hood torsion spring mechanism, break and renew

[deQuincey]

last week a thread with a similar issue comments the fact that the hood mechanism suffers from age

you might have different causes for this break, here is mine:

some days ago i found that the left compass arm of my hood mechanism was bent inwards

i checked it and i found this: paint was off the place and a slight sign of a crack was there

i was surprised because two years ago i renewed the system, using the old parts i cleaned them and repainted, using rust inhibitor, adn so on

then the mentioned thread came and i started looking for solutions

so i found and ordered the part

while waiting, and in order to use the car i thought of a solution:

but then i w:as worried about it banging something and i decided to dissasemble

see the crack:

 

[61porsche]

FYI- I welded mine back in place and refinished. Looks like yours started at the weld and progressed.

 

[deQuincey]

FYI- I welded mine back in place and refinished. Looks like yours started at the weld and progressed.

+1, what you can see is the progression of the crack within 2 days
i am going to have it re-welded and probably adding a bushing to increase the thickness of the tube section

 

[pamp]

Yeah,
I did mine on the shop floor and re-finished as well. The trick was to get the spring unloaded as I recall....

 

[deQuincey]

to anyone that has this problem and is considering buying the replacement part from bmw, here you are the contents

yes, once you see that the part is available the question is, ...and what is comprised within that reference ?

well, everything, except from the fixing screws, the rest is included, bar, arms, springs, supports,...

pinted in black

compare old and new, the inner support looks so ....accurate !

hope that to know this helps you identify what you buy...

 

[fredp]

Can you let me know the part numbers you ordered to get the "kit"? Thanks

 

[deQuincey]

Can you let me know the part numbers you ordered to get the "kit"? Thanks

you can see in the first pic, white tag with bumw emblem on it :-D

 

[deQuincey]

well, i bought the replacement bar some time ago, but hadn´t the time to put it on the car, i have checked it, and it seems that as it is in new condition, the torsion spring is stronger thus i need to exert more force to place it in position,

so i decided to fabricate a tool ad-hoc to pre-stress the bars, e voila:



this allows you to rotate the end tip until is positioned and then you can fix the "L" shaped plate that blocks the spring

 

[bavbob]

I think this is a design flaw to start with so being proactive is key. We need to watch for the welds cracking and repair at first sign. Mine was exactly the same and I re-welded it, so far so good. I bet if we stopped staring at what is under the hood, the thing would actually last longer.

 

[m_thompson]

I rewelded mine 31 years ago and it has been fine since then.

 

[deQuincey]

so then after preparing the tool i place the bar in a vice and :



loosing the bolts of the retaining plate i place the tool



and started tensioning, until the position was reached and then i placed the retaining plate and secure it with the bolts



i found this the only way to do this process, prepare and tension the mechanism in the table, and then move it to the car















incidentally, i used a double retaining plate, by reusing the old one too and placing longer bolts, it gives an extra support to avoid the retainer being blent

 

[deQuincey]

i found this to be the only way of doing it, unfortunately the tension that has to be performed to the bar torsion springs is pretty high so you have to be very careful and to maintain the aluminium blocks inside the tube as much as possible, so when the tension is exerted they will be kept stable there like mouse traps

then you have to move very carefully towards the car hood (maintaining it open with a long stick

you place it in posistion and then you fix the 2+2 hexagonal headed bolts

then another moment to demonstrate your strength, you have to pull the arm out to be able to place the fixing bolts near the battery on the left side and the other one opposite on the right (only the first one will be hard to place in position)

 

[oilcan93]

Dequincey, I may be contacting you for a little help along the way as I take up this endeavor soon. I heard this is a somewhat difficult undertaking from SFDon who normally does my work for me. But i live in Hawaii and have to fly him out every time I need something done which I'm trying to avoid for a "minor" task like this. Someone closed the hood on my couple and bent the arm on the left the wrong direction as it closed forcing exactly the same tear that you had.
My first question is where did you get that wrench that you have bracing the force of the spring? The one that has the two bolts passing right through it. That looks necessary to performing this task while keeping tension on the spring. By ordering part # 41611814312 will that include all hardware that I need for the task or will I have to order the brackets, springs, appropriate washers, etc...separately. Thank you in advance for the knowledge.

 

[HB Chris]

I doubt it's possible to force that arm the wrong way. Theses bars break from old age unfortunately. Get a piece of steel bar, drill two holes in it and bolt to mounting bracket, place on floor and bend arm until it slips under locating bracket.

 

[oilcan93]

Good advice and thank you for it! But unfortunately, that's exactly what happened to damage it. I watched from the driver's seat as it buckled forward instead of back to my horror. Got out and opened the hood immediately to find the damage already done. I just didn't think it would be so difficult to repair. The silver lining is that it sounds like I would have had to do this repair eventually anyway due to the nature of the beast.

 

[deQuincey]

Dequincey, I may be contacting you for a little help along the way as I take up this endeavor soon. I heard this is a somewhat difficult undertaking from SFDon who normally does my work for me. But i live in Hawaii and have to fly him out every time I need something done which I'm trying to avoid for a "minor" task like this. Someone closed the hood on my couple and bent the arm on the left the wrong direction as it closed forcing exactly the same tear that you had.
My first question is where did you get that wrench that you have bracing the force of the spring? The one that has the two bolts passing right through it. That looks necessary to performing this task while keeping tension on the spring. By ordering part # 41611814312 will that include all hardware that I need for the task or will I have to order the brackets, springs, appropriate washers, etc...separately. Thank you in advance for the knowledge.

i answered your PM yesterday

i made the tool by myself, it is essential to place it firmly and safely in a table, look at my setup, it is a mousetrap mechanism, it will hurt you if not carefully done

the bmw ref includes all the parts

 

[jmackro]

..... it will hurt you if not carefully done

I noticed in deQuincey's photos (one of which is reproduced below) that he used two of the "L" shaped brackets on each side. I also found it necessary to stack two brackets; a fresh spring exerts enough force to deform a single "L" bracket.

Watch out for this! If you just use a single bracket, it will deform slowly and eventually the arm will snap like a rat trap. Don't you be the rat!

 

[oilcan93]

I'm getting ready to do this repair. What is the part# for the L bracket and I will order and extra set?

 

[deQuincey]

I'm getting ready to do this repair. What is the part# for the L bracket and I will order and extra set?

as far as i know that part alone is unobtabium, you should use your actual ones with the new ones that came in the set
on the contrary, make one by yourself

 

[jmackro]

I'm getting ready to do this repair. What is the part# for the L bracket and I will order and extra set?

As deQuincey wrote, you will have two pairs once you buy a new torsion arm & spring assembly. That is, as long as you haven't already thrown out your old assembly!

But as deQuincey went on to say, the "belt and suspenders" solution would be to mill new L brackets out of 1/4" chrome moly steel.