Lotus Elan

Rear Shock Absorber Strut Stuck

PostPost by: simonriley11 » Fri Apr 05, 2019 10:53 am

I am rebuilding the suspension on my 1966 S3 DHC and on the LH rear strut the Monroe shock absorber insert appears to be rusted into the housing, the RH strut tube and s/absorber insert were both very rusty on the mating surfaces but at least the shock absorber came out! The LH s/absorber unit can be moved slightly side to side at the top of the strut but it seems as if it's stuck/rusted at the bottom.
I have left the LH assembly overnight in a vertical position with the void between the two surfaces filled with WD40, however that didn't help. I've drilled a 3/8 inch diameter hole in the steel insert in the bottom of the strut (which exposes the bottom of the s/absorber insert) and cleaned out the rust as best I can and I then hit through with a punch but it's till solid. I've now left strut upside down with WD40 topping up the drilled hole but I'm now running out of ideas.
Can anyone help?
Thanks
Simon
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PostPost by: john.p.clegg » Fri Apr 05, 2019 11:38 am

Top eye-bolt in the vice and a rubber/wooden mallet on the casting?

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PostPost by: lotusfan » Fri Apr 05, 2019 11:58 am

Try using Plus Gas instead of WD40. Tap around the outside of the strut tube with a hammer to try and break up the rust.
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PostPost by: simonriley11 » Fri Apr 05, 2019 1:24 pm

Thanks for the replies so far.

I started with a rubber mallet and built up to a 4 pound lump hammer and still no joy.

Regarding dislodging the rust it seems that it is stuck at the bottom of the strut so unfortunately I can't really get at the tube in that area as it's inside the aluminium casting. Don't forget I have exposed the bottom of the s/absorber by drilling a 3/8 inch hole in the bottom of the strut and hitting the bottom of the s/absorberit hard with a drift and a large hammer still won't shift it.

Has anyone else ever had this problem?
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PostPost by: USA64 » Fri Apr 05, 2019 3:06 pm

Why I'm not sure but WD40 doesn't seem to work as a penetrating oil. Switch to a real one or (much as I hate acetone) try acetone/Marvel Mystery Oil mix. I have had success with it when others liquids failed. However, just as important give it time. It might take a few days of soaking. Be patient and avoid destruction.
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PostPost by: h20hamelan » Fri Apr 05, 2019 3:13 pm

I use brake fluid
Sometimes ATF
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PostPost by: john.p.clegg » Fri Apr 05, 2019 3:14 pm

I've got a mix of Acetone and brake fluid...

If you want some Simon?

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PostPost by: types26/36 » Fri Apr 05, 2019 4:17 pm

I would try some heat on it from somthing like a Rothenburger tourch with Mapp Gaz or even a blowlamp,
heat can do wonderful things but be carefull not to get it to hot.......I suppose the oil could heat up and even explode :shock:
https://www.ebay.co.uk/p/Rothenberger-S ... /672098629
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PostPost by: mikealdren » Fri Apr 05, 2019 5:30 pm

USA64 wrote:Why I'm not sure but WD40 doesn't seem to work as a penetrating oil. Switch to a real one or (much as I hate acetone) try acetone/Marvel Mystery Oil mix. I have had success with it when others liquids failed. However, just as important give it time. It might take a few days of soaking. Be patient and avoid destruction.

You're right, WD40 was designed as a Water Displacement product hence WD. There are definitely much better lubricants and penetrating fluids.
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PostPost by: mbell » Fri Apr 05, 2019 6:21 pm

If it is sealed tight you could fit a grease nipple to the bottom hole you have drilled and use a grease gun to pump in grease and push the strut out.

This does require the rust to be bad enough to have formed a seal around the strut to work and will be bit messy to clean up. There is also risk of damaging the tube rather than pushing the strut out. However if you can't get it out your likely heading towards a replacement tube and if the corrosion is bad it might be a sensible thing to do anyway.

After this I expect on rebuild you'll be following the recommendation to add for oil to the tube to avoid rusting and aid damper cooling....
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PostPost by: simonriley11 » Sat Apr 06, 2019 9:50 am

Dear all

Thanks for all the advice so far.

I've ordered some Acetone which I will try next week.

Has anyone ever used any of these 'rust dissolving' liquid treatments? I could pour it from above into the void between the s/absorber strut and the inside of the steel strut housing and leave it to do it's stuff. Looking at the RH strut which came apart I'm pretty sure that it's rust that's causing the problem with the LH.
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PostPost by: USA64 » Sat Apr 06, 2019 11:43 pm

I've used rust dis-solver with success but they were water based and would be displaced by WD40. You might have to cook that out first.
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PostPost by: Frogelan » Sun Apr 07, 2019 4:40 am

Simon

This is not an easy task and probably combining a few methods might work...this is what I have done on other tricky tasks. My secret weapon to derust parts is to use concentrated white vinegar which has the advantage of being both a natural, non-polluting chemical (gloves, eyewear and caution recommended).

https://www.lebriochin.com/soin-de-la-m ... re-16.html

I leave parts to soak for 2-3 days and this type of product has the useful properties of removing rust and hardened grease. It does not seem to damage softer metals such as aluminium, but not do any good to nylon or rubber.

As the product smells of vinegar, for smaller parts I leave them in a 720g jar with the lid on. What I particularly appreciate is that if you forget the mix for a few extra days, no major harm is done.

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PostPost by: StressCraxx » Sun Apr 07, 2019 5:02 am

This is also a non-hamful de-rusting solution. I have used it on several projects and works really well.

https://evapo-rust.com/
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