel to see if original holes have been welded up in the past and new ones drilled.
Check one other fact before proceeding, make sure that the bonnet is properly centred at the Bulkhead, even if it is, it may be possible to tweak the bonnet very slightly to achieve a result.
All the suggestions made can be long winded but worth it, to get a good result.
Russ
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Cymber
United Kingdom
966 Posts |
Posted - 27/03/2012 : 22:09:06
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The bonnet board in Alan Bertram's photograph has a notch cut in it to fit around the firewall seal Z sections. The notch weakens the board at this point. My late PA 2032 does not have this notch which suggests that perhaps the notch was done away with and the Z sections shortened. Which is correct for my car?
Maurice Blakey. |
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