Little suspension Issue

[omendamo]

I had my car in for MOT a few months ago and recieved an advisory for the rear suspension missing a dust cover of some sort. It wasn't at a dealer so they said they couldn't source the part.

 

I forgot all about it, until recently when I noticed a metallic rattling coming from ther rear suspension. Looking over the wheel I could see a circular metal cover was hanging loose. Presuming this went ontop of the rubbery cover on the suspension I pushed it back on and it fit snugly. A week or so later it's dropped off again.

 

Searching about I can't seem to find anyone explaining the same issue. What's wrong and how do I fix it?

[banzaiman]

Do you mean this cover? This is mine and i've bought a new one to go on but the ring at the top which is where i presume it fits is all corroded and white. 

 

Edited 31 October, 2014 by banzaiman

[trundlenut]

Do you mean this cover? This is mine and i've bought a new one to go on but the ring at the top which is where i presume it fits is all corroded and white.

That's the bump stop. The foam disintegrates then the protective cover for the shock absorber falls down. You need yo replace the foam bump stop not the plastic cover.

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[omendamo]

Thanks both, so do I need a kit like: http://www.ebay.co.uk/itm/SKODA-OCTAVIA-VW-BORA-2-REAR-SHOCK-ABSORBER-PROTECTORS-BUMP-STOP-KITS-/300721905074?_trksid=p2054897.l4275

[trundlenut]

Probably. On the mkI the foam bits were available separately. Didn't need to replace the plastic bits, just slid them onto the new bump stops and refitted them.

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[omendamo]

Oops yea I've realised I looked at MK1 and not MK2.

 

Is this more appropriate? http://www.skodaparts.com/product/octavia-a5-rear-bump-stop-2004--33069

[trundlenut]

They look OK. One thing I'm not sure of is whether the top mount bolts are stretch bolts. If they are they will need to be replaced.

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[omendamo]

Thanks, how would I tell?

[trundlenut]

You need a workshop manual, or the Haynes manual.

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[trundlenut]

Just been and had a look. My Haynes reckons both the top mount bolts and the one at the bottom of the shocker are stretch bolts and need to be replaced.

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[brad1.8T]

Just been and had a look. My Haynes reckons both the top mount bolts and the one at the bottom of the shocker are stretch bolts and need to be replaced.

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Wouldn't bother unless they are badly corroded.  Just screw them in tight.

[trundlenut]

Wouldn't bother unless they are badly corroded. Just screw them in tight.

They're stretch bolts!

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[dohboy78]

Out of curiosity... What is the purpose of a stretch bolt??

[trundlenut]

Out of curiosity... What is the purpose of a stretch bolt??

I think..

In order to ensure the bolt does not come undone, when you tighten them, the second stage stretches the bolt thus securing it. But if you reuse them they have already been stretched and retightening can then over stretch them and cause them to snap.

This has happened where the stretch bolts on the engine mountings have been reused after a cambelt change.

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[brad1.8T]

They're stretch bolts!

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You are probably right (they are stretch bolts).

 

Maybe I'm not anal enough about these things but I've had my front & rear suspension apart twice.  Once at 95,000km to fit Eibachs & again at 110,000km to fit Koni Yellows.  I didn't replace the bolts.  I did them up until my calibrated elbow told me they were tight enough.  Nothing has broken, nothing has come undone.  If I was buying new stuff I'd go to the specialist bolt shop  & buy grade8 std bolts or similar so I didn't have to faff about with stretch bolts.

 

If it was a "mission critical" bolt like a conrod or head bolt bolt I'd buy new ones.

 

Keep in mind that some stretch bolts are multi-use (some conrod bolts are stretch bolts but can be re-torqued 8 times).

 

Out of curiosity... What is the purpose of a stretch bolt??

Stretch bolts are also known as torque to yield fasteners.  They are designed to maximise clamp force & ensure it is consistent among multiple fasteners.  This is really important in high stress / shear / load situations.

 

This might help explain it better  http://freeasestudyguides.com/a1_4.html

 

I'll leave it up to you to decide if for the application you can re-use the fasteners or not. 

 

Last time I looked there was about AUD200 (GBP130?) of one time use TTY fasteners in the front & rear suspension - at least that's what they charge down here for 18-20 fasteners.  I think it's a bit of a rip.

[trundlenut]

When I did the bump stops on my old Octavia I think to bolts came to about £10 for the six of them.

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[wiilydog]

I replaced mine when I did my rear shocks

as they were a bit rusty and think were only a couple of pounds each from TPS. Vw seems to advise to use stretch bolts once only.