I have a 2007 XC90. I've replaced the Nivomat shocks in the spring of 2018 / about 70k miles ago. I bought the Nivomats at FCP Euro -- so they have a lifetime warranty.

A rear coil spring broke and I can't get the top nut off the Nivomat shock. It's rusted really bad. I broke a Torx trying to hold the shaft while turning the nut. Now the Torx splines in the shock shaft are getting really bad in the shaft. An impact on the nut just makes the whole shaft spin.
1. Is there another way, other than cutting off the top nut to get this thing off?
2. I'm wondering if I cut the nut off - and maybe damage the shaft of the strut, if FCP Euro will still give me reimbursement. Has anyone had to anything similar and still have FCP Euro honor the lifetime warranty?

Thanks.

 

First, did you soak the threads with a penetrating oil, like PB Blaster or WD40 (or better yet; Aerokroil?) That should always be the first step, letting it soak overnight, for rusted fasteners.

If that doesn't work, I've heard others use vice grips on the shaft to keep it from spinning, but that is usually on blown shocks/struts that are being replaced so there's no concern over damaging the shaft.

 

+1 on grabbing the upper part of the shaft with vise-grips. I've resorted to that in the past.

 

They're Nivomat shocks with a rubber boot covering the shaft. They're expensive and they still work. I just need to get it out to replace the coil spring.
I'm not sure how to get that boot out of the way to grab the shaft.
Is it possible with the Nivomats without ruining them?

I was thinking about taking a Dremel and cut into the nut on a couple sides and see if I can break the nut off the threads. Obviously, being careful to not cut into the threads of the shaft.

 

you only need to drill out one side - then tap on the nut to crack the thread loose or force a blade or punch into the drill hole to stretch the nut just a bit to allow it to loosen. are you able to grab some of the top of the rod?

 

Thanks for the idea of just drilling first @mt6127 That sounds like a good first option.
There's not enough thread to grab the top of the shaft.
The Torx splines should be intact enough to hold the shaft if the resistance isn't too much.

If I can get the nut off, I'll clean up the threads, run a die over the threads to make sure I can tighten it back down when reassembling.

I'll be trying this after work today.

 

I'd start by buying some new carbide bits so you can start with a small hole and work your way up. yep, worked on plenty of rusty cars here in New England...

 

Didn't work. I had to cut off the shaft.
It's like the nut and shaft were frozen together somehow. Chemical/salt reaction here from our MN winters?
I'm buying a new Nivomat to replace it.

 

oh well. as an fyi, another hack for rusty bolts is to apply heat then chill (ie get the bolt red hot with a torch to expand it, then spritz with water to quickly contract it to crack the rust bonds. just need to be careful around rubber bits, fuel lines lol. Also you can use PB Blaster well in advance of your projects in the future. For example, a week before getting your car in for an alignment, spray the tie rod threads with PB and let it soak in - the driving vibrations will help move the oil along as well. Your shop will thank you :-)

 

Funny you mention tie rods. I had it in for an alignment a month ago due to really bad tire wear on the front insides. The shop said it needs ball joints and tie rods. I think just one of the tie rods is bad though. A ball joint is definitely ready to fail - lots of play. I bought 2 ball joints and 2 tie rods and was just going to replace them. Everything is so rusty. I'm thinking about taking it in and see if a shop will use my parts and how much they'll charge.
I did replace ball joints 5 years ago, so I should be able to do that again. The tie rods have never been replaced (200k miles) and are super rusty.

BTY - I contacted FCP Euro before ordering the new shock. They said they'd cover it under the lifetime warranty.