Raising the bonnet release height - how? ******** FIXED!

[Tr4aJim]

Folks, I have been living with an issue on my TR4A for quite awhile, that I decided to finally get around to addressing. When I release the bonnet, it releases fine, but it pops up barely enough to get fingers under the rear edge to lift it.
 

I could see that the latch bracket had slotted holes, so I was all set to just loosen the bolts, slide the bracket up a bit, and job done. Not a chance! I quickly noticed that only the top holes are slotted (what’s the point of that?), so no vertical adjustments are possible.

So is there a way to adjust how high the bonnet will release? I tried changing the length of the bonnet catch rod (with my heart in my mouth that I’d mess it up and it wouldn’t reopen), but that just seemed to change the spring tension, not the release height. 

Am I missing something here? Has anyone else dealt with this issue?

Thanks 

Jim

Edited March 1, 2022 by Tr4aJim

[stuart]

1 hour ago, Tr4aJim said:

Folks, I have been living with an issue on my TR4A for quite awhile, that I decided to finally get around to addressing. When I release the bonnet, it releases fine, but it pops up barely enough to get fingers under the rear edge to lift it.
 

I could see that the latch bracket had slotted holes, so I was all set to just loosen the bolts, slide the bracket up a bit, and job done. Not a chance! I quickly noticed that only the top holes are slotted (what’s the point of that?), so no vertical adjustments are possible.

So is there a way to adjust how high the bonnet will release? I tried changing the length of the bonnet catch rod (with my heart in my mouth that I’d mess it up and it wouldn’t reopen), but that just seemed to change the spring tension, not the release height. 

Am I missing something here? Has anyone else dealt with this issue?

Thanks 

Jim

Sounds just like a tired spring really as its only going to lift as far as the height of the spring anyway, do you have a safety hook on yours?

Stuart.

[Tr4aJim]

Hi Stuart. The latch and spring assemblies are only a few years old, so I wouldn’t think they’re worn or the spring is weak (though who can tell with replacement parts). The spring assembly is the 4A type without the hook. When I release the bonnet, the bottom edge of the rear bonnet flange is just about flush with the body in front of the windscreen.

I took some measurements:

The spring assembly is 3 inches long. 
The distance from the bottom of the spring assembly to the bottom of the rear bonnet flange is 3.5 inches. 
The distance from the top of the bracket (where the spring assembly engages), to the top of the body in front of the windscreen, is 3.5 inches. 

So with the limited panel/bonnet gap, and I expect the weight of the bonnet compresses the spring a bit, that gives me less than 1/2 inch to get my fingers under the bonnet flange to lift it. 

I’m really tempted to elongate the bottom holes of the bracket, so I can raise it even a quarter inch, but it should work as supplied. 

Jim

[Z320]

Hi Jim,

opening my bonnet the gap to the mudguard is about 22 -23 mm

Ciao, Marco

Edited February 27, 2022 by Z320

[keith1948]

Hello Jim

Make sure the end of the spring lines up with the bulkhead catch. There are 2 bolts holding the spring catch to the bonnet. Loosen these a bit and first make sure it lines up side to side. Second look from the side of the bonnet and see if it lines up and if necessary move it forwards or backwards. Sometimes this is all that is needed. I think you will find that there is enough movement of the bracket to get it in line.

Then check the 2 rubber cones that locate the corners of the bonnet at the bulkhead end. Easiest way to position them is to loosen them, push down the bonnet so they are positioned exactly and then tighten them.

I have fixed a few bonnets that didn't open properly as you have described simply by adjusting the spring position so it locates centrally in the bulkhead part of the fitting. You can adjust the spring length by screwing the central rod up or down. You first have to loosen the locknut at the bonnet end of the spring by inserting an open ended spanner through the spring onto the locknut. Don't unscrew it too far though. Remember to retighten the locknut.

If non of this works then you may need to slightly adjust the hinges at the front of the bonnet if the bonnet is catching on the bulkhead. To do this remove the headlamp units so you can access the hinge bolts when the bonnet is closed. Loosen the various hinge bolts a bit and pull or push the bonnet to line it up with even gaps all around. Tighten the nuts and replace the headlamps. Recheck the spring alignment as before.

Good luck

Keith

p.s. If you simple lower the bonnet so it rests on the spring what is the gap like then? If it is ok then it is the adjustment as I have described. If the gap is too small then you may need to raise the bulkhead part of the catch a fraction. You should be able to get your fingers under the edge if you just let the bonnet rest on the spring.

Edited February 27, 2022 by keith1948
extra info

[keith1948]

Hello Jim

just done some measurements on my 4A. The bonnet spring length is 3 1/4 inch between bracket and end of spring assembly.

With the bonnet resting on the spring it is 1 1/4 inch from top of bonnet to top of the flap that lets the air in.

From the top of the bracket of the closing mechanism to the top of the air flap is 3 inch. From the top of the bracket to the underside of the drainage channel in front of the screen is 2 inches.

So it looks like your latch assembly is about 1/2 inch too low.

Try to move it up as far as you can. Is it possible to put a spacer between the spring assembly and bonnet? Mine doesn't have one but that might give you a bit more 'lift' to the bonnet.

Keith

[Z320]

Hi Tim,

if the bonnet closed is in the correct height in relation to the mudguard the latch assembly is in the corret height on the car body.

My idea is the position of the gap on the bolt (holding the bonnet losed) and the length of the bold longer as the position of the gap (which limits the length of the expanding spring). My spring is max about 85 mm long. 

Ciao, Marco

Edited February 28, 2022 by Z320

[Z320]

I make a photo later about what I mean.

