Cabrio - hunter stress fracture safety warning

[mike woodley]

I have just discovered (today) a stress fracture in a front wishbone pivot bracket on my Cabrio. The car has been on the road since 2003 and has covered 37000 miles. The only indication I had of a problem was a creaking, snicking noise which started about a week ago, when parking up and turning on bumpy ground. I looked for the source of the noise at the time, but did not spot the break. The noise was much worse today and i spent more time on my search and was horrified at what i found. I feel it is something that we all need to check. I have added a couple of photos showing the problem. I will dismantle the suspension tomorrow and post an update.
Has anyone else had this happen?
My problem now is finding a replacement bracket, or is it something that i will have to have fabricated for me?
Any advice appreciated.
Mike.

[dogoncrazy]

Re: Cabrio - hunter stress fracture safety warning

Well done for finding the cause of the noise. I had the same sort of warning with the anti roll bar mount to chassis, which led to members checking theirs and we know were that led.
I suspect that you will have to have it replicated which shouldn't be difficult.
I shall go and give mine a good look over. Thanks for pointing it out.
Alan

[greyV8pete]

Re: Cabrio - hunter stress fracture safety warning

Hi Mike. Thanks for sharing this. Before you remove the nuts give the threads a really good go with a thin wire brush to remove the paint etc. Then a liberal dose of plus gas. I used a combination 10mm spanner with a home made extension as mine were very tight. Use the ring end to start it moving, to avoid rounding off the corners, then the open end to wiggle the nut to and fro rather than just undoing it. Do NOT use a ratchet ring spanner! There is so little clearance before the inner wing there is no way that if it goes tight you will be able to remove it to turn it over to reverse the direction to retighten the nut! Peter.

[dogoncrazy]

Re: Cabrio - hunter stress fracture safety warning

I'd be interested to know whether the pivot bolt removes easily or if it's seized in the bushing. Just a thought!

[milliemarlin]

Re: Cabrio - hunter stress fracture safety warning

Thanks for the tip Mike. I can’t see any problem with mine. Phew!

I have always thought they look a bit on the flimsy side. Especially when compared with the arm that it’s supporting.

Just out of interest does it have a shim of some type behind it? I did consider spacing it out to improve my steering geometry.

Do you use standard rubbery bushes or hard ones? The rubbery Sierra ones seem to be kinder to the metalwork.
Paul

[greyV8pete]

Re: Cabrio - hunter stress fracture safety warning

I'd be interested to know whether the pivot bolt removes easily or if it's seized in the bushing. Just a thought!

When I removed mine to fit Superflex bushes the bolt was an easy clearance fit.

BTW to fit new bushes the brackets and upper suspension wishbone has to be removed complete from the chassis, as the bolts are fitted heads inwards. That’s because there is little clearance between the top wishbone and the chassis upright. Because of this lack of clearance I would avoid making the new bracket out of thicker material. There would also be insufficient bolt thread for the Nyloc nut to grip. Peter.

[greyV8pete]

Re: Cabrio - hunter stress fracture safety warning

Thanks for the tip Mike. I can’t see any problem with mine. Phew!

I have always thought they look a bit on the flimsy side. Especially when compared with the arm that it’s supporting.

Just out of interest does it have a shim of some type behind it? I did consider spacing it out to improve my steering geometry.

Do you use standard rubbery bushes or hard ones? The rubbery Sierra ones seem to be kinder to the metalwork.
Paul

Marlin used E shaped shims between these brackets to adjust front wheel camber. It’s in the build manual IIRC. I removed my shims as they were unnecessary when I fitted the adjustable track control arms. Peter.

[lizbillings]

Re: Cabrio - hunter stress fracture safety warning

There doesn't seem to be a problem with our Sierra based Berlinetta which has been on the road since 1991. We never noticed any problem with Bluebelle after 70000 miles.
The bracket looks strong to me. On the Berlinetta it seems to be 3mm thick.
I wonder whether there is an alignment problem in the manufacture of the wishbone so that the bush is not welded on at the right angle, causing strain on the bracket.
Doug

[cabrioman]

Re: Cabrio - hunter stress fracture safety warning

Hi Mike

Just checked in my left over bits after selling up my Cabrio/Hunter and I have a wishbone bracket, it will need re-painting but but other wise in good nick.

Let me know if you want it.

Cheers

John

[mike woodley]

Re: Cabrio - hunter stress fracture safety warning

Hi John,
That would be great.
I will PM you with my number.
Regards Mike

[mike woodley]

Re: Cabrio - hunter stress fracture safety warning

Update 3/7/21.
First to answer the questions from Doug, Paul & Dogoncrazy. Have checked the wishbone alignment with a piece of 10mm rod, and it drops through both bushes at the same time easily. The brackets are not shimmed & I used the Ford rubbery bushes. The steel insert in the bush was not seized to the mounting bolt. Thanks to Peter Licence for his invaluble advice, and especially to Cabrioman John who has saved the day by finding a pair of replacement brackets, thus saving me the hassle of finding an engineering company to make up replacement brackets. The wonders of the Marlin Owners Club!
I have attached a couple of photo's showing the failed bracket, and also the other bracket which is showing signs of a fracture starting along the edge of the weld to the lower bolt. I have carefully checked the other side wishbone brackets and there are no signs of any problems. I can only conclude that there might be a slight misalignment in the chassis wishbone bracket mounting points which caused the failure. I will see how they line up on reassembly.
Regards Mike

[greyV8pete]

Re: Cabrio - hunter stress fracture safety warning

Hi Mike. Glad that you have been able to source some replacement brackets. Is the crack in the second bracket next to the bottom bolt facing the front of the car, or the top bolt facing towards the chassis turret? Apart from the obvious location of the cracks next to the weld HAZ am still trying to get my head around a possible cause of the failures. Peter.

[chris_cussen]

Re: Cabrio - hunter stress fracture safety warning

Could just be the effect of HAZ, you don't know how far the zone extends.

[greyV8pete]

Re: Cabrio - hunter stress fracture safety warning

Could just be the effect of HAZ, you don't know how far the zone extends.

That’s true. Those welds seem excessively large for a tack weld just to stop the bolt head turning?

[mike woodley]

Re: Cabrio - hunter stress fracture safety warning

Hi Mike. Glad that you have been able to source some replacement brackets. Is the crack in the second bracket next to the bottom bolt facing the front of the car, or the top bolt facing towards the chassis turret? Apart from the obvious location of the cracks next to the weld HAZ am still trying to get my head around a possible cause of the failures. Peter.

Hi Peter,
The crack is on the bottom bolt facing the front of the car.
Regards Mike