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B5 Avant Rear brake caliper guide pins....do they need lubricating?

Discussion in 'A4/S4 forum(B5 Chassis)' started by Nessy, Oct 13, 2011.

  1. Nessy
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    Nessy VW + Audi mad

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    [Oct 13, 2011]
    I've got an issue with my car which I'm beginning to think might be of my own making......
    Every 6 months or so I'm finding that the rear pads appear to be sticking slightly on (usually given away by the smell!) and when I remove the pads I find that 1 or more of each guide pin that the caliper is supposed to float/slide on is well and truly seized in the caliper carrier!
    Now, in the past I've just unbolted the caliper, removed the guide pins , cleaned them thoroughly and after lightly greasing them, put them back into the caliper carrier.........
    Now, I don't think my calipers are sticking (famous last words I know), but I'm now wondering if the act of greasing these guide pins (with a small amount of copper grease) is whats causing the problem?
    Over time, I'm theorising that this grease is becoming a solid gunk (the discs/pads do get pretty hot don't they) and it is this that is causing the caliper no longer to slide effectively.
    The guide pin is very tight into the caliper carrier at the best of times, so the amount of grease applied is very minimal, but now I'm wondering if the whole guide pin/caliper carrier assembly should just be totally clean , devoid of any lubricant?
    The Haynes mentions nothing about the guide pins really (other than to use new guide pin bolts), the same goes for Elsawin.
    Can anyone advise me about these pins?
    I've got a plan on the weekend to get both rear wheels off and totally degrease these caliper guide pins,to save potential future hassle but I'd be a lot happier knowing whether they should be lubricated or not..........
    Thanks!
    Last edited: Oct 13, 2011
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  3. AndyC
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    AndyC Moderator Staff Member Moderator

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    [Oct 13, 2011]
    I use Moly lube for mine, and have the same problem...

    I think they are just a high service item..

    I even had a new one a new months back and that is now squeaking a little.

    I would always use lube.... but swamp it, so there is loads on there..

    Andy
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  4. Nessy
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    Nessy VW + Audi mad

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    [Oct 13, 2011]
    Thanks for the reply, but the pin (even when cleaned off etc) is a very cosy fit into the caliper carrier so its very hard (unless you're using something very runny like Molyslip) to get much grease in there.......
    That's why I think that the thin layer of grease that I do get in there soon gets cooked and effectively causes the pin to seize?
    I can't help think that running the pins dry is better than having this issue every few months?
    I've got some powdered graphite here in a tube for easy dispensing , so am wondering if cleaned pins and caliper carriers + graphite might be the solution?

    Cheers.
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  5. a3tdi2001
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    a3tdi2001 Member

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    [Oct 13, 2011]
    Last edited: Oct 13, 2011
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  6. Nessy
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    Nessy VW + Audi mad

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    [Oct 13, 2011]
    Cheers, funnily enough I did one side of the car this afternoon as that appeared to be sticking the most (need car for a meeting tomorrow so some emergency maintenance was essential) and used some silicone grease that I had lying around that I bought to lubricate my sunroof runners (its great stuff).
    I'm still more inclined to clean both sides out though and either run them dry or with powdered graphite...at least I know I'm not alone!
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  7. a3tdi2001
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    a3tdi2001 Member

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    [Oct 13, 2011]
    Wouldn't run them dry with the heat that is in the area. Think how an alloy wheel welds itself to the brake disc if you don't put a smear of grease on the mating face. I'd stick to the silicone grease. I've been two years now without any grief.
    Last edited: Oct 13, 2011
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  8. Nessy
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    Nessy VW + Audi mad

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    [Oct 14, 2011]
    Thanks, that's making me think twice now about running them dry!
    The odd thing is though, have had this car for almost 6 years and its only in the last 18 months that I've had issues with these pins ...very odd!
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  9. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 14, 2011]
    Yeh, i've had the same issue a few times, and i think its down to using copper grease or LM instead of the proper stuff.