Edited February 28, 2022 by Z320

[Tr4aJim]

Hi Keith. 
The bracket and the the spring assembly seem to be aligned well. I put tape over the round part of the bracket where the spring engages, and some white grease on the spring assembly. Closing the bonnet lightly, the grease mark was centered in the bracket circle. I also checked how far the spring assembly was extended. It’s unscrewed just enough to still engage it’s cross bracket, so it’s as far as it will go.

So I did my measurements again.  If I measure the distance from the top of the bracket to the top of the scuttle panel,  measured closest to the bulkhead, it’s 2 3/4 inches. However if I take the same measurement, but from the circular point on the bracket where the spring engages, it’s 3 inches to the top of the scuttle (the same as the length of the full spring assembly, from the tip to the back of the cross bracket). So if that’s the case I’d think the bonnet should sit proud of the scuttle 1.5 inches (the distance from the top of the spring bracket to the top of the bonnet.

I did another test where I clamped the bonnet catch mechanism fully disengaged. Then I slowly lowered the bonnet thinking that at some point the spring would support the bonnet. It didn’t. The bonnet went all the way down until it was flush with the scuttle panel (sitting on the rubber cones). Shouldn’t the spring have held the bonnet proud of the scuttle?
 
If I do that same test with the bonnet catch enabled. The bonnet goes down until it’s about 1/4 inch proud of the scuttle. I’m thinking that maybe it’s just the friction between the bonnet catch and the cone end of the spring assembly that holding it, and not the spring.

As I mentioned to Stuart above, the spring and bracket assemblies are only a few years old, but maybe the repro spring assembly is junk.

Marco, not sure I followed that, but looking forward to the pictures.

Jim

 

Edited February 28, 2022 by Tr4aJim

[stuart]

That still sounds like the spring isnt up to the job, mine comes up with a fairly substantial bounce when I pull the release. It also sounds as if you dont have the pin adjusted right if the bonnet sits proud of the scuttle when the catch is engaged.

Stuart.

[Tr4aJim]

Stuart, sorry I guess I wasn’t clear. If the bonnet is fully engaged with the catch, the the bonnet and scuttle are flush. When I release the catch, the bonnet only rises about 1/4 inch above the scuttle. It definitely does not pop up as you describe.
So I think you are right and the spring is not doing it’s job. Now I have to either find a stronger spring or get a whole new spring assembly and hope it’s better than this one.

If I do decide to get a replacement spring assembly, do you have any preference of the 4A vs TR6 types (Moss US only offers the latter, but the Roadster Factory offers both).

Jim

Edited February 28, 2022 by Tr4aJim

[Z320]

Hi Tim,

sorry my poor explanation, here are the photos (sorry, no pictures).

This is where the latch is situated, the bolt goes through the hole in the center and the latch engages it from behind the head of the bolt.

This is the spring, fully expanded about 85 mm long, ending with a about 25 mm long steel "cup".

The expansion is limited by rear end of the cup touching the head of the bolt from behind.

Next is the spring compessed about the 25 mm, the lenght of the steel "cup", this is the way the bonnet opens.

To compress the spring manual to get the spanner between was not easy....

Possibly your repro part has no "cup"? Or a shorter one?

Ciao, Marco

[Tr4aJim]

Thanks Marco. Yes that is the configuration I have. All my tests and conversations lead me to believe the issue is with the spring being too weak. I’m going to try and find a stiffer spring that will fit, or maybe a second spring to fit inside the first. Last resort will be to buy a new spring assembly.

Jim

[stuart]

TBH I would go with the TRF offering as they do pretty good stuff.

Stuart.

[Tr4aJim]

Folks - It’s fixed!!! 

I disassembled the spring assembly and took the spring to a local “old fashion” hardware store (you know, the kind with everything in bins and smells great). Luckily they had a spring that had the same wire size, overall diameter, and was an inch longer. 

I put the new spring back in the assembly, mounted it, and gently laid the bonnet down, resting on the spring. The top of the bonnet was now 1.5 inches off the top of the scuttle! 

I closed the bonnet, released it, and it popped up like a shot, again 1.5 inches above the scuttle!! 
 

Thanks, as always, for all the help and suggestions!

Jim

[BlueTR3A-5EKT]

23 hours ago, Tr4aJim said:

Folks - It’s fixed!!! 

I disassembled the spring assembly and took the spring to a local “old fashion” hardware store (you know, the kind with everything in bins and smells great). Luckily they had a spring that had the same wire size, overall diameter, and was an inch longer. 

I put the new spring back in the assembly, mounted it, and gently laid the bonnet down, resting on the spring. The top of the bonnet was now 1.5 inches off the top of the scuttle! 

I closed the bonnet, released it, and it popped up like a shot, again 1.5 inches above the scuttle!! 
 

Thanks, as always, for all the help and suggestions!

Jim

Great outcome.

Wish I could find an old fashioned hardware shop here in London.  
They all got pushed out of business by alleged non tax payers like Amazon.   Not to mention the big DIY sheds like B&Q (=your Harbour Freight) that only want to sell packets of ‘stuff’ that their marketing/accountant depts have told them the buying public want.  Or should i say maximises profit.

Edited March 2, 2022 by BlueTR3A-5EKT

[Tr4aJim]

Yeah, I’m very lucky to have two old style hardware stores nearby. Most have been replaced here by Home Depot or Lowes.
What’s even worse are the “chain” auto parts stores that have driven all the independent ones out. 

cheers

Jim

[BlueTR3A-5EKT]

22 minutes ago, Tr4aJim said:

Yeah, I’m very lucky to have two old style hardware stores nearby. Most have been replaced here by Home Depot or Lowes.
What’s even worse are the “chain” auto parts stores that have driven all the independent ones out. 

cheers

Jim

Note to self…. Try to use the independent shops first even if they might be a tad more expensive.