MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - safety catch captive nuts

does anyone know where i can find the captive nuts and screws for my 73b hoodsafety catch thanks les
l.f. frank

les. I need more information to answer your question. The cross-point screws should be a standard size and available at any good hardware store. The one I measured, from my 68BGT, was either a 10-32 pan head machine screw or a 2BA pan head machine screw (effectively, they interchange and either size screw will fit into either size nut) with a .485" threaded shaft. This would be a nominal 10-32 x 1/2" machine bolt.

I am not sure about how the captive nuts are secured (which is what makes them a captive nut). On my 68, with the aluminum hood/bonnet, it looks the captive nuts were installed before the hood was fully assembled and that replacement would require cutting into the assembly and then welding in a patch. Perhaps someone with experience in this area will be able to answer that portion of your question.

Les
Les Bengtson

Hi Les

I had this issue a little while ago and used plastic inserts that have a square split part that pushes into the hole and when the screw is driven in the split part expands to lock them in place, from the local speed shop. I had to file the holes in the hood square so that these inserts would not turn when driving the screw in. I used 12 Gauge self tappers as the screws. Works a treat.

Herb
Herb Adler

I tried to get some recently but they were not available. Herb has the right idea. That's what I've done and it works well.
Richard Coombs

Are plastic inserts strong enough for the safety catch, when the bonnet springs open at speed?
Paul Hunt 2010

My bonnet springs open at low speed now on smooth roads, so I have made doubley sure my safety catch is secure. For the life of me I can't find anything wrong with the hood latch system, but am about to simply replace it all but the safety catch screws are rounded so they may be drilled out soon. I'm ready to bolt my hood down. Very nerve racking.
R.W Anderson

The bonnet can spring open if the pin is screwed too far into its bolt, if the cable is preventing the latch from springing all the way back, or if the head of the pin has worn on the side that engages with the latch. This last can be worked around by turning the pin a quarter turn or so, which should barely affect bonnet shut alignment.
Paul Hunt 2010

The cable has play in it, allowing for full release of latch on car. Latch is covering about half the open hole where pin comes down. I've turned the pin up and down into nut in bonnet, with no affect. It acts like someone just pulled the handle under the dash. Spring around pin has good resistence. With hood closed, it lines up properly with fender. Pushing down on closed hood shows about 1/2" downward movement. All the pushing, pulling, bouncing while car is parked cannot get bonnet to release. Drive down the road and within 10-15 minutes it will simply release and luckily catch on safety latch.

I did figure out that there is no locking nut on the pin where it threads into the fixed nut on the bonnet. But the pin doesn't move. Oh, and trying to twist the pin & spring show them as being very sound, so it isn't that the pin is slowly threading loose while driving.
R.W Anderson

RW. A half inch of movement, with the hood closed, is far too much. You need to take it down to where you can just feel a very slight movement of the hood, when latched.

Les
Les Bengtson

My inserts aren't the same as Herb's. They have an expanding rubber section and appear pretty strong, certainly better than plastic. They were supplied when I ordered BHA4338. My original problem was the holes for the captive nuts had been badly distorted when, presumably, the bonnet opened at speed. Certainly the sprung sections of the captive nuts could no longer reliably hold the safety catch. In the end I had a piece of 2mm alu welded over the old section and had it drilled to take the new parts.
Richard Coombs

They may be metric but would "nut-serts" work?(put in like a rivet but with a threaded lower part to accept the bolt/screw)
Michael Beswick

"A half inch of movement, with the hood closed, is far too much"

It depends, if the bonnet lines up with the wings then it could be correct. Having said that 1/2" of movement if it *does* line up, is a lot, it's basically the depth of the flange on the sides of the bonnet. Mine barely moves down at all and only has about 1/8" to 3/16" to the chrome grill surround, and is resting both on the buffers on top of the grill and those in the wing channels. If you don't have those buffers and there is more clearance to the grill then it is probably the bonnet bouncing down on its own and coming back up to hit the latch that is springing it open. So if your bonnet sides line up with the wings you need something i.e. buffers underneath it to stop it going down so far, rather than adjusting the pin so it pulls the bonnet down, especially if that leaves the bonnet lower than the wings. However if the sides stay where they are when the middle is pressed down, then that extra tension may well be enough to stop the bonnet bouncing down from the latch and hence stop it bouncing back up again to shock the latch open.

