UNF Helicoil replacement required to lower wishbone

[Brakebuster]

while rolling around under the XJS for the gearbox install , and now the exhaust manifold blow, i have noticed one of the spring pan bolts not fully tight, and it does have a spring washer on it, while trying to nip it up it doesn't feel right and then pops back down , conclusion , a stripped thread in the lower wishbone , as the thread on the bolt is ok ,

darn....

been scratching my head about this one, as there was no way i wanted to drop the front subframe to remove the wishbone bolt etc,but the work is critical to safety before i drive her again, so i decided to buy a helicoil kit to replace the stripped thread in the casting

this involves using the kits drill to remove the old thread and get back to good metal , tap the hole to allow a ' helicoil ' to be installed that will accept the original bolt , and all this can be done while the wishbone is still on the car with the spring pan in place

the thread size is 3/8 UNF , and i could have just bought a kit for that size, but decided to buy a kit from 1/4 to 5/8 with all the bits, taps insertion tools and break off tools and a load of helicoils of differing sizes to carry out any thread repair on the car for UNF , and at £70 , i don't think it was bad value


just got to do the job now , lol

wish me luck

BB

[poprivet]

Scary, Hopefully all the others will be ok.
A lot of spring pressure trying to force that plate off and not easy to unload the spring while working on it. Take care.

[steve_m]

Good luck!

[Brakebuster]

Scary, Hopefully all the others will be ok.
A lot of spring pressure trying to force that plate off and not easy to unload the spring while working on it. Take care.

the bolt that failed is the back edge, so as you say its taking a lot of pressure, i have removed the bolt fully and the plate hasn't moved any further away from the wishbone, and in total is about 4mm away from the existing spring pressure, the car is way in the air already for other work , and i will push up under the pan to take the pressure and then do the helicoil

all being well , it should go fine,................. famous last words


BB

[ptjs1]

Good luck BB!

You, more than most, fully understand the safety issues associated with that spring installation, so I'm sure you'll do it thoroughly and safely.

I do find tapping threads a quite therapeutic activity. The use of the coarse, medium and fine taps, the gradual to and for motion to carefully get the new thread biting into the metal, the use of lubricating oil, the gentle cleaning of the swarf and the sense of achievement when the new bolt glides smoothly into the new thread; it's all a very satisfying way to spend an hour or two. I don't know enough about helicoils, but are they appropriate for load-bearing situations such as the spring pan, or would you be better off tapping the casting to just take an oversize bolt?

Paul

[Brakebuster]

true , I did consider installing an oversized bolt , but there is no going back if that fails

with the helicoil, you are drilling and tapping a larger hole to take the helicoil to be able to thread the original size bolts back ( I will use a new bolt ) , and if for any reason I need to the helicoil can be removed and another installed for the same application , that's my take on it

and loading will be fine, if not stronger than the original casting as helicoil nuts are already used on the Jag as OE fittings , usually exhaust and manifold nuts and such like

BB

I will be doing this tonight, as the gearbox and new exhaust are now fully installed.......