    The OEM grease for sliders is white, so i presume its silicone grease as mentioned above. I used silicone stuff the last time and the caliper immediately felt much "freer" in the carrier than when using copper or LM grease.
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  10. a3tdi2001
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    a3tdi2001 Member

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    [Oct 14, 2011]
    Using copper or moly grease near rubber or plastic is not advisable as it swells the rubber and causes friction.
    I use silicone grease anywhere that has rubber or plastic eg, caliper pistons, sliders, even works well on bootlid and bonnet struts. Really noticed the difference recently when I thought my mountain bike forks were knackered but changed from moly to silicone grease on the stanchions and they're as good as new again.
    Last edited: Oct 14, 2011
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  11. Nessy
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    Nessy VW + Audi mad

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    [Oct 23, 2011]
    As an update, I've sorted out the issue.....
    Turns out that the caliper handbrake mechanism was sticking, so even when the brake was fully released the pads were still partially binding on the disc.
    This was causing this particular wheel to slightly overheat and so the grease on the guide pin was becoming cooked!
    I had been wondering why my fuel economy hadn't been as good recently....!
    A replacement caliper later , along with new rear pads and all is well again.
    Am now using silicone grease on the pins, so touch wood there'll be no more trouble.....
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  12. AndyC
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    AndyC Moderator Staff Member Moderator

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    [Oct 23, 2011]
    I will be honest.... I have Moly grease on mine and I pulled them apart after about 6 months and they were perfect. Even on the original caliper

    I had exactly the same problem with my calipers with the handbrake mech seizing....

    Glad you got it sorted.
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  13. Geeman
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    Geeman Low Life

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    [Oct 24, 2011]
    Beware of these sliders!

    I just had two brand new calipers put on the back of my S4 as they had 'seized' on.

    I took the new ones off this weekend as we did the rear bearings to find that the garage that had fitted them had not lubed the pins back up again and were bone dry/brown with rust dust and one had seized on again!

    As you can imagine, I was less than impressed.
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  14. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 24, 2011]
    And this is why my car never goes near a garage.

    We discovered when we did craigs reshell that the garage that changed the wheel bearing on the rear of his S4 had clamped the stainless braided brake hose with a pair of mole grips.

    No idea why, as you dont need to touch the hydraulic circuit to remove the upright, but surely everyone knows you dont use bloody mole grips on a stainless brake line ffs.
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  15. AndyC
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    AndyC Moderator Staff Member Moderator

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    [Oct 24, 2011]
    Fecking hell, what a bunch of "yeee haaaaaar"

    I have hose ends I use for braided hoses as of course you cant clamp the damn things!! JESUS!
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  16. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 24, 2011]
    yeh. mole grips on a rubber hose works, but even thats a bit harsh tbh. Something you might do in a pinch when DIYing it but not something you'd expect from a garage.
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  17. AndyC
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    AndyC Moderator Staff Member Moderator

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    [Oct 24, 2011]
    proper hose clamps are better than molies
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  18. Nessy
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    Nessy VW + Audi mad

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    [Oct 26, 2011]
    Looking into the lubrication issue again, I noticed on my ancient PC-installed copy of an electonic parts catalogue (is its name still banned on here?,lol?) that there was an item listed G 000 650 described as 'lubrication paste' on the same page as the rear caliper and carrier.
    Google brought up the info that it was a very high temperature grease for the sliders , and that there is an equivalent Febi-Bilstein product too (have mislaid the part number though).
    Looking on Ebay USA though it was full of 'ultra disc brake lube' made by Permatex amongst others, which appears to be exactly what we need ie very high temp grease for brake calipers, sadly there don't currently appear to be any European suppliers..
    In the meantime I still continue to run silicone grease on my sliders, but as it was primarily designed for sunroof track lubrication I worry about how durable its going to be.....
    Last edited: Oct 26, 2011
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  19. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Oct 26, 2011]
    i tend to use a smidge of copper and then moly, works for me. RRG is for lubing rubber parts, i have used it on pistons and the like as it supposed to be for
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