My latch covers slightly less than half the hole, as shown, unless you mean the top and bottom edges of the latch ignoring the curve between them, which probably is about half-way.


Paul Hunt 2010

I've ordered a new pin, lock nut, latch spring, and main spring (one that goes around pin). I've printed out your photo, and going to compare to mine tonight.

I think my latch comes to about the same point - half way across hole. I do wonder though how much of an arc my locking arm has compared to yours. I wonder if my locking arm is too worn.

I do have the rubber blocks in the "wings" and when the hood is closed it lines up perfectly with the edge of the wings. If I tighted pin/bolt down more the bonnet/hood will be below the level of the wings/fenders.

About all I know for sure, is that last week the hood popped open on smooth roads, where before it took rough roads to break it loose to safety latch.

I'm just amazed at how something so straight forward and simple mechanically can be causing this much grief and attention. Needless to say I don't drive to far from home.

Thanks for all the comments.
R.W Anderson

I fitted a leather strap to my bonnet. Good thing too as the bonnet catch popped open with the car on the trailer being towed to be registered. The saftey catch probably would have held it but I am glad I didn't have to rely on it. Who knows how long it had been open before we stopped.

I fixed it by unscrewing the pin a little. Doesn't seem to pop open now. But I am still glad of that strap!
Simon Jansen

RW - as a 73 same as mine, and presumably the same grill i.e. the honeycomb, my bonnet is sitting on both the small round buffers on that as well as the large rectangular buffers in the wings. As such it can only be pressed down a tiny amount which is the 'give' in the buffers. If you can press your down 1/2" it can't be touching the buffers, and that is almost certainly your problem or a large part of it anyway. Whilst all new latch parts might work, it might not, and being tight I would rather have exhausted the buffer and movement approach first!
Paul Hunt 2010

Hi,

I must admit that I hadn't fully considered the forces involved if the bonnet (hood) opens at speed. I feel that the plastic inserts themselves are strong enough, but the metal around them may well be bent out of shape as the inserts are ripped out. I will have to re-think the situation and see if I can come up with another solution, as welding, at this point, is not an option, because the bonnet, and the rest of the car, have been finished.

Herb
Herb Adler

I installed new bolt, spring, cup, locking nut on to hood/bonnet last night. I only screwed the bolt in 1/2" or so and secured lock nut. I lowered hood and it latched so tight it surprised me. There is <1/4" movement, and feels very secure.

I have the retangular rubber bumpers in the channels on the wings/fenders; but I have to re-look at the rubber bumpers/buffers that you imply are along the front of the hood/bonnet. My recollection isn't working enough to recall their presence or condition.

Earlier last evening two fellow MG owners commented that they kept "loosening" the bolt to find the sweet spot instead of tightening it up to minimize free play, and once they found the spot, the problem is gone. Some think over tightening brings the cone head of the bolt too tight against the locking plate, which then has a tendency to release.

Time will tell.

Thanks for all the kind suggestions.

BobA (winter is returning to MN, so repairs are slowing down the next few days!)

R.W Anderson

Too tight against the latch will cause problems if it is stopping the latch coming back as far as it should.

The other buffers I mentioned are along the top of the grill surround, not on the bonnet by the way. The turned-over flange of the bonnet closes down onto them. You can just about see one of the two in this picture from Clausager.

Paul Hunt 2010

This thread was discussed between 27/04/2010 and 08/05/2010

